Fossil

# define shell_read_history(X) linenoiseHistoryLoad(X)
# define shell_write_history(X) linenoiseHistorySave(X)
# define shell_stifle_history(X) linenoiseHistorySetMaxLen(X)
# define shell_readline(X) linenoise(X)

#else

# define shell_read_history(X)
# define shell_write_history(X)
# define shell_stifle_history(X)

# define SHELL_USE_LOCAL_GETLINE 1
#endif

#define isatty(x) 1
#endif

/* ctype macros that work with signed characters */
#define IsSpace(X)  isspace((unsigned char)X)
#define IsDigit(X)  isdigit((unsigned char)X)
#define ToLower(X)  (char)tolower((unsigned char)X)

#if defined(_WIN32) || defined(WIN32)
#include <windows.h>

/* string conversion routines only needed on Win32 */
extern char *sqlite3_win32_unicode_to_utf8(LPCWSTR);
extern char *sqlite3_win32_mbcs_to_utf8_v2(const char *, int);
extern char *sqlite3_win32_utf8_to_mbcs_v2(const char *, int);
#endif

/* On Windows, we normally run with output mode of TEXT so that \n characters
** are automatically translated into \r\n.  However, this behavior needs
** to be disabled in some cases (ex: when generating CSV output and when
** rendering quoted strings that contain \n characters).  The following
** routines take care of that.
*/
#if defined(_WIN32) || defined(WIN32)
static void setBinaryMode(FILE *file, int isOutput){
  if( isOutput ) fflush(file);
  _setmode(_fileno(file), _O_BINARY);
}
static void setTextMode(FILE *file, int isOutput){
  if( isOutput ) fflush(file);
  _setmode(_fileno(file), _O_TEXT);
}
#else
# define setBinaryMode(X,Y)
# define setTextMode(X,Y)
#endif


/* True if the timer is enabled */
static int enableTimer = 0;

/* Return the current wall-clock time */

    getrusage(RUSAGE_SELF, &sBegin);
    iBegin = timeOfDay();
  }
}

/* Return the difference of two time_structs in seconds */
static double timeDiff(struct timeval *pStart, struct timeval *pEnd){
  return (pEnd->tv_usec - pStart->tv_usec)*0.000001 +
         (double)(pEnd->tv_sec - pStart->tv_sec);
}

/*
** Print the timing results.
*/
static void endTimer(void){

#define BEGIN_TIMER beginTimer()
#define END_TIMER endTimer()
#define HAS_TIMER 1

#elif (defined(_WIN32) || defined(WIN32))



/* Saved resource information for the beginning of an operation */
static HANDLE hProcess;
static FILETIME ftKernelBegin;
static FILETIME ftUserBegin;
static sqlite3_int64 ftWallBegin;
typedef BOOL (WINAPI *GETPROCTIMES)(HANDLE, LPFILETIME, LPFILETIME,
                                    LPFILETIME, LPFILETIME);

      HINSTANCE hinstLib = LoadLibrary(TEXT("Kernel32.dll"));
      if( NULL != hinstLib ){
        getProcessTimesAddr =
            (GETPROCTIMES) GetProcAddress(hinstLib, "GetProcessTimes");
        if( NULL != getProcessTimesAddr ){
          return 1;
        }
        FreeLibrary(hinstLib);
      }
    }
  }
  return 0;
}

/*

}

#define BEGIN_TIMER beginTimer()
#define END_TIMER endTimer()
#define HAS_TIMER hasTimer()

#else
#define BEGIN_TIMER
#define END_TIMER
#define HAS_TIMER 0
#endif

/*
** Used to prevent warnings about unused parameters
*/

/*
** Prompt strings. Initialized in main. Settable with
**   .prompt main continue
*/
static char mainPrompt[20];     /* First line prompt. default: "sqlite> "*/
static char continuePrompt[20]; /* Continuation prompt. default: "   ...> " */

/*
** Render output like fprintf().  Except, if the output is going to the
** console and if this is running on a Windows machine, translate the
** output from UTF-8 into MBCS.
*/
#if defined(_WIN32) || defined(WIN32)
void utf8_printf(FILE *out, const char *zFormat, ...){
  va_list ap;
  va_start(ap, zFormat);
  if( stdout_is_console && (out==stdout || out==stderr) ){
    char *z1 = sqlite3_vmprintf(zFormat, ap);
    char *z2 = sqlite3_win32_utf8_to_mbcs_v2(z1, 0);
    sqlite3_free(z1);
    fputs(z2, out);
    sqlite3_free(z2);
  }else{
    vfprintf(out, zFormat, ap);
  }
  va_end(ap);
}
#elif !defined(utf8_printf)
# define utf8_printf fprintf
#endif

/*
** Render output like fprintf().  This should not be used on anything that
** includes string formatting (e.g. "%s").
*/
#if !defined(raw_printf)
# define raw_printf fprintf
#endif

/*
** Write I/O traces to the following stream.
*/
#ifdef SQLITE_ENABLE_IOTRACE
static FILE *iotrace = 0;
#endif

static void SQLITE_CDECL iotracePrintf(const char *zFormat, ...){
  va_list ap;
  char *z;
  if( iotrace==0 ) return;
  va_start(ap, zFormat);
  z = sqlite3_vmprintf(zFormat, ap);
  va_end(ap);
  utf8_printf(iotrace, "%s", z);
  sqlite3_free(z);
}
#endif


/*
** Determines if a string is a number of not.

    while( IsDigit(*z) ){ z++; }
    if( realnum ) *realnum = 1;
  }
  return *z==0;
}

/*
** A global char* and an SQL function to access its current value
** from within an SQL statement. This program used to use the
** sqlite_exec_printf() API to substitue a string into an SQL statement.
** The correct way to do this with sqlite3 is to use the bind API, but
** since the shell is built around the callback paradigm it would be a lot
** of work. Instead just use this hack, which is quite harmless.
*/
static const char *zShellStatic = 0;
static void shellstaticFunc(

      n--;
      if( n>0 && zLine[n-1]=='\r' ) n--;
      zLine[n] = 0;
      break;
    }
  }
#if defined(_WIN32) || defined(WIN32)
  /* For interactive input on Windows systems, translate the
  ** multi-byte characterset characters into UTF-8. */
  if( stdin_is_interactive ){

    char *zTrans = sqlite3_win32_mbcs_to_utf8_v2(zLine, 0);
    if( zTrans ){
      int nTrans = strlen30(zTrans)+1;
      if( nTrans>nLine ){
        zLine = realloc(zLine, nTrans);
        if( zLine==0 ){
          sqlite3_free(zTrans);
          return 0;

    zResult = shell_readline(zPrompt);
    if( zResult && *zResult ) shell_add_history(zResult);
#endif
  }
  return zResult;
}

#if defined(SQLITE_ENABLE_SESSION)
/*

** State information for a single open session

*/


typedef struct OpenSession OpenSession;
struct OpenSession {



  char *zName;             /* Symbolic name for this session */
  int nFilter;             /* Number of xFilter rejection GLOB patterns */
  char **azFilter;         /* Array of xFilter rejection GLOB patterns */
  sqlite3_session *p;      /* The open session */




};




#endif

/*








** Shell output mode information from before ".explain on",
** saved so that it can be restored by ".explain off"
*/
typedef struct SavedModeInfo SavedModeInfo;
struct SavedModeInfo {
  int valid;          /* Is there legit data in here? */
  int mode;           /* Mode prior to ".explain on" */
  int showHeader;     /* The ".header" setting prior to ".explain on" */

  char *zFreeOnClose;         /* Filename to free when closing */
  const char *zVfs;           /* Name of VFS to use */
  sqlite3_stmt *pStmt;   /* Current statement if any. */
  FILE *pLog;            /* Write log output here */
  int *aiIndent;         /* Array of indents used in MODE_Explain */
  int nIndent;           /* Size of array aiIndent[] */
  int iIndent;           /* Index of current op in aiIndent[] */
#if defined(SQLITE_ENABLE_SESSION)
  int nSession;             /* Number of active sessions */
  OpenSession aSession[4];  /* Array of sessions.  [0] is in focus. */
#endif
};

/*
** These are the allowed shellFlgs values
*/
#define SHFLG_Scratch     0x00001     /* The --scratch option is used */
#define SHFLG_Pagecache   0x00002     /* The --pagecache option is used */

/*
** Output the given string as a quoted string using SQL quoting conventions.
*/
static void output_quoted_string(FILE *out, const char *z){
  int i;
  int nSingle = 0;
  setBinaryMode(out, 1);
  for(i=0; z[i]; i++){
    if( z[i]=='\'' ) nSingle++;
  }
  if( nSingle==0 ){
    utf8_printf(out,"'%s'",z);
  }else{
    raw_printf(out,"'");

      }else{
        utf8_printf(out,"%s",z);
        break;
      }
    }
    raw_printf(out,"'");
  }
  setTextMode(out, 1);
}

/*
** Output the given string as a quoted according to C or TCL quoting rules.
*/
static void output_c_string(FILE *out, const char *z){
  unsigned int c;

** Output the given string with characters that are special to
** HTML escaped.
*/
static void output_html_string(FILE *out, const char *z){
  int i;
  if( z==0 ) z = "";
  while( *z ){
    for(i=0;   z[i]
            && z[i]!='<'
            && z[i]!='&'
            && z[i]!='>'
            && z[i]!='\"'
            && z[i]!='\'';
        i++){}
    if( i>0 ){
      utf8_printf(out,"%.*s",i,z);
    }
    if( z[i]=='<' ){
      raw_printf(out,"&lt;");

}

/*
** If a field contains any character identified by a 1 in the following
** array, then the string must be quoted for CSV.
*/
static const char needCsvQuote[] = {
  1, 1, 1, 1, 1, 1, 1, 1,   1, 1, 1, 1, 1, 1, 1, 1,
  1, 1, 1, 1, 1, 1, 1, 1,   1, 1, 1, 1, 1, 1, 1, 1,
  1, 0, 1, 0, 0, 0, 0, 1,   0, 0, 0, 0, 0, 0, 0, 0,
  0, 0, 0, 0, 0, 0, 0, 0,   0, 0, 0, 0, 0, 0, 0, 0,
  0, 0, 0, 0, 0, 0, 0, 0,   0, 0, 0, 0, 0, 0, 0, 0,
  0, 0, 0, 0, 0, 0, 0, 0,   0, 0, 0, 0, 0, 0, 0, 0,
  0, 0, 0, 0, 0, 0, 0, 0,   0, 0, 0, 0, 0, 0, 0, 0,
  0, 0, 0, 0, 0, 0, 0, 0,   0, 0, 0, 0, 0, 0, 0, 1,
  1, 1, 1, 1, 1, 1, 1, 1,   1, 1, 1, 1, 1, 1, 1, 1,
  1, 1, 1, 1, 1, 1, 1, 1,   1, 1, 1, 1, 1, 1, 1, 1,
  1, 1, 1, 1, 1, 1, 1, 1,   1, 1, 1, 1, 1, 1, 1, 1,
  1, 1, 1, 1, 1, 1, 1, 1,   1, 1, 1, 1, 1, 1, 1, 1,
  1, 1, 1, 1, 1, 1, 1, 1,   1, 1, 1, 1, 1, 1, 1, 1,
  1, 1, 1, 1, 1, 1, 1, 1,   1, 1, 1, 1, 1, 1, 1, 1,
  1, 1, 1, 1, 1, 1, 1, 1,   1, 1, 1, 1, 1, 1, 1, 1,
  1, 1, 1, 1, 1, 1, 1, 1,   1, 1, 1, 1, 1, 1, 1, 1,
};

/*
** Output a single term of CSV.  Actually, p->colSeparator is used for
** the separator, which may or may not be a comma.  p->nullValue is
** the null value.  Strings are quoted if necessary.  The separator
** is only issued if bSep is true.
*/
static void output_csv(ShellState *p, const char *z, int bSep){
  FILE *out = p->out;
  if( z==0 ){
    utf8_printf(out,"%s",p->nullValue);
  }else{
    int i;
    int nSep = strlen30(p->colSeparator);
    for(i=0; z[i]; i++){
      if( needCsvQuote[((unsigned char*)z)[i]]
         || (z[i]==p->colSeparator[0] &&
             (nSep==1 || memcmp(z, p->colSeparator, nSep)==0)) ){
        i = 0;
        break;
      }
    }
    if( i==0 ){
      putc('"', out);

static void interrupt_handler(int NotUsed){
  UNUSED_PARAMETER(NotUsed);
  seenInterrupt++;
  if( seenInterrupt>2 ) exit(1);
  if( globalDb ) sqlite3_interrupt(globalDb);
}
#endif

/*
** When the ".auth ON" is set, the following authorizer callback is
** invoked.  It always returns SQLITE_OK.
*/
static int shellAuth(
  void *pClientData,
  int op,
  const char *zA1,
  const char *zA2,
  const char *zA3,
  const char *zA4
){
  ShellState *p = (ShellState*)pClientData;
  static const char *azAction[] = { 0,
     "CREATE_INDEX",         "CREATE_TABLE",         "CREATE_TEMP_INDEX",
     "CREATE_TEMP_TABLE",    "CREATE_TEMP_TRIGGER",  "CREATE_TEMP_VIEW",
     "CREATE_TRIGGER",       "CREATE_VIEW",          "DELETE",
     "DROP_INDEX",           "DROP_TABLE",           "DROP_TEMP_INDEX",
     "DROP_TEMP_TABLE",      "DROP_TEMP_TRIGGER",    "DROP_TEMP_VIEW",
     "DROP_TRIGGER",         "DROP_VIEW",            "INSERT",
     "PRAGMA",               "READ",                 "SELECT",
     "TRANSACTION",          "UPDATE",               "ATTACH",
     "DETACH",               "ALTER_TABLE",          "REINDEX",
     "ANALYZE",              "CREATE_VTABLE",        "DROP_VTABLE",
     "FUNCTION",             "SAVEPOINT",            "RECURSIVE"
  };
  int i;
  const char *az[4];
  az[0] = zA1;
  az[1] = zA2;
  az[2] = zA3;
  az[3] = zA4;
  raw_printf(p->out, "authorizer: %s", azAction[op]);
  for(i=0; i<4; i++){
    raw_printf(p->out, " ");
    if( az[i] ){
      output_c_string(p->out, az[i]);
    }else{
      raw_printf(p->out, "NULL");
    }
  }
  raw_printf(p->out, "\n");
  return SQLITE_OK;
}
  

/*
** This is the callback routine that the shell
** invokes for each row of a query result.
*/
static int shell_callback(
  void *pArg,

        output_c_string(p->out, azArg[i] ? azArg[i] : p->nullValue);
        if(i<nArg-1) utf8_printf(p->out, "%s", p->colSeparator);
      }
      utf8_printf(p->out, "%s", p->rowSeparator);
      break;
    }
    case MODE_Csv: {
      setBinaryMode(p->out, 1);
      if( p->cnt++==0 && p->showHeader ){
        for(i=0; i<nArg; i++){
          output_csv(p, azCol[i] ? azCol[i] : "", i<nArg-1);
        }
        utf8_printf(p->out, "%s", p->rowSeparator);
      }
      if( nArg>0 ){
        for(i=0; i<nArg; i++){
          output_csv(p, azArg[i], i<nArg-1);
        }
        utf8_printf(p->out, "%s", p->rowSeparator);
      }
      setTextMode(p->out, 1);
      break;
    }
    case MODE_Insert: {
      p->cnt++;
      if( azArg==0 ) break;
      utf8_printf(p->out,"INSERT INTO %s",p->zDestTable);
      if( p->showHeader ){

}

/* zIn is either a pointer to a NULL-terminated string in memory obtained
** from malloc(), or a NULL pointer. The string pointed to by zAppend is
** added to zIn, and the result returned in memory obtained from malloc().
** zIn, if it was not NULL, is freed.
**
** If the third argument, quote, is not '\0', then it is used as a
** quote character for zAppend.
*/
static char *appendText(char *zIn, char const *zAppend, char quote){
  int len;
  int i;
  int nAppend = strlen30(zAppend);
  int nIn = (zIn?strlen30(zIn):0);

/*
** Execute a query statement that will generate SQL output.  Print
** the result columns, comma-separated, on a line and then add a
** semicolon terminator to the end of that line.
**
** If the number of columns is 1 and that column contains text "--"
** then write the semicolon on a separate line.  That way, if a
** "--" comment occurs at the end of the statement, the comment
** won't consume the semicolon terminator.
*/
static int run_table_dump_query(
  ShellState *p,           /* Query context */
  const char *zSelect,     /* SELECT statement to extract content */
  const char *zFirstRow    /* Print before first row, if not NULL */

  while( rc==SQLITE_ROW ){
    if( zFirstRow ){
      utf8_printf(p->out, "%s", zFirstRow);
      zFirstRow = 0;
    }
    z = (const char*)sqlite3_column_text(pSelect, 0);
    utf8_printf(p->out, "%s", z);
    for(i=1; i<nResult; i++){
      utf8_printf(p->out, ",%s", sqlite3_column_text(pSelect, i));
    }
    if( z==0 ) z = "";
    while( z[0] && (z[0]!='-' || z[1]!='-') ) z++;
    if( z[0] ){
      raw_printf(p->out, "\n;\n");
    }else{
      raw_printf(p->out, ";\n");
    }
    rc = sqlite3_step(pSelect);
  }
  rc = sqlite3_finalize(pSelect);
  if( rc!=SQLITE_OK ){
    utf8_printf(p->out, "/**** ERROR: (%d) %s *****/\n", rc,
                sqlite3_errmsg(p->db));
    if( (rc&0xff)!=SQLITE_CORRUPT ) p->nErr++;

      if( strncmp(aTrans[i].zPattern, z, n)==0 ){
        raw_printf(out, "%-36s %s", aTrans[i].zDesc, &z[n]);
        break;
      }
    }
  }
  fclose(in);
}
#endif


/*
** Display memory stats.
*/
static int display_stats(
  sqlite3 *db,                /* Database to query */
  ShellState *pArg,           /* Pointer to ShellState */
  int bReset                  /* True to reset the stats */
){
  int iCur;
  int iHiwtr;

  if( pArg && pArg->out ){

    iHiwtr = iCur = -1;
    sqlite3_status(SQLITE_STATUS_MEMORY_USED, &iCur, &iHiwtr, bReset);
    raw_printf(pArg->out,
            "Memory Used:                         %d (max %d) bytes\n",
            iCur, iHiwtr);
    iHiwtr = iCur = -1;
    sqlite3_status(SQLITE_STATUS_MALLOC_COUNT, &iCur, &iHiwtr, bReset);

    raw_printf(pArg->out, "Pager Heap Usage:                    %d bytes\n",
            iCur);
    iHiwtr = iCur = -1;
    sqlite3_db_status(db, SQLITE_DBSTATUS_CACHE_HIT, &iCur, &iHiwtr, 1);
    raw_printf(pArg->out, "Page cache hits:                     %d\n", iCur);
    iHiwtr = iCur = -1;
    sqlite3_db_status(db, SQLITE_DBSTATUS_CACHE_MISS, &iCur, &iHiwtr, 1);
    raw_printf(pArg->out, "Page cache misses:                   %d\n", iCur);
    iHiwtr = iCur = -1;
    sqlite3_db_status(db, SQLITE_DBSTATUS_CACHE_WRITE, &iCur, &iHiwtr, 1);
    raw_printf(pArg->out, "Page cache writes:                   %d\n", iCur);
    iHiwtr = iCur = -1;
    sqlite3_db_status(db, SQLITE_DBSTATUS_SCHEMA_USED, &iCur, &iHiwtr, bReset);
    raw_printf(pArg->out, "Schema Heap Usage:                   %d bytes\n",
            iCur);
    iHiwtr = iCur = -1;
    sqlite3_db_status(db, SQLITE_DBSTATUS_STMT_USED, &iCur, &iHiwtr, bReset);
    raw_printf(pArg->out, "Statement Heap/Lookaside Usage:      %d bytes\n",
            iCur);
  }

  if( pArg && pArg->out && db && pArg->pStmt ){
    iCur = sqlite3_stmt_status(pArg->pStmt, SQLITE_STMTSTATUS_FULLSCAN_STEP,
                               bReset);
    raw_printf(pArg->out, "Fullscan Steps:                      %d\n", iCur);
    iCur = sqlite3_stmt_status(pArg->pStmt, SQLITE_STMTSTATUS_SORT, bReset);

      }
      n++;
      sqlite3_stmt_scanstatus(p, i, SQLITE_SCANSTAT_NVISIT, (void*)&nVisit);
      sqlite3_stmt_scanstatus(p, i, SQLITE_SCANSTAT_EST, (void*)&rEst);
      sqlite3_stmt_scanstatus(p, i, SQLITE_SCANSTAT_EXPLAIN, (void*)&zExplain);
      utf8_printf(pArg->out, "Loop %2d: %s\n", n, zExplain);
      rEstLoop *= rEst;
      raw_printf(pArg->out,
          "         nLoop=%-8lld nRow=%-8lld estRow=%-8lld estRow/Loop=%-8g\n",
          nLoop, nVisit, (sqlite3_int64)(rEstLoop+0.5), rEst
      );
    }
  }
  raw_printf(pArg->out, "---------------------------\n");
#endif

  }
  return 0;
}

/*
** If compiled statement pSql appears to be an EXPLAIN statement, allocate
** and populate the ShellState.aiIndent[] array with the number of
** spaces each opcode should be indented before it is output.
**
** The indenting rules are:
**
**     * For each "Next", "Prev", "VNext" or "VPrev" instruction, indent
**       all opcodes that occur between the p2 jump destination and the opcode
**       itself by 2 spaces.
**

  sqlite3_free(p->aiIndent);
  p->aiIndent = 0;
  p->nIndent = 0;
  p->iIndent = 0;
}

/*
** Execute a statement or set of statements.  Print
** any result rows/columns depending on the current mode
** set via the supplied callback.
**
** This is very similar to SQLite's built-in sqlite3_exec()
** function except it takes a slightly different callback
** and callback data argument.
*/
static int shell_exec(
  sqlite3 *db,                              /* An open database */
  const char *zSql,                         /* SQL to be evaluated */
  int (*xCallback)(void*,int,char**,char**,int*),   /* Callback function */
                                            /* (not the same as sqlite3_exec) */

        pArg->cMode = pArg->mode;
        if( pArg->autoExplain
         && sqlite3_column_count(pStmt)==8
         && sqlite3_strlike("%EXPLAIN%", sqlite3_sql(pStmt),0)==0
        ){
          pArg->cMode = MODE_Explain;
        }

        /* If the shell is currently in ".explain" mode, gather the extra
        ** data required to add indents to the output.*/
        if( pArg->cMode==MODE_Explain ){
          explain_data_prepare(pArg, pStmt);
        }
      }

          if( !pData ){
            rc = SQLITE_NOMEM;
          }else{
            char **azCols = (char **)pData;      /* Names of result columns */
            char **azVals = &azCols[nCol];       /* Results */
            int *aiTypes = (int *)&azVals[nCol]; /* Result types */
            int i, x;
            assert(sizeof(int) <= sizeof(char *));
            /* save off ptrs to column names */
            for(i=0; i<nCol; i++){
              azCols[i] = (char *)sqlite3_column_name(pStmt, i);
            }
            do{
              /* extract the data and data types */
              for(i=0; i<nCol; i++){
                aiTypes[i] = x = sqlite3_column_type(pStmt, i);
                if( x==SQLITE_BLOB && pArg && pArg->cMode==MODE_Insert ){
                  azVals[i] = "";
                }else{
                  azVals[i] = (char*)sqlite3_column_text(pStmt, i);
                }
                if( !azVals[i] && (aiTypes[i]!=SQLITE_NULL) ){
                  rc = SQLITE_NOMEM;
                  break; /* from for */
                }
              } /* end for */

              /* if data and types extracted successfully... */
              if( SQLITE_ROW == rc ){
                /* call the supplied callback with the result row data */
                if( xCallback(pArg, nCol, azVals, azCols, aiTypes) ){
                  rc = SQLITE_ABORT;
                }else{
                  rc = sqlite3_step(pStmt);
                }
              }

      }

      /* print loop-counters if required */
      if( pArg && pArg->scanstatsOn ){
        display_scanstats(db, pArg);
      }

      /* Finalize the statement just executed. If this fails, save a
      ** copy of the error message. Otherwise, set zSql to point to the
      ** next statement to execute. */
      rc2 = sqlite3_finalize(pStmt);
      if( rc!=SQLITE_NOMEM ) rc = rc2;
      if( rc==SQLITE_OK ){
        zSql = zLeftover;
        while( IsSpace(zSql[0]) ) zSql++;

  ShellState *p = (ShellState *)pArg;

  UNUSED_PARAMETER(azCol);
  if( nArg!=3 ) return 1;
  zTable = azArg[0];
  zType = azArg[1];
  zSql = azArg[2];

  if( strcmp(zTable, "sqlite_sequence")==0 ){
    zPrepStmt = "DELETE FROM sqlite_sequence;\n";
  }else if( sqlite3_strglob("sqlite_stat?", zTable)==0 ){
    raw_printf(p->out, "ANALYZE sqlite_master;\n");
  }else if( strncmp(zTable, "sqlite_", 7)==0 ){
    return 0;
  }else if( strncmp(zSql, "CREATE VIRTUAL TABLE", 20)==0 ){

  if( strcmp(zType, "table")==0 ){
    sqlite3_stmt *pTableInfo = 0;
    char *zSelect = 0;
    char *zTableInfo = 0;
    char *zTmp = 0;
    int nRow = 0;

    zTableInfo = appendText(zTableInfo, "PRAGMA table_info(", 0);
    zTableInfo = appendText(zTableInfo, zTable, '"');
    zTableInfo = appendText(zTableInfo, ");", 0);

    rc = sqlite3_prepare_v2(p->db, zTableInfo, -1, &pTableInfo, 0);
    free(zTableInfo);
    if( rc!=SQLITE_OK || !pTableInfo ){

** Run zQuery.  Use dump_callback() as the callback routine so that
** the contents of the query are output as SQL statements.
**
** If we get a SQLITE_CORRUPT error, rerun the query after appending
** "ORDER BY rowid DESC" to the end.
*/
static int run_schema_dump_query(
  ShellState *p,
  const char *zQuery
){
  int rc;
  char *zErr = 0;
  rc = sqlite3_exec(p->db, zQuery, dump_callback, p, &zErr);
  if( rc==SQLITE_CORRUPT ){
    char *zQ2;

  return rc;
}

/*
** Text of a help message
*/
static char zHelp[] =
  ".auth ON|OFF           Show authorizer callbacks\n"
  ".backup ?DB? FILE      Backup DB (default \"main\") to FILE\n"
  ".bail on|off           Stop after hitting an error.  Default OFF\n"
  ".binary on|off         Turn binary output on or off.  Default OFF\n"
  ".changes on|off        Show number of rows changed by SQL\n"
  ".clone NEWDB           Clone data into NEWDB from the existing database\n"
  ".databases             List names and files of attached databases\n"
  ".dbinfo ?DB?           Show status information about the database\n"

  ".save FILE             Write in-memory database into FILE\n"
  ".scanstats on|off      Turn sqlite3_stmt_scanstatus() metrics on or off\n"
  ".schema ?TABLE?        Show the CREATE statements\n"
  "                         If TABLE specified, only show tables matching\n"
  "                         LIKE pattern TABLE.\n"
  ".separator COL ?ROW?   Change the column separator and optionally the row\n"
  "                         separator for both the output mode and .import\n"
#if defined(SQLITE_ENABLE_SESSION)
  ".session CMD ...       Create or control sessions\n"
#endif
  ".shell CMD ARGS...     Run CMD ARGS... in a system shell\n"
  ".show                  Show the current values for various settings\n"
  ".stats ?on|off?        Show stats or turn stats on or off\n"
  ".system CMD ARGS...    Run CMD ARGS... in a system shell\n"
  ".tables ?TABLE?        List names of tables\n"
  "                         If TABLE specified, only list tables matching\n"
  "                         LIKE pattern TABLE.\n"
  ".timeout MS            Try opening locked tables for MS milliseconds\n"
  ".timer on|off          Turn SQL timer on or off\n"
  ".trace FILE|off        Output each SQL statement as it is run\n"
  ".vfsinfo ?AUX?         Information about the top-level VFS\n"
  ".vfslist               List all available VFSes\n"
  ".vfsname ?AUX?         Print the name of the VFS stack\n"
  ".width NUM1 NUM2 ...   Set column widths for \"column\" mode\n"
  "                         Negative values right-justify\n"
;

#if defined(SQLITE_ENABLE_SESSION)
/*
** Print help information for the ".sessions" command
*/
void session_help(ShellState *p){
  raw_printf(p->out,
    ".session ?NAME? SUBCOMMAND ?ARGS...?\n"
    "If ?NAME? is omitted, the first defined session is used.\n"
    "Subcommands:\n"
    "   attach TABLE             Attach TABLE\n"
    "   changeset FILE           Write a changeset into FILE\n"
    "   close                    Close one session\n"
    "   enable ?BOOLEAN?         Set or query the enable bit\n"
    "   filter GLOB...           Reject tables matching GLOBs\n"
    "   indirect ?BOOLEAN?       Mark or query the indirect status\n"
    "   isempty                  Query whether the session is empty\n"
    "   list                     List currently open session names\n"
    "   open DB NAME             Open a new session on DB\n"
    "   patchset FILE            Write a patchset into FILE\n"
  );
}
#endif


/* Forward reference */
static int process_input(ShellState *p, FILE *in);
/*
** Implementation of the "readfile(X)" SQL function.  The entire content
** of the file named X is read and returned as a BLOB.  NULL is returned
** if the file does not exist or is unreadable.

  }else{
    rc = fwrite(z, 1, sqlite3_value_bytes(argv[1]), out);
  }
  fclose(out);
  sqlite3_result_int64(context, rc);
}

#if defined(SQLITE_ENABLE_SESSION)
/*
** Close a single OpenSession object and release all of its associated
** resources.
*/
static void session_close(OpenSession *pSession){
  int i;
  sqlite3session_delete(pSession->p);
  sqlite3_free(pSession->zName);
  for(i=0; i<pSession->nFilter; i++){
    sqlite3_free(pSession->azFilter[i]);
  }
  sqlite3_free(pSession->azFilter);
  memset(pSession, 0, sizeof(OpenSession));
}
#endif

/*
** Close all OpenSession objects and release all associated resources.
*/
#if defined(SQLITE_ENABLE_SESSION)
static void session_close_all(ShellState *p){
  int i;
  for(i=0; i<p->nSession; i++){
    session_close(&p->aSession[i]);
  }
  p->nSession = 0;
}
#else
# define session_close_all(X)
#endif

/*
** Implementation of the xFilter function for an open session.  Omit
** any tables named by ".session filter" but let all other table through.
*/
#if defined(SQLITE_ENABLE_SESSION)
static int session_filter(void *pCtx, const char *zTab){
  OpenSession *pSession = (OpenSession*)pCtx;
  int i;
  for(i=0; i<pSession->nFilter; i++){
    if( sqlite3_strglob(pSession->azFilter[i], zTab)==0 ) return 0;
  }
  return 1;
}
#endif

/*
** Make sure the database is open.  If it is not, then open it.  If
** the database fails to open, print an error message and exit.
*/
static void open_db(ShellState *p, int keepAlive){
  if( p->db==0 ){
    sqlite3_initialize();
    sqlite3_open(p->zDbFilename, &p->db);
    globalDb = p->db;
    if( p->db && sqlite3_errcode(p->db)==SQLITE_OK ){
      sqlite3_create_function(p->db, "shellstatic", 0, SQLITE_UTF8, 0,
          shellstaticFunc, 0, 0);
    }
    if( p->db==0 || SQLITE_OK!=sqlite3_errcode(p->db) ){
      utf8_printf(stderr,"Error: unable to open database \"%s\": %s\n",
          p->zDbFilename, sqlite3_errmsg(p->db));
      if( keepAlive ) return;
      exit(1);
    }
#ifndef SQLITE_OMIT_LOAD_EXTENSION
    sqlite3_enable_load_extension(p->db, 1);
#endif

*/
static void output_file_close(FILE *f){
  if( f && f!=stdout && f!=stderr ) fclose(f);
}

/*
** Try to open an output file.   The names "stdout" and "stderr" are
** recognized and do the right thing.  NULL is returned if the output
** filename is "off".
*/
static FILE *output_file_open(const char *zFile){
  FILE *f;
  if( strcmp(zFile,"stdout")==0 ){
    f = stdout;
  }else if( strcmp(zFile, "stderr")==0 ){

** work for WITHOUT ROWID tables.
*/
static void tryToCloneData(
  ShellState *p,
  sqlite3 *newDb,
  const char *zTable
){
  sqlite3_stmt *pQuery = 0;
  sqlite3_stmt *pInsert = 0;
  char *zQuery = 0;
  char *zInsert = 0;
  int rc;
  int i, j, n;
  int nTable = (int)strlen(zTable);
  int k = 0;

  utf8_printf(p->out, "%-20s %d\n", "reserved bytes:", aHdr[20]);
  for(i=0; i<ArraySize(aField); i++){
    int ofst = aField[i].ofst;
    unsigned int val = get4byteInt(aHdr + ofst);
    utf8_printf(p->out, "%-20s %u", aField[i].zName, val);
    switch( ofst ){
      case 56: {
        if( val==1 ) raw_printf(p->out, " (utf8)");
        if( val==2 ) raw_printf(p->out, " (utf16le)");
        if( val==3 ) raw_printf(p->out, " (utf16be)");
      }
    }
    raw_printf(p->out, "\n");
  }
  if( zDb==0 ){
    zSchemaTab = sqlite3_mprintf("main.sqlite_master");
  }else if( strcmp(zDb,"temp")==0 ){

  */
  while( zLine[h] && nArg<ArraySize(azArg) ){
    while( IsSpace(zLine[h]) ){ h++; }
    if( zLine[h]==0 ) break;
    if( zLine[h]=='\'' || zLine[h]=='"' ){
      int delim = zLine[h++];
      azArg[nArg++] = &zLine[h];
      while( zLine[h] && zLine[h]!=delim ){
        if( zLine[h]=='\\' && delim=='"' && zLine[h+1]!=0 ) h++;
        h++;
      }
      if( zLine[h]==delim ){
        zLine[h++] = 0;
      }
      if( delim=='"' ) resolve_backslashes(azArg[nArg-1]);
    }else{
      azArg[nArg++] = &zLine[h];
      while( zLine[h] && !IsSpace(zLine[h]) ){ h++; }
      if( zLine[h] ) zLine[h++] = 0;
      resolve_backslashes(azArg[nArg-1]);
    }
  }

  /* Process the input line.
  */
  if( nArg==0 ) return 0; /* no tokens, no error */
  n = strlen30(azArg[0]);
  c = azArg[0][0];

  if( c=='a' && strncmp(azArg[0], "auth", n)==0 ){
    if( nArg!=2 ){
      raw_printf(stderr, "Usage: .auth ON|OFF\n");
      rc = 1;
      goto meta_command_exit;
    }
    open_db(p, 0);
    if( booleanValue(azArg[1]) ){
      sqlite3_set_authorizer(p->db, shellAuth, p);
    }else{
      sqlite3_set_authorizer(p->db, 0, 0);
    }
  }else

  if( (c=='b' && n>=3 && strncmp(azArg[0], "backup", n)==0)
   || (c=='s' && n>=3 && strncmp(azArg[0], "save", n)==0)
  ){
    const char *zDestFile = 0;
    const char *zDb = 0;
    sqlite3 *pDest;
    sqlite3_backup *pBackup;

      rc = 1;
    }
  }else

  if( c=='b' && n>=3 && strncmp(azArg[0], "binary", n)==0 ){
    if( nArg==2 ){
      if( booleanValue(azArg[1]) ){
        setBinaryMode(p->out, 1);
      }else{
        setTextMode(p->out, 1);
      }
    }else{
      raw_printf(stderr, "Usage: .binary on|off\n");
      rc = 1;
    }
  }else

    }
    raw_printf(p->out, "PRAGMA foreign_keys=OFF;\n");
    raw_printf(p->out, "BEGIN TRANSACTION;\n");
    p->writableSchema = 0;
    sqlite3_exec(p->db, "SAVEPOINT dump; PRAGMA writable_schema=ON", 0, 0, 0);
    p->nErr = 0;
    if( nArg==1 ){
      run_schema_dump_query(p,
        "SELECT name, type, sql FROM sqlite_master "
        "WHERE sql NOT NULL AND type=='table' AND name!='sqlite_sequence'"
      );
      run_schema_dump_query(p,
        "SELECT name, type, sql FROM sqlite_master "
        "WHERE name=='sqlite_sequence'"
      );
      run_table_dump_query(p,
        "SELECT sql FROM sqlite_master "
        "WHERE sql NOT NULL AND type IN ('index','trigger','view')", 0
      );

  if( c=='e' && strncmp(azArg[0], "eqp", n)==0 ){
    if( nArg==2 ){
      p->autoEQP = booleanValue(azArg[1]);
    }else{
      raw_printf(stderr, "Usage: .eqp on|off\n");
      rc = 1;
    }
  }else

  if( c=='e' && strncmp(azArg[0], "exit", n)==0 ){
    if( nArg>1 && (rc = (int)integerValue(azArg[1]))!=0 ) exit(rc);
    rc = 2;
  }else

      { "trigger_depth",         SQLITE_LIMIT_TRIGGER_DEPTH             },
      { "worker_threads",        SQLITE_LIMIT_WORKER_THREADS            },
    };
    int i, n2;
    open_db(p, 0);
    if( nArg==1 ){
      for(i=0; i<ArraySize(aLimit); i++){
        printf("%20s %d\n", aLimit[i].zLimitName,
               sqlite3_limit(p->db, aLimit[i].limitCode, -1));
      }
    }else if( nArg>3 ){
      raw_printf(stderr, "Usage: .limit NAME ?NEW-VALUE?\n");
      rc = 1;
      goto meta_command_exit;
    }else{

    const char *zSavedFilename = p->zDbFilename;
    char *zNewFilename = 0;
    p->db = 0;
    if( nArg>=2 ) zNewFilename = sqlite3_mprintf("%s", azArg[1]);
    p->zDbFilename = zNewFilename;
    open_db(p, 1);
    if( p->db!=0 ){
      session_close_all(p);
      sqlite3_close(savedDb);
      sqlite3_free(p->zFreeOnClose);
      p->zFreeOnClose = zNewFilename;
    }else{
      sqlite3_free(zNewFilename);
      p->db = savedDb;
      p->zDbFilename = zSavedFilename;

      raw_printf(stderr,"Error: querying schema information\n");
      rc = 1;
    }else{
      rc = 0;
    }
  }else


#if defined(SQLITE_DEBUG) && defined(SQLITE_ENABLE_SELECTTRACE)
  if( c=='s' && n==11 && strncmp(azArg[0], "selecttrace", n)==0 ){
    extern int sqlite3SelectTrace;
    sqlite3SelectTrace = integerValue(azArg[1]);
  }else
#endif

#if defined(SQLITE_ENABLE_SESSION)
  if( c=='s' && strncmp(azArg[0],"session",n)==0 && n>=3 ){
    OpenSession *pSession = &p->aSession[0];
    char **azCmd = &azArg[1];
    int iSes = 0;
    int nCmd = nArg - 1;
    int i;
    if( nArg<=1 ) goto session_syntax_error;
    open_db(p, 0);
    if( nArg>=3 ){
      for(iSes=0; iSes<p->nSession; iSes++){
        if( strcmp(p->aSession[iSes].zName, azArg[1])==0 ) break;
      }
      if( iSes<p->nSession ){
        pSession = &p->aSession[iSes];
        azCmd++;
        nCmd--;
      }else{
        pSession = &p->aSession[0];
        iSes = 0;
      }
    }

    /* .session attach TABLE
    ** Invoke the sqlite3session_attach() interface to attach a particular
    ** table so that it is never filtered.
    */
    if( strcmp(azCmd[0],"attach")==0 ){
      if( nCmd!=2 ) goto session_syntax_error;
      if( pSession->p==0 ){
        session_not_open:
        raw_printf(stderr, "ERROR: No sessions are open\n");
      }else{
        rc = sqlite3session_attach(pSession->p, azCmd[1]);
        if( rc ){
          raw_printf(stderr, "ERROR: sqlite3session_attach() returns %d\n", rc);
          rc = 0;
        }
      }
    }else

    /* .session changeset FILE
    ** .session patchset FILE
    ** Write a changeset or patchset into a file.  The file is overwritten.
    */
    if( strcmp(azCmd[0],"changeset")==0 || strcmp(azCmd[0],"patchset")==0 ){
      FILE *out = 0;
      if( nCmd!=2 ) goto session_syntax_error;
      if( pSession->p==0 ) goto session_not_open;
      out = fopen(azCmd[1], "wb");
      if( out==0 ){
        utf8_printf(stderr, "ERROR: cannot open \"%s\" for writing\n", azCmd[1]);
      }else{
        int szChng;
        void *pChng;
        if( azCmd[0][0]=='c' ){
          rc = sqlite3session_changeset(pSession->p, &szChng, &pChng);
        }else{
          rc = sqlite3session_patchset(pSession->p, &szChng, &pChng);
        }
        if( rc ){
          printf("Error: error code %d\n", rc);
          rc = 0;
        }
        if( pChng
          && fwrite(pChng, szChng, 1, out)!=1 ){
          raw_printf(stderr, "ERROR: Failed to write entire %d-byte output\n",
                  szChng);
        }
        sqlite3_free(pChng);
        fclose(out);
      }
    }else

    /* .session close
    ** Close the identified session
    */
    if( strcmp(azCmd[0], "close")==0 ){
      if( nCmd!=1 ) goto session_syntax_error;
      if( p->nSession ){
        session_close(pSession);
        p->aSession[iSes] = p->aSession[--p->nSession];
      }
    }else

    /* .session enable ?BOOLEAN?
    ** Query or set the enable flag
    */
    if( strcmp(azCmd[0], "enable")==0 ){
      int ii;
      if( nCmd>2 ) goto session_syntax_error;
      ii = nCmd==1 ? -1 : booleanValue(azCmd[1]);
      if( p->nSession ){
        ii = sqlite3session_enable(pSession->p, ii);
        utf8_printf(p->out, "session %s enable flag = %d\n",
                    pSession->zName, ii);
      }
    }else

    /* .session filter GLOB ....
    ** Set a list of GLOB patterns of table names to be excluded.
    */
    if( strcmp(azCmd[0], "filter")==0 ){
      int ii, nByte;
      if( nCmd<2 ) goto session_syntax_error;
      if( p->nSession ){
        for(ii=0; ii<pSession->nFilter; ii++){
          sqlite3_free(pSession->azFilter[ii]);
        }
        sqlite3_free(pSession->azFilter);
        nByte = sizeof(pSession->azFilter[0])*(nCmd-1);
        pSession->azFilter = sqlite3_malloc( nByte );
        if( pSession->azFilter==0 ){
          raw_printf(stderr, "Error: out or memory\n");
          exit(1);
        }
        for(ii=1; ii<nCmd; ii++){
          pSession->azFilter[ii-1] = sqlite3_mprintf("%s", azCmd[ii]);
        }
        pSession->nFilter = ii-1;
      }
    }else

    /* .session indirect ?BOOLEAN?
    ** Query or set the indirect flag
    */
    if( strcmp(azCmd[0], "indirect")==0 ){
      int ii;
      if( nCmd>2 ) goto session_syntax_error;
      ii = nCmd==1 ? -1 : booleanValue(azCmd[1]);
      if( p->nSession ){
        ii = sqlite3session_indirect(pSession->p, ii);
        utf8_printf(p->out, "session %s indirect flag = %d\n",
                    pSession->zName, ii);
      }
    }else

    /* .session isempty
    ** Determine if the session is empty
    */
    if( strcmp(azCmd[0], "isempty")==0 ){
      int ii;
      if( nCmd!=1 ) goto session_syntax_error;
      if( p->nSession ){
        ii = sqlite3session_isempty(pSession->p);
        utf8_printf(p->out, "session %s isempty flag = %d\n",
                    pSession->zName, ii);
      }
    }else

    /* .session list
    ** List all currently open sessions
    */
    if( strcmp(azCmd[0],"list")==0 ){
      for(i=0; i<p->nSession; i++){
        utf8_printf(p->out, "%d %s\n", i, p->aSession[i].zName);
      }
    }else

    /* .session open DB NAME
    ** Open a new session called NAME on the attached database DB.
    ** DB is normally "main".
    */
    if( strcmp(azCmd[0],"open")==0 ){
      char *zName;
      if( nCmd!=3 ) goto session_syntax_error;
      zName = azCmd[2];
      if( zName[0]==0 ) goto session_syntax_error;
      for(i=0; i<p->nSession; i++){
        if( strcmp(p->aSession[i].zName,zName)==0 ){
          utf8_printf(stderr, "Session \"%s\" already exists\n", zName);
          goto meta_command_exit;
        }
      }
      if( p->nSession>=ArraySize(p->aSession) ){
        raw_printf(stderr, "Maximum of %d sessions\n", ArraySize(p->aSession));
        goto meta_command_exit;
      }
      pSession = &p->aSession[p->nSession];
      rc = sqlite3session_create(p->db, azCmd[1], &pSession->p);
      if( rc ){
        raw_printf(stderr, "Cannot open session: error code=%d\n", rc);
        rc = 0;
        goto meta_command_exit;
      }
      pSession->nFilter = 0;
      sqlite3session_table_filter(pSession->p, session_filter, pSession);
      p->nSession++;
      pSession->zName = sqlite3_mprintf("%s", zName);
    }else
    /* If no command name matches, show a syntax error */
    session_syntax_error:
    session_help(p);
  }else
#endif

#ifdef SQLITE_DEBUG
  /* Undocumented commands for internal testing.  Subject to change
  ** without notice. */
  if( c=='s' && n>=10 && strncmp(azArg[0], "selftest-", 9)==0 ){
    if( strncmp(azArg[0]+9, "boolean", n-9)==0 ){
      int i, v;

    if( (testctrl<SQLITE_TESTCTRL_FIRST) || (testctrl>SQLITE_TESTCTRL_LAST) ){
      utf8_printf(stderr,"Error: invalid testctrl option: %s\n", azArg[1]);
    }else{
      switch(testctrl){

        /* sqlite3_test_control(int, db, int) */
        case SQLITE_TESTCTRL_OPTIMIZATIONS:
        case SQLITE_TESTCTRL_RESERVE:
          if( nArg==3 ){
            int opt = (int)strtol(azArg[2], 0, 0);
            rc2 = sqlite3_test_control(testctrl, p->db, opt);
            raw_printf(p->out, "%d (0x%08x)\n", rc2, rc2);
          } else {
            utf8_printf(stderr,"Error: testctrl %s takes a single int option\n",
                    azArg[1]);
          }
          break;

          } else {
            utf8_printf(stderr,"Error: testctrl %s takes no options\n",
                        azArg[1]);
          }
          break;

        /* sqlite3_test_control(int, uint) */
        case SQLITE_TESTCTRL_PENDING_BYTE:
          if( nArg==3 ){
            unsigned int opt = (unsigned int)integerValue(azArg[2]);
            rc2 = sqlite3_test_control(testctrl, opt);
            raw_printf(p->out, "%d (0x%08x)\n", rc2, rc2);
          } else {
            utf8_printf(stderr,"Error: testctrl %s takes a single unsigned"
                           " int option\n", azArg[1]);
          }
          break;

        /* sqlite3_test_control(int, int) */
        case SQLITE_TESTCTRL_ASSERT:
        case SQLITE_TESTCTRL_ALWAYS:
        case SQLITE_TESTCTRL_NEVER_CORRUPT:
          if( nArg==3 ){
            int opt = booleanValue(azArg[2]);
            rc2 = sqlite3_test_control(testctrl, opt);
            raw_printf(p->out, "%d (0x%08x)\n", rc2, rc2);
          } else {
            utf8_printf(stderr,"Error: testctrl %s takes a single int option\n",
                            azArg[1]);
          }
          break;

        /* sqlite3_test_control(int, char *) */
#ifdef SQLITE_N_KEYWORD
        case SQLITE_TESTCTRL_ISKEYWORD:
          if( nArg==3 ){
            const char *opt = azArg[2];
            rc2 = sqlite3_test_control(testctrl, opt);
            raw_printf(p->out, "%d (0x%08x)\n", rc2, rc2);
          } else {
            utf8_printf(stderr,
                        "Error: testctrl %s takes a single char * option\n",
                        azArg[1]);
          }
          break;
#endif

        case SQLITE_TESTCTRL_IMPOSTER:
          if( nArg==5 ){
            rc2 = sqlite3_test_control(testctrl, p->db,
                          azArg[2],
                          integerValue(azArg[3]),
                          integerValue(azArg[4]));
            raw_printf(p->out, "%d (0x%08x)\n", rc2, rc2);
          }else{
            raw_printf(stderr,"Usage: .testctrl imposter dbName onoff tnum\n");
          }
          break;

        case SQLITE_TESTCTRL_BITVEC_TEST:
        case SQLITE_TESTCTRL_FAULT_INSTALL:
        case SQLITE_TESTCTRL_BENIGN_MALLOC_HOOKS:
        case SQLITE_TESTCTRL_SCRATCHMALLOC:
        default:
          utf8_printf(stderr,
                      "Error: CLI support for testctrl %s not implemented\n",
                      azArg[1]);
          break;
      }
    }
  }else

  if( c=='t' && n>4 && strncmp(azArg[0], "timeout", n)==0 ){
    open_db(p, 0);
    sqlite3_busy_timeout(p->db, nArg>=2 ? (int)integerValue(azArg[1]) : 0);
  }else

  if( c=='t' && n>=5 && strncmp(azArg[0], "timer", n)==0 ){
    if( nArg==2 ){
      enableTimer = booleanValue(azArg[1]);
      if( enableTimer && !HAS_TIMER ){
        raw_printf(stderr, "Error: timer not available on this system.\n");
        enableTimer = 0;
      }
    }else{
      raw_printf(stderr, "Usage: .timer on|off\n");
      rc = 1;
    }
  }else

  if( c=='t' && strncmp(azArg[0], "trace", n)==0 ){
    open_db(p, 0);
    if( nArg!=2 ){
      raw_printf(stderr, "Usage: .trace FILE|off\n");
      rc = 1;
      goto meta_command_exit;
    }

        raw_printf(stderr, "User-Delete failed: %d\n", rc);
        rc = 1;
      }
    }else{
      raw_printf(stderr, "Usage: .user login|add|edit|delete ...\n");
      rc = 1;
      goto meta_command_exit;
    }
  }else
#endif /* SQLITE_USER_AUTHENTICATION */

  if( c=='v' && strncmp(azArg[0], "version", n)==0 ){
    utf8_printf(p->out, "SQLite %s %s\n" /*extra-version-info*/,
        sqlite3_libversion(), sqlite3_sourceid());
  }else

      if( p->backslashOn ) resolve_backslashes(zSql);
      BEGIN_TIMER;
      rc = shell_exec(p->db, zSql, shell_callback, p, &zErrMsg);
      END_TIMER;
      if( rc || zErrMsg ){
        char zPrefix[100];
        if( in!=0 || !stdin_is_interactive ){
          sqlite3_snprintf(sizeof(zPrefix), zPrefix,
                           "Error: near line %d:", startline);
        }else{
          sqlite3_snprintf(sizeof(zPrefix), zPrefix, "Error:");
        }
        if( zErrMsg!=0 ){
          utf8_printf(stderr, "%s %s\n", zPrefix, zErrMsg);
          sqlite3_free(zErrMsg);

  }
  sqlite3_free(zBuf);
}

/*
** Show available command line options
*/
static const char zOptions[] =
  "   -ascii               set output mode to 'ascii'\n"
  "   -bail                stop after hitting an error\n"
  "   -batch               force batch I/O\n"
  "   -column              set output mode to 'column'\n"
  "   -cmd COMMAND         run \"COMMAND\" before reading stdin\n"
  "   -csv                 set output mode to 'csv'\n"
  "   -echo                print commands before execution\n"

  "   -vfs NAME            use NAME as the default VFS\n"
#ifdef SQLITE_ENABLE_VFSTRACE
  "   -vfstrace            enable tracing of all VFS calls\n"
#endif
;
static void usage(int showDetail){
  utf8_printf(stderr,
      "Usage: %s [OPTIONS] FILENAME [SQL]\n"
      "FILENAME is the name of an SQLite database. A new database is created\n"
      "if the file does not previously exist.\n", Argv0);
  if( showDetail ){
    utf8_printf(stderr, "OPTIONS include:\n%s", zOptions);
  }else{
    raw_printf(stderr, "Use the -help option for additional information\n");
  }

    utf8_printf(stderr, "%s: Error: missing argument to %s\n",
            argv[0], argv[argc-1]);
    exit(1);
  }
  return argv[i];
}

#ifndef SQLITE_SHELL_IS_UTF8
#  if (defined(_WIN32) || defined(WIN32)) && defined(_MSC_VER)
#    define SQLITE_SHELL_IS_UTF8          (0)
#  else
#    define SQLITE_SHELL_IS_UTF8          (1)
#  endif
#endif

#if SQLITE_SHELL_IS_UTF8
int SQLITE_CDECL main(int argc, char **argv){
#else
int SQLITE_CDECL wmain(int argc, wchar_t **wargv){
  char **argv;
#endif
  char *zErrMsg = 0;
  ShellState data;
  const char *zInitFile = 0;
  int i;
  int rc = 0;
  int warnInmemoryDb = 0;
  int readStdin = 1;
  int nCmd = 0;
  char **azCmd = 0;

  setBinaryMode(stdin, 0);
  setvbuf(stderr, 0, _IONBF, 0); /* Make sure stderr is unbuffered */
  stdin_is_interactive = isatty(0);
  stdout_is_console = isatty(1);

#if USE_SYSTEM_SQLITE+0!=1
  if( strcmp(sqlite3_sourceid(),SQLITE_SOURCE_ID)!=0 ){
    utf8_printf(stderr, "SQLite header and source version mismatch\n%s\n%s\n",
            sqlite3_sourceid(), SQLITE_SOURCE_ID);
    exit(1);
  }
#endif
  main_init(&data);
#if !SQLITE_SHELL_IS_UTF8
  sqlite3_initialize();
  argv = sqlite3_malloc64(sizeof(argv[0])*argc);
  if( argv==0 ){
    raw_printf(stderr, "out of memory\n");
    exit(1);
  }
  for(i=0; i<argc; i++){
    argv[i] = sqlite3_win32_unicode_to_utf8(wargv[i]);
    if( argv[i]==0 ){
      raw_printf(stderr, "out of memory\n");
      exit(1);
    }
  }
#endif
  assert( argc>=1 && argv && argv[0] );
  Argv0 = argv[0];




  /* Make sure we have a valid signal handler early, before anything
  ** else is done.
  */
#ifdef SIGINT
  signal(SIGINT, interrupt_handler);
#endif

     || strcmp(z,"-cmd")==0
    ){
      (void)cmdline_option_value(argc, argv, ++i);
    }else if( strcmp(z,"-init")==0 ){
      zInitFile = cmdline_option_value(argc, argv, ++i);
    }else if( strcmp(z,"-batch")==0 ){
      /* Need to check for batch mode here to so we can avoid printing
      ** informational messages (like from process_sqliterc) before
      ** we do the actual processing of arguments later in a second pass.
      */
      stdin_is_interactive = 0;
    }else if( strcmp(z,"-heap")==0 ){
#if defined(SQLITE_ENABLE_MEMSYS3) || defined(SQLITE_ENABLE_MEMSYS5)
      const char *zSize;
      sqlite3_int64 szHeap;

      }
    }else{
      rc = process_input(&data, stdin);
    }
  }
  set_table_name(&data, 0);
  if( data.db ){
    session_close_all(&data);
    sqlite3_close(data.db);
  }
  sqlite3_free(data.zFreeOnClose);
#if !SQLITE_SHELL_IS_UTF8
  for(i=0; i<argc; i++) sqlite3_free(argv[i]);
  sqlite3_free(argv);
#endif
  return rc;
}

/******************************************************************************
** This file is an amalgamation of many separate C source files from SQLite
** version 3.13.0.  By combining all the individual C code files into this 
** single large file, the entire code can be compiled as a single translation
** unit.  This allows many compilers to do optimizations that would not be
** possible if the files were compiled separately.  Performance improvements
** of 5% or more are commonly seen when SQLite is compiled as a single
** translation unit.
**
** This file is all you need to compile SQLite.  To use SQLite in other

** string contains the date and time of the check-in (UTC) and an SHA1
** hash of the entire source tree.
**
** See also: [sqlite3_libversion()],
** [sqlite3_libversion_number()], [sqlite3_sourceid()],
** [sqlite_version()] and [sqlite_source_id()].
*/
#define SQLITE_VERSION        "3.13.0"
#define SQLITE_VERSION_NUMBER 3013000
#define SQLITE_SOURCE_ID      "2016-04-07 21:14:35 87aa9357fbe6749bae60e30af54ca16e48678802"

/*
** CAPI3REF: Run-Time Library Version Numbers
** KEYWORDS: sqlite3_version, sqlite3_sourceid
**
** These interfaces provide the same information as the [SQLITE_VERSION],
** [SQLITE_VERSION_NUMBER], and [SQLITE_SOURCE_ID] C preprocessor macros

/*
** CAPI3REF: Data Change Notification Callbacks
** METHOD: sqlite3
**
** ^The sqlite3_update_hook() interface registers a callback function
** with the [database connection] identified by the first argument
** to be invoked whenever a row is updated, inserted or deleted in
** a [rowid table].
** ^Any callback set by a previous call to this function
** for the same database connection is overridden.
**
** ^The second argument is a pointer to the function to invoke when a
** row is updated, inserted or deleted in a rowid table.
** ^The first argument to the callback is a copy of the third argument
** to sqlite3_update_hook().

** database connections for the meaning of "modify" in this paragraph.
**
** ^The sqlite3_update_hook(D,C,P) function
** returns the P argument from the previous call
** on the same [database connection] D, or NULL for
** the first call on D.
**
** See also the [sqlite3_commit_hook()], [sqlite3_rollback_hook()],
** and [sqlite3_preupdate_hook()] interfaces.
*/
SQLITE_API void *SQLITE_STDCALL sqlite3_update_hook(
  sqlite3*, 
  void(*)(void *,int ,char const *,char const *,sqlite3_int64),
  void*
);

** ^The S and M arguments passed to 
** sqlite3_backup_init(D,N,S,M) identify the [database connection]
** and database name of the source database, respectively.
** ^The source and destination [database connections] (parameters S and D)
** must be different or else sqlite3_backup_init(D,N,S,M) will fail with
** an error.
**
** ^A call to sqlite3_backup_init() will fail, returning NULL, if 
** there is already a read or read-write transaction open on the 
** destination database.
**
** ^If an error occurs within sqlite3_backup_init(D,N,S,M), then NULL is
** returned and an error code and error message are stored in the
** destination [database connection] D.
** ^The error code and message for the failed call to sqlite3_backup_init()

** ^Otherwise, if no error occurs, [sqlite3_db_cacheflush()] returns SQLITE_OK.
**
** ^This function does not set the database handle error code or message
** returned by the [sqlite3_errcode()] and [sqlite3_errmsg()] functions.
*/
SQLITE_API int SQLITE_STDCALL sqlite3_db_cacheflush(sqlite3*);

/*
** CAPI3REF: The pre-update hook.
**
** ^These interfaces are only available if SQLite is compiled using the
** [SQLITE_ENABLE_PREUPDATE_HOOK] compile-time option.
**
** ^The [sqlite3_preupdate_hook()] interface registers a callback function
** that is invoked prior to each [INSERT], [UPDATE], and [DELETE] operation
** on a [rowid table].
** ^At most one preupdate hook may be registered at a time on a single
** [database connection]; each call to [sqlite3_preupdate_hook()] overrides
** the previous setting.
** ^The preupdate hook is disabled by invoking [sqlite3_preupdate_hook()]
** with a NULL pointer as the second parameter.
** ^The third parameter to [sqlite3_preupdate_hook()] is passed through as
** the first parameter to callbacks.
**
** ^The preupdate hook only fires for changes to [rowid tables]; the preupdate
** hook is not invoked for changes to [virtual tables] or [WITHOUT ROWID]
** tables.
**
** ^The second parameter to the preupdate callback is a pointer to
** the [database connection] that registered the preupdate hook.
** ^The third parameter to the preupdate callback is one of the constants
** [SQLITE_INSERT], [SQLITE_DELETE], or [SQLITE_UPDATE] to indentify the
** kind of update operation that is about to occur.
** ^(The fourth parameter to the preupdate callback is the name of the
** database within the database connection that is being modified.  This
** will be "main" for the main database or "temp" for TEMP tables or 
** the name given after the AS keyword in the [ATTACH] statement for attached
** databases.)^
** ^The fifth parameter to the preupdate callback is the name of the
** table that is being modified.
** ^The sixth parameter to the preupdate callback is the initial [rowid] of the
** row being changes for SQLITE_UPDATE and SQLITE_DELETE changes and is
** undefined for SQLITE_INSERT changes.
** ^The seventh parameter to the preupdate callback is the final [rowid] of
** the row being changed for SQLITE_UPDATE and SQLITE_INSERT changes and is
** undefined for SQLITE_DELETE changes.
**
** The [sqlite3_preupdate_old()], [sqlite3_preupdate_new()],
** [sqlite3_preupdate_count()], and [sqlite3_preupdate_depth()] interfaces
** provide additional information about a preupdate event. These routines
** may only be called from within a preupdate callback.  Invoking any of
** these routines from outside of a preupdate callback or with a
** [database connection] pointer that is different from the one supplied
** to the preupdate callback results in undefined and probably undesirable
** behavior.
**
** ^The [sqlite3_preupdate_count(D)] interface returns the number of columns
** in the row that is being inserted, updated, or deleted.
**
** ^The [sqlite3_preupdate_old(D,N,P)] interface writes into P a pointer to
** a [protected sqlite3_value] that contains the value of the Nth column of
** the table row before it is updated.  The N parameter must be between 0
** and one less than the number of columns or the behavior will be
** undefined. This must only be used within SQLITE_UPDATE and SQLITE_DELETE
** preupdate callbacks; if it is used by an SQLITE_INSERT callback then the
** behavior is undefined.  The [sqlite3_value] that P points to
** will be destroyed when the preupdate callback returns.
**
** ^The [sqlite3_preupdate_new(D,N,P)] interface writes into P a pointer to
** a [protected sqlite3_value] that contains the value of the Nth column of
** the table row after it is updated.  The N parameter must be between 0
** and one less than the number of columns or the behavior will be
** undefined. This must only be used within SQLITE_INSERT and SQLITE_UPDATE
** preupdate callbacks; if it is used by an SQLITE_DELETE callback then the
** behavior is undefined.  The [sqlite3_value] that P points to
** will be destroyed when the preupdate callback returns.
**
** ^The [sqlite3_preupdate_depth(D)] interface returns 0 if the preupdate
** callback was invoked as a result of a direct insert, update, or delete
** operation; or 1 for inserts, updates, or deletes invoked by top-level 
** triggers; or 2 for changes resulting from triggers called by top-level
** triggers; and so forth.
**
** See also:  [sqlite3_update_hook()]
*/
SQLITE_API SQLITE_EXPERIMENTAL void *SQLITE_STDCALL sqlite3_preupdate_hook(
  sqlite3 *db,
  void(*xPreUpdate)(
    void *pCtx,                   /* Copy of third arg to preupdate_hook() */
    sqlite3 *db,                  /* Database handle */
    int op,                       /* SQLITE_UPDATE, DELETE or INSERT */
    char const *zDb,              /* Database name */
    char const *zName,            /* Table name */
    sqlite3_int64 iKey1,          /* Rowid of row about to be deleted/updated */
    sqlite3_int64 iKey2           /* New rowid value (for a rowid UPDATE) */
  ),
  void*
);
SQLITE_API SQLITE_EXPERIMENTAL int SQLITE_STDCALL sqlite3_preupdate_old(sqlite3 *, int, sqlite3_value **);
SQLITE_API SQLITE_EXPERIMENTAL int SQLITE_STDCALL sqlite3_preupdate_count(sqlite3 *);
SQLITE_API SQLITE_EXPERIMENTAL int SQLITE_STDCALL sqlite3_preupdate_depth(sqlite3 *);
SQLITE_API SQLITE_EXPERIMENTAL int SQLITE_STDCALL sqlite3_preupdate_new(sqlite3 *, int, sqlite3_value **);

/*
** CAPI3REF: Low-level system error code
**
** ^Attempt to return the underlying operating system error code or error
** number that caused the most recent I/O error or failure to open a file.
** The return value is OS-dependent.  For example, on unix systems, after
** [sqlite3_open_v2()] returns [SQLITE_CANTOPEN], this interface could be
** called to get back the underlying "errno" that caused the problem, such
** as ENOSPC, EAUTH, EISDIR, and so forth.  
*/
SQLITE_API int SQLITE_STDCALL sqlite3_system_errno(sqlite3*);

#endif

#if 0
}  /* End of the 'extern "C"' block */
#endif
#endif /* _SQLITE3_H_ */

/******** Begin file sqlite3rtree.h *********/
/*
** 2010 August 30
**
** The author disclaims copyright to this source code.  In place of
** a legal notice, here is a blessing:
**
**    May you do good and not evil.

#if 0
}  /* end of the 'extern "C"' block */
#endif

#endif  /* ifndef _SQLITE3RTREE_H_ */

/******** End of sqlite3rtree.h *********/
/******** Begin file sqlite3session.h *********/

#ifndef __SQLITESESSION_H_
#define __SQLITESESSION_H_ 1

/*
** Make sure we can call this stuff from C++.
*/
#if 0
extern "C" {
#endif


/*
** CAPI3REF: Session Object Handle
*/
typedef struct sqlite3_session sqlite3_session;

/*
** CAPI3REF: Changeset Iterator Handle
*/
typedef struct sqlite3_changeset_iter sqlite3_changeset_iter;

/*
** CAPI3REF: Create A New Session Object
**
** Create a new session object attached to database handle db. If successful,
** a pointer to the new object is written to *ppSession and SQLITE_OK is
** returned. If an error occurs, *ppSession is set to NULL and an SQLite
** error code (e.g. SQLITE_NOMEM) is returned.
**
** It is possible to create multiple session objects attached to a single
** database handle.
**
** Session objects created using this function should be deleted using the
** [sqlite3session_delete()] function before the database handle that they
** are attached to is itself closed. If the database handle is closed before
** the session object is deleted, then the results of calling any session
** module function, including [sqlite3session_delete()] on the session object
** are undefined.
**
** Because the session module uses the [sqlite3_preupdate_hook()] API, it
** is not possible for an application to register a pre-update hook on a
** database handle that has one or more session objects attached. Nor is
** it possible to create a session object attached to a database handle for
** which a pre-update hook is already defined. The results of attempting 
** either of these things are undefined.
**
** The session object will be used to create changesets for tables in
** database zDb, where zDb is either "main", or "temp", or the name of an
** attached database. It is not an error if database zDb is not attached
** to the database when the session object is created.
*/
int sqlite3session_create(
  sqlite3 *db,                    /* Database handle */
  const char *zDb,                /* Name of db (e.g. "main") */
  sqlite3_session **ppSession     /* OUT: New session object */
);

/*
** CAPI3REF: Delete A Session Object
**
** Delete a session object previously allocated using 
** [sqlite3session_create()]. Once a session object has been deleted, the
** results of attempting to use pSession with any other session module
** function are undefined.
**
** Session objects must be deleted before the database handle to which they
** are attached is closed. Refer to the documentation for 
** [sqlite3session_create()] for details.
*/
void sqlite3session_delete(sqlite3_session *pSession);


/*
** CAPI3REF: Enable Or Disable A Session Object
**
** Enable or disable the recording of changes by a session object. When
** enabled, a session object records changes made to the database. When
** disabled - it does not. A newly created session object is enabled.
** Refer to the documentation for [sqlite3session_changeset()] for further
** details regarding how enabling and disabling a session object affects
** the eventual changesets.
**
** Passing zero to this function disables the session. Passing a value
** greater than zero enables it. Passing a value less than zero is a 
** no-op, and may be used to query the current state of the session.
**
** The return value indicates the final state of the session object: 0 if 
** the session is disabled, or 1 if it is enabled.
*/
int sqlite3session_enable(sqlite3_session *pSession, int bEnable);

/*
** CAPI3REF: Set Or Clear the Indirect Change Flag
**
** Each change recorded by a session object is marked as either direct or
** indirect. A change is marked as indirect if either:
**
** <ul>
**   <li> The session object "indirect" flag is set when the change is
**        made, or
**   <li> The change is made by an SQL trigger or foreign key action 
**        instead of directly as a result of a users SQL statement.
** </ul>
**
** If a single row is affected by more than one operation within a session,
** then the change is considered indirect if all operations meet the criteria
** for an indirect change above, or direct otherwise.
**
** This function is used to set, clear or query the session object indirect
** flag.  If the second argument passed to this function is zero, then the
** indirect flag is cleared. If it is greater than zero, the indirect flag
** is set. Passing a value less than zero does not modify the current value
** of the indirect flag, and may be used to query the current state of the 
** indirect flag for the specified session object.
**
** The return value indicates the final state of the indirect flag: 0 if 
** it is clear, or 1 if it is set.
*/
int sqlite3session_indirect(sqlite3_session *pSession, int bIndirect);

/*
** CAPI3REF: Attach A Table To A Session Object
**
** If argument zTab is not NULL, then it is the name of a table to attach
** to the session object passed as the first argument. All subsequent changes 
** made to the table while the session object is enabled will be recorded. See 
** documentation for [sqlite3session_changeset()] for further details.
**
** Or, if argument zTab is NULL, then changes are recorded for all tables
** in the database. If additional tables are added to the database (by 
** executing "CREATE TABLE" statements) after this call is made, changes for 
** the new tables are also recorded.
**
** Changes can only be recorded for tables that have a PRIMARY KEY explicitly
** defined as part of their CREATE TABLE statement. It does not matter if the 
** PRIMARY KEY is an "INTEGER PRIMARY KEY" (rowid alias) or not. The PRIMARY
** KEY may consist of a single column, or may be a composite key.
** 
** It is not an error if the named table does not exist in the database. Nor
** is it an error if the named table does not have a PRIMARY KEY. However,
** no changes will be recorded in either of these scenarios.
**
** Changes are not recorded for individual rows that have NULL values stored
** in one or more of their PRIMARY KEY columns.
**
** SQLITE_OK is returned if the call completes without error. Or, if an error 
** occurs, an SQLite error code (e.g. SQLITE_NOMEM) is returned.
*/
int sqlite3session_attach(
  sqlite3_session *pSession,      /* Session object */
  const char *zTab                /* Table name */
);

/*
** CAPI3REF: Set a table filter on a Session Object.
**
** The second argument (xFilter) is the "filter callback". For changes to rows 
** in tables that are not attached to the Session oject, the filter is called
** to determine whether changes to the table's rows should be tracked or not. 
** If xFilter returns 0, changes is not tracked. Note that once a table is 
** attached, xFilter will not be called again.
*/
void sqlite3session_table_filter(
  sqlite3_session *pSession,      /* Session object */
  int(*xFilter)(
    void *pCtx,                   /* Copy of third arg to _filter_table() */
    const char *zTab              /* Table name */
  ),
  void *pCtx                      /* First argument passed to xFilter */
);

/*
** CAPI3REF: Generate A Changeset From A Session Object
**
** Obtain a changeset containing changes to the tables attached to the 
** session object passed as the first argument. If successful, 
** set *ppChangeset to point to a buffer containing the changeset 
** and *pnChangeset to the size of the changeset in bytes before returning
** SQLITE_OK. If an error occurs, set both *ppChangeset and *pnChangeset to
** zero and return an SQLite error code.
**
** A changeset consists of zero or more INSERT, UPDATE and/or DELETE changes,
** each representing a change to a single row of an attached table. An INSERT
** change contains the values of each field of a new database row. A DELETE
** contains the original values of each field of a deleted database row. An
** UPDATE change contains the original values of each field of an updated
** database row along with the updated values for each updated non-primary-key
** column. It is not possible for an UPDATE change to represent a change that
** modifies the values of primary key columns. If such a change is made, it
** is represented in a changeset as a DELETE followed by an INSERT.
**
** Changes are not recorded for rows that have NULL values stored in one or 
** more of their PRIMARY KEY columns. If such a row is inserted or deleted,
** no corresponding change is present in the changesets returned by this
** function. If an existing row with one or more NULL values stored in
** PRIMARY KEY columns is updated so that all PRIMARY KEY columns are non-NULL,
** only an INSERT is appears in the changeset. Similarly, if an existing row
** with non-NULL PRIMARY KEY values is updated so that one or more of its
** PRIMARY KEY columns are set to NULL, the resulting changeset contains a
** DELETE change only.
**
** The contents of a changeset may be traversed using an iterator created
** using the [sqlite3changeset_start()] API. A changeset may be applied to
** a database with a compatible schema using the [sqlite3changeset_apply()]
** API.
**
** Within a changeset generated by this function, all changes related to a
** single table are grouped together. In other words, when iterating through
** a changeset or when applying a changeset to a database, all changes related
** to a single table are processed before moving on to the next table. Tables
** are sorted in the same order in which they were attached (or auto-attached)
** to the sqlite3_session object. The order in which the changes related to
** a single table are stored is undefined.
**
** Following a successful call to this function, it is the responsibility of
** the caller to eventually free the buffer that *ppChangeset points to using
** [sqlite3_free()].
**
** <h3>Changeset Generation</h3>
**
** Once a table has been attached to a session object, the session object
** records the primary key values of all new rows inserted into the table.
** It also records the original primary key and other column values of any
** deleted or updated rows. For each unique primary key value, data is only
** recorded once - the first time a row with said primary key is inserted,
** updated or deleted in the lifetime of the session.
**
** There is one exception to the previous paragraph: when a row is inserted,
** updated or deleted, if one or more of its primary key columns contain a
** NULL value, no record of the change is made.
**
** The session object therefore accumulates two types of records - those
** that consist of primary key values only (created when the user inserts
** a new record) and those that consist of the primary key values and the
** original values of other table columns (created when the users deletes
** or updates a record).
**
** When this function is called, the requested changeset is created using
** both the accumulated records and the current contents of the database
** file. Specifically:
**
** <ul>
**   <li> For each record generated by an insert, the database is queried
**        for a row with a matching primary key. If one is found, an INSERT
**        change is added to the changeset. If no such row is found, no change 
**        is added to the changeset.
**
**   <li> For each record generated by an update or delete, the database is 
**        queried for a row with a matching primary key. If such a row is
**        found and one or more of the non-primary key fields have been
**        modified from their original values, an UPDATE change is added to 
**        the changeset. Or, if no such row is found in the table, a DELETE 
**        change is added to the changeset. If there is a row with a matching
**        primary key in the database, but all fields contain their original
**        values, no change is added to the changeset.
** </ul>
**
** This means, amongst other things, that if a row is inserted and then later
** deleted while a session object is active, neither the insert nor the delete
** will be present in the changeset. Or if a row is deleted and then later a 
** row with the same primary key values inserted while a session object is
** active, the resulting changeset will contain an UPDATE change instead of
** a DELETE and an INSERT.
**
** When a session object is disabled (see the [sqlite3session_enable()] API),
** it does not accumulate records when rows are inserted, updated or deleted.
** This may appear to have some counter-intuitive effects if a single row
** is written to more than once during a session. For example, if a row
** is inserted while a session object is enabled, then later deleted while 
** the same session object is disabled, no INSERT record will appear in the
** changeset, even though the delete took place while the session was disabled.
** Or, if one field of a row is updated while a session is disabled, and 
** another field of the same row is updated while the session is enabled, the
** resulting changeset will contain an UPDATE change that updates both fields.
*/
int sqlite3session_changeset(
  sqlite3_session *pSession,      /* Session object */
  int *pnChangeset,               /* OUT: Size of buffer at *ppChangeset */
  void **ppChangeset              /* OUT: Buffer containing changeset */
);

/*
** CAPI3REF: Load The Difference Between Tables Into A Session 
**
** If it is not already attached to the session object passed as the first
** argument, this function attaches table zTbl in the same manner as the
** [sqlite3session_attach()] function. If zTbl does not exist, or if it
** does not have a primary key, this function is a no-op (but does not return
** an error).
**
** Argument zFromDb must be the name of a database ("main", "temp" etc.)
** attached to the same database handle as the session object that contains 
** a table compatible with the table attached to the session by this function.
** A table is considered compatible if it:
**
** <ul>
**   <li> Has the same name,
**   <li> Has the same set of columns declared in the same order, and
**   <li> Has the same PRIMARY KEY definition.
** </ul>
**
** If the tables are not compatible, SQLITE_SCHEMA is returned. If the tables
** are compatible but do not have any PRIMARY KEY columns, it is not an error
** but no changes are added to the session object. As with other session
** APIs, tables without PRIMARY KEYs are simply ignored.
**
** This function adds a set of changes to the session object that could be
** used to update the table in database zFrom (call this the "from-table") 
** so that its content is the same as the table attached to the session 
** object (call this the "to-table"). Specifically:
**
** <ul>
**   <li> For each row (primary key) that exists in the to-table but not in 
**     the from-table, an INSERT record is added to the session object.
**
**   <li> For each row (primary key) that exists in the to-table but not in 
**     the from-table, a DELETE record is added to the session object.
**
**   <li> For each row (primary key) that exists in both tables, but features 
**     different in each, an UPDATE record is added to the session.
** </ul>
**
** To clarify, if this function is called and then a changeset constructed
** using [sqlite3session_changeset()], then after applying that changeset to 
** database zFrom the contents of the two compatible tables would be 
** identical.
**
** It an error if database zFrom does not exist or does not contain the
** required compatible table.
**
** If the operation successful, SQLITE_OK is returned. Otherwise, an SQLite
** error code. In this case, if argument pzErrMsg is not NULL, *pzErrMsg
** may be set to point to a buffer containing an English language error 
** message. It is the responsibility of the caller to free this buffer using
** sqlite3_free().
*/
int sqlite3session_diff(
  sqlite3_session *pSession,
  const char *zFromDb,
  const char *zTbl,
  char **pzErrMsg
);


/*
** CAPI3REF: Generate A Patchset From A Session Object
**
** The differences between a patchset and a changeset are that:
**
** <ul>
**   <li> DELETE records consist of the primary key fields only. The 
**        original values of other fields are omitted.
**   <li> The original values of any modified fields are omitted from 
**        UPDATE records.
** </ul>
**
** A patchset blob may be used with up to date versions of all 
** sqlite3changeset_xxx API functions except for sqlite3changeset_invert(), 
** which returns SQLITE_CORRUPT if it is passed a patchset. Similarly,
** attempting to use a patchset blob with old versions of the
** sqlite3changeset_xxx APIs also provokes an SQLITE_CORRUPT error. 
**
** Because the non-primary key "old.*" fields are omitted, no 
** SQLITE_CHANGESET_DATA conflicts can be detected or reported if a patchset
** is passed to the sqlite3changeset_apply() API. Other conflict types work
** in the same way as for changesets.
**
** Changes within a patchset are ordered in the same way as for changesets
** generated by the sqlite3session_changeset() function (i.e. all changes for
** a single table are grouped together, tables appear in the order in which
** they were attached to the session object).
*/
int sqlite3session_patchset(
  sqlite3_session *pSession,      /* Session object */
  int *pnPatchset,                /* OUT: Size of buffer at *ppChangeset */
  void **ppPatchset               /* OUT: Buffer containing changeset */
);

/*
** CAPI3REF: Test if a changeset has recorded any changes.
**
** Return non-zero if no changes to attached tables have been recorded by 
** the session object passed as the first argument. Otherwise, if one or 
** more changes have been recorded, return zero.
**
** Even if this function returns zero, it is possible that calling
** [sqlite3session_changeset()] on the session handle may still return a
** changeset that contains no changes. This can happen when a row in 
** an attached table is modified and then later on the original values 
** are restored. However, if this function returns non-zero, then it is
** guaranteed that a call to sqlite3session_changeset() will return a 
** changeset containing zero changes.
*/
int sqlite3session_isempty(sqlite3_session *pSession);

/*
** CAPI3REF: Create An Iterator To Traverse A Changeset 
**
** Create an iterator used to iterate through the contents of a changeset.
** If successful, *pp is set to point to the iterator handle and SQLITE_OK
** is returned. Otherwise, if an error occurs, *pp is set to zero and an
** SQLite error code is returned.
**
** The following functions can be used to advance and query a changeset 
** iterator created by this function:
**
** <ul>
**   <li> [sqlite3changeset_next()]
**   <li> [sqlite3changeset_op()]
**   <li> [sqlite3changeset_new()]
**   <li> [sqlite3changeset_old()]
** </ul>
**
** It is the responsibility of the caller to eventually destroy the iterator
** by passing it to [sqlite3changeset_finalize()]. The buffer containing the
** changeset (pChangeset) must remain valid until after the iterator is
** destroyed.
**
** Assuming the changeset blob was created by one of the
** [sqlite3session_changeset()], [sqlite3changeset_concat()] or
** [sqlite3changeset_invert()] functions, all changes within the changeset 
** that apply to a single table are grouped together. This means that when 
** an application iterates through a changeset using an iterator created by 
** this function, all changes that relate to a single table are visted 
** consecutively. There is no chance that the iterator will visit a change 
** the applies to table X, then one for table Y, and then later on visit 
** another change for table X.
*/
int sqlite3changeset_start(
  sqlite3_changeset_iter **pp,    /* OUT: New changeset iterator handle */
  int nChangeset,                 /* Size of changeset blob in bytes */
  void *pChangeset                /* Pointer to blob containing changeset */
);


/*
** CAPI3REF: Advance A Changeset Iterator
**
** This function may only be used with iterators created by function
** [sqlite3changeset_start()]. If it is called on an iterator passed to
** a conflict-handler callback by [sqlite3changeset_apply()], SQLITE_MISUSE
** is returned and the call has no effect.
**
** Immediately after an iterator is created by sqlite3changeset_start(), it
** does not point to any change in the changeset. Assuming the changeset
** is not empty, the first call to this function advances the iterator to
** point to the first change in the changeset. Each subsequent call advances
** the iterator to point to the next change in the changeset (if any). If
** no error occurs and the iterator points to a valid change after a call
** to sqlite3changeset_next() has advanced it, SQLITE_ROW is returned. 
** Otherwise, if all changes in the changeset have already been visited,
** SQLITE_DONE is returned.
**
** If an error occurs, an SQLite error code is returned. Possible error 
** codes include SQLITE_CORRUPT (if the changeset buffer is corrupt) or 
** SQLITE_NOMEM.
*/
int sqlite3changeset_next(sqlite3_changeset_iter *pIter);

/*
** CAPI3REF: Obtain The Current Operation From A Changeset Iterator
**
** The pIter argument passed to this function may either be an iterator
** passed to a conflict-handler by [sqlite3changeset_apply()], or an iterator
** created by [sqlite3changeset_start()]. In the latter case, the most recent
** call to [sqlite3changeset_next()] must have returned [SQLITE_ROW]. If this
** is not the case, this function returns [SQLITE_MISUSE].
**
** If argument pzTab is not NULL, then *pzTab is set to point to a
** nul-terminated utf-8 encoded string containing the name of the table
** affected by the current change. The buffer remains valid until either
** sqlite3changeset_next() is called on the iterator or until the 
** conflict-handler function returns. If pnCol is not NULL, then *pnCol is 
** set to the number of columns in the table affected by the change. If
** pbIncorrect is not NULL, then *pbIndirect is set to true (1) if the change
** is an indirect change, or false (0) otherwise. See the documentation for
** [sqlite3session_indirect()] for a description of direct and indirect
** changes. Finally, if pOp is not NULL, then *pOp is set to one of 
** [SQLITE_INSERT], [SQLITE_DELETE] or [SQLITE_UPDATE], depending on the 
** type of change that the iterator currently points to.
**
** If no error occurs, SQLITE_OK is returned. If an error does occur, an
** SQLite error code is returned. The values of the output variables may not
** be trusted in this case.
*/
int sqlite3changeset_op(
  sqlite3_changeset_iter *pIter,  /* Iterator object */
  const char **pzTab,             /* OUT: Pointer to table name */
  int *pnCol,                     /* OUT: Number of columns in table */
  int *pOp,                       /* OUT: SQLITE_INSERT, DELETE or UPDATE */
  int *pbIndirect                 /* OUT: True for an 'indirect' change */
);

/*
** CAPI3REF: Obtain The Primary Key Definition Of A Table
**
** For each modified table, a changeset includes the following:
**
** <ul>
**   <li> The number of columns in the table, and
**   <li> Which of those columns make up the tables PRIMARY KEY.
** </ul>
**
** This function is used to find which columns comprise the PRIMARY KEY of
** the table modified by the change that iterator pIter currently points to.
** If successful, *pabPK is set to point to an array of nCol entries, where
** nCol is the number of columns in the table. Elements of *pabPK are set to
** 0x01 if the corresponding column is part of the tables primary key, or
** 0x00 if it is not.
**
** If argumet pnCol is not NULL, then *pnCol is set to the number of columns
** in the table.
**
** If this function is called when the iterator does not point to a valid
** entry, SQLITE_MISUSE is returned and the output variables zeroed. Otherwise,
** SQLITE_OK is returned and the output variables populated as described
** above.
*/
int sqlite3changeset_pk(
  sqlite3_changeset_iter *pIter,  /* Iterator object */
  unsigned char **pabPK,          /* OUT: Array of boolean - true for PK cols */
  int *pnCol                      /* OUT: Number of entries in output array */
);

/*
** CAPI3REF: Obtain old.* Values From A Changeset Iterator
**
** The pIter argument passed to this function may either be an iterator
** passed to a conflict-handler by [sqlite3changeset_apply()], or an iterator
** created by [sqlite3changeset_start()]. In the latter case, the most recent
** call to [sqlite3changeset_next()] must have returned SQLITE_ROW. 
** Furthermore, it may only be called if the type of change that the iterator
** currently points to is either [SQLITE_DELETE] or [SQLITE_UPDATE]. Otherwise,
** this function returns [SQLITE_MISUSE] and sets *ppValue to NULL.
**
** Argument iVal must be greater than or equal to 0, and less than the number
** of columns in the table affected by the current change. Otherwise,
** [SQLITE_RANGE] is returned and *ppValue is set to NULL.
**
** If successful, this function sets *ppValue to point to a protected
** sqlite3_value object containing the iVal'th value from the vector of 
** original row values stored as part of the UPDATE or DELETE change and
** returns SQLITE_OK. The name of the function comes from the fact that this 
** is similar to the "old.*" columns available to update or delete triggers.
**
** If some other error occurs (e.g. an OOM condition), an SQLite error code
** is returned and *ppValue is set to NULL.
*/
int sqlite3changeset_old(
  sqlite3_changeset_iter *pIter,  /* Changeset iterator */
  int iVal,                       /* Column number */
  sqlite3_value **ppValue         /* OUT: Old value (or NULL pointer) */
);

/*
** CAPI3REF: Obtain new.* Values From A Changeset Iterator
**
** The pIter argument passed to this function may either be an iterator
** passed to a conflict-handler by [sqlite3changeset_apply()], or an iterator
** created by [sqlite3changeset_start()]. In the latter case, the most recent
** call to [sqlite3changeset_next()] must have returned SQLITE_ROW. 
** Furthermore, it may only be called if the type of change that the iterator
** currently points to is either [SQLITE_UPDATE] or [SQLITE_INSERT]. Otherwise,
** this function returns [SQLITE_MISUSE] and sets *ppValue to NULL.
**
** Argument iVal must be greater than or equal to 0, and less than the number
** of columns in the table affected by the current change. Otherwise,
** [SQLITE_RANGE] is returned and *ppValue is set to NULL.
**
** If successful, this function sets *ppValue to point to a protected
** sqlite3_value object containing the iVal'th value from the vector of 
** new row values stored as part of the UPDATE or INSERT change and
** returns SQLITE_OK. If the change is an UPDATE and does not include
** a new value for the requested column, *ppValue is set to NULL and 
** SQLITE_OK returned. The name of the function comes from the fact that 
** this is similar to the "new.*" columns available to update or delete 
** triggers.
**
** If some other error occurs (e.g. an OOM condition), an SQLite error code
** is returned and *ppValue is set to NULL.
*/
int sqlite3changeset_new(
  sqlite3_changeset_iter *pIter,  /* Changeset iterator */
  int iVal,                       /* Column number */
  sqlite3_value **ppValue         /* OUT: New value (or NULL pointer) */
);

/*
** CAPI3REF: Obtain Conflicting Row Values From A Changeset Iterator
**
** This function should only be used with iterator objects passed to a
** conflict-handler callback by [sqlite3changeset_apply()] with either
** [SQLITE_CHANGESET_DATA] or [SQLITE_CHANGESET_CONFLICT]. If this function
** is called on any other iterator, [SQLITE_MISUSE] is returned and *ppValue
** is set to NULL.
**
** Argument iVal must be greater than or equal to 0, and less than the number
** of columns in the table affected by the current change. Otherwise,
** [SQLITE_RANGE] is returned and *ppValue is set to NULL.
**
** If successful, this function sets *ppValue to point to a protected
** sqlite3_value object containing the iVal'th value from the 
** "conflicting row" associated with the current conflict-handler callback
** and returns SQLITE_OK.
**
** If some other error occurs (e.g. an OOM condition), an SQLite error code
** is returned and *ppValue is set to NULL.
*/
int sqlite3changeset_conflict(
  sqlite3_changeset_iter *pIter,  /* Changeset iterator */
  int iVal,                       /* Column number */
  sqlite3_value **ppValue         /* OUT: Value from conflicting row */
);

/*
** CAPI3REF: Determine The Number Of Foreign Key Constraint Violations
**
** This function may only be called with an iterator passed to an
** SQLITE_CHANGESET_FOREIGN_KEY conflict handler callback. In this case
** it sets the output variable to the total number of known foreign key
** violations in the destination database and returns SQLITE_OK.
**
** In all other cases this function returns SQLITE_MISUSE.
*/
int sqlite3changeset_fk_conflicts(
  sqlite3_changeset_iter *pIter,  /* Changeset iterator */
  int *pnOut                      /* OUT: Number of FK violations */
);


/*
** CAPI3REF: Finalize A Changeset Iterator
**
** This function is used to finalize an iterator allocated with
** [sqlite3changeset_start()].
**
** This function should only be called on iterators created using the
** [sqlite3changeset_start()] function. If an application calls this
** function with an iterator passed to a conflict-handler by
** [sqlite3changeset_apply()], [SQLITE_MISUSE] is immediately returned and the
** call has no effect.
**
** If an error was encountered within a call to an sqlite3changeset_xxx()
** function (for example an [SQLITE_CORRUPT] in [sqlite3changeset_next()] or an 
** [SQLITE_NOMEM] in [sqlite3changeset_new()]) then an error code corresponding
** to that error is returned by this function. Otherwise, SQLITE_OK is
** returned. This is to allow the following pattern (pseudo-code):
**
**   sqlite3changeset_start();
**   while( SQLITE_ROW==sqlite3changeset_next() ){
**     // Do something with change.
**   }
**   rc = sqlite3changeset_finalize();
**   if( rc!=SQLITE_OK ){
**     // An error has occurred 
**   }
*/
int sqlite3changeset_finalize(sqlite3_changeset_iter *pIter);

/*
** CAPI3REF: Invert A Changeset
**
** This function is used to "invert" a changeset object. Applying an inverted
** changeset to a database reverses the effects of applying the uninverted
** changeset. Specifically:
**
** <ul>
**   <li> Each DELETE change is changed to an INSERT, and
**   <li> Each INSERT change is changed to a DELETE, and
**   <li> For each UPDATE change, the old.* and new.* values are exchanged.
** </ul>
**
** This function does not change the order in which changes appear within
** the changeset. It merely reverses the sense of each individual change.
**
** If successful, a pointer to a buffer containing the inverted changeset
** is stored in *ppOut, the size of the same buffer is stored in *pnOut, and
** SQLITE_OK is returned. If an error occurs, both *pnOut and *ppOut are
** zeroed and an SQLite error code returned.
**
** It is the responsibility of the caller to eventually call sqlite3_free()
** on the *ppOut pointer to free the buffer allocation following a successful 
** call to this function.
**
** WARNING/TODO: This function currently assumes that the input is a valid
** changeset. If it is not, the results are undefined.
*/
int sqlite3changeset_invert(
  int nIn, const void *pIn,       /* Input changeset */
  int *pnOut, void **ppOut        /* OUT: Inverse of input */
);

/*
** CAPI3REF: Concatenate Two Changeset Objects
**
** This function is used to concatenate two changesets, A and B, into a 
** single changeset. The result is a changeset equivalent to applying
** changeset A followed by changeset B. 
**
** This function combines the two input changesets using an 
** sqlite3_changegroup object. Calling it produces similar results as the
** following code fragment:
**
**   sqlite3_changegroup *pGrp;
**   rc = sqlite3_changegroup_new(&pGrp);
**   if( rc==SQLITE_OK ) rc = sqlite3changegroup_add(pGrp, nA, pA);
**   if( rc==SQLITE_OK ) rc = sqlite3changegroup_add(pGrp, nB, pB);
**   if( rc==SQLITE_OK ){
**     rc = sqlite3changegroup_output(pGrp, pnOut, ppOut);
**   }else{
**     *ppOut = 0;
**     *pnOut = 0;
**   }
**
** Refer to the sqlite3_changegroup documentation below for details.
*/
int sqlite3changeset_concat(
  int nA,                         /* Number of bytes in buffer pA */
  void *pA,                       /* Pointer to buffer containing changeset A */
  int nB,                         /* Number of bytes in buffer pB */
  void *pB,                       /* Pointer to buffer containing changeset B */
  int *pnOut,                     /* OUT: Number of bytes in output changeset */
  void **ppOut                    /* OUT: Buffer containing output changeset */
);


/*
** Changegroup handle.
*/
typedef struct sqlite3_changegroup sqlite3_changegroup;

/*
** CAPI3REF: Combine two or more changesets into a single changeset.
**
** An sqlite3_changegroup object is used to combine two or more changesets
** (or patchsets) into a single changeset (or patchset). A single changegroup
** object may combine changesets or patchsets, but not both. The output is
** always in the same format as the input.
**
** If successful, this function returns SQLITE_OK and populates (*pp) with
** a pointer to a new sqlite3_changegroup object before returning. The caller
** should eventually free the returned object using a call to 
** sqlite3changegroup_delete(). If an error occurs, an SQLite error code
** (i.e. SQLITE_NOMEM) is returned and *pp is set to NULL.
**
** The usual usage pattern for an sqlite3_changegroup object is as follows:
**
** <ul>
**   <li> It is created using a call to sqlite3changegroup_new().
**
**   <li> Zero or more changesets (or patchsets) are added to the object
**        by calling sqlite3changegroup_add().
**
**   <li> The result of combining all input changesets together is obtained 
**        by the application via a call to sqlite3changegroup_output().
**
**   <li> The object is deleted using a call to sqlite3changegroup_delete().
** </ul>
**
** Any number of calls to add() and output() may be made between the calls to
** new() and delete(), and in any order.
**
** As well as the regular sqlite3changegroup_add() and 
** sqlite3changegroup_output() functions, also available are the streaming
** versions sqlite3changegroup_add_strm() and sqlite3changegroup_output_strm().
*/
int sqlite3changegroup_new(sqlite3_changegroup **pp);

/*
** Add all changes within the changeset (or patchset) in buffer pData (size
** nData bytes) to the changegroup. 
**
** If the buffer contains a patchset, then all prior calls to this function
** on the same changegroup object must also have specified patchsets. Or, if
** the buffer contains a changeset, so must have the earlier calls to this
** function. Otherwise, SQLITE_ERROR is returned and no changes are added
** to the changegroup.
**
** Rows within the changeset and changegroup are identified by the values in
** their PRIMARY KEY columns. A change in the changeset is considered to
** apply to the same row as a change already present in the changegroup if
** the two rows have the same primary key.
**
** Changes to rows that that do not already appear in the changegroup are
** simply copied into it. Or, if both the new changeset and the changegroup
** contain changes that apply to a single row, the final contents of the
** changegroup depends on the type of each change, as follows:
**
** <table border=1 style="margin-left:8ex;margin-right:8ex">
**   <tr><th style="white-space:pre">Existing Change  </th>
**       <th style="white-space:pre">New Change       </th>
**       <th>Output Change
**   <tr><td>INSERT <td>INSERT <td>
**       The new change is ignored. This case does not occur if the new
**       changeset was recorded immediately after the changesets already
**       added to the changegroup.
**   <tr><td>INSERT <td>UPDATE <td>
**       The INSERT change remains in the changegroup. The values in the 
**       INSERT change are modified as if the row was inserted by the
**       existing change and then updated according to the new change.
**   <tr><td>INSERT <td>DELETE <td>
**       The existing INSERT is removed from the changegroup. The DELETE is
**       not added.
**   <tr><td>UPDATE <td>INSERT <td>
**       The new change is ignored. This case does not occur if the new
**       changeset was recorded immediately after the changesets already
**       added to the changegroup.
**   <tr><td>UPDATE <td>UPDATE <td>
**       The existing UPDATE remains within the changegroup. It is amended 
**       so that the accompanying values are as if the row was updated once 
**       by the existing change and then again by the new change.
**   <tr><td>UPDATE <td>DELETE <td>
**       The existing UPDATE is replaced by the new DELETE within the
**       changegroup.
**   <tr><td>DELETE <td>INSERT <td>
**       If one or more of the column values in the row inserted by the
**       new change differ from those in the row deleted by the existing 
**       change, the existing DELETE is replaced by an UPDATE within the
**       changegroup. Otherwise, if the inserted row is exactly the same 
**       as the deleted row, the existing DELETE is simply discarded.
**   <tr><td>DELETE <td>UPDATE <td>
**       The new change is ignored. This case does not occur if the new
**       changeset was recorded immediately after the changesets already
**       added to the changegroup.
**   <tr><td>DELETE <td>DELETE <td>
**       The new change is ignored. This case does not occur if the new
**       changeset was recorded immediately after the changesets already
**       added to the changegroup.
** </table>
**
** If the new changeset contains changes to a table that is already present
** in the changegroup, then the number of columns and the position of the
** primary key columns for the table must be consistent. If this is not the
** case, this function fails with SQLITE_SCHEMA. If the input changeset
** appears to be corrupt and the corruption is detected, SQLITE_CORRUPT is
** returned. Or, if an out-of-memory condition occurs during processing, this
** function returns SQLITE_NOMEM. In all cases, if an error occurs the
** final contents of the changegroup is undefined.
**
** If no error occurs, SQLITE_OK is returned.
*/
int sqlite3changegroup_add(sqlite3_changegroup*, int nData, void *pData);

/*
** Obtain a buffer containing a changeset (or patchset) representing the
** current contents of the changegroup. If the inputs to the changegroup
** were themselves changesets, the output is a changeset. Or, if the
** inputs were patchsets, the output is also a patchset.
**
** As with the output of the sqlite3session_changeset() and
** sqlite3session_patchset() functions, all changes related to a single
** table are grouped together in the output of this function. Tables appear
** in the same order as for the very first changeset added to the changegroup.
** If the second or subsequent changesets added to the changegroup contain
** changes for tables that do not appear in the first changeset, they are
** appended onto the end of the output changeset, again in the order in
** which they are first encountered.
**
** If an error occurs, an SQLite error code is returned and the output
** variables (*pnData) and (*ppData) are set to 0. Otherwise, SQLITE_OK
** is returned and the output variables are set to the size of and a 
** pointer to the output buffer, respectively. In this case it is the
** responsibility of the caller to eventually free the buffer using a
** call to sqlite3_free().
*/
int sqlite3changegroup_output(
  sqlite3_changegroup*,
  int *pnData,                    /* OUT: Size of output buffer in bytes */
  void **ppData                   /* OUT: Pointer to output buffer */
);

/*
** Delete a changegroup object.
*/
void sqlite3changegroup_delete(sqlite3_changegroup*);

/*
** CAPI3REF: Apply A Changeset To A Database
**
** Apply a changeset to a database. This function attempts to update the
** "main" database attached to handle db with the changes found in the
** changeset passed via the second and third arguments.
**
** The fourth argument (xFilter) passed to this function is the "filter
** callback". If it is not NULL, then for each table affected by at least one
** change in the changeset, the filter callback is invoked with
** the table name as the second argument, and a copy of the context pointer
** passed as the sixth argument to this function as the first. If the "filter
** callback" returns zero, then no attempt is made to apply any changes to 
** the table. Otherwise, if the return value is non-zero or the xFilter
** argument to this function is NULL, all changes related to the table are
** attempted.
**
** For each table that is not excluded by the filter callback, this function 
** tests that the target database contains a compatible table. A table is 
** considered compatible if all of the following are true:
**
** <ul>
**   <li> The table has the same name as the name recorded in the 
**        changeset, and
**   <li> The table has the same number of columns as recorded in the 
**        changeset, and
**   <li> The table has primary key columns in the same position as 
**        recorded in the changeset.
** </ul>
**
** If there is no compatible table, it is not an error, but none of the
** changes associated with the table are applied. A warning message is issued
** via the sqlite3_log() mechanism with the error code SQLITE_SCHEMA. At most
** one such warning is issued for each table in the changeset.
**
** For each change for which there is a compatible table, an attempt is made 
** to modify the table contents according to the UPDATE, INSERT or DELETE 
** change. If a change cannot be applied cleanly, the conflict handler 
** function passed as the fifth argument to sqlite3changeset_apply() may be 
** invoked. A description of exactly when the conflict handler is invoked for 
** each type of change is below.
**
** Unlike the xFilter argument, xConflict may not be passed NULL. The results
** of passing anything other than a valid function pointer as the xConflict
** argument are undefined.
**
** Each time the conflict handler function is invoked, it must return one
** of [SQLITE_CHANGESET_OMIT], [SQLITE_CHANGESET_ABORT] or 
** [SQLITE_CHANGESET_REPLACE]. SQLITE_CHANGESET_REPLACE may only be returned
** if the second argument passed to the conflict handler is either
** SQLITE_CHANGESET_DATA or SQLITE_CHANGESET_CONFLICT. If the conflict-handler
** returns an illegal value, any changes already made are rolled back and
** the call to sqlite3changeset_apply() returns SQLITE_MISUSE. Different 
** actions are taken by sqlite3changeset_apply() depending on the value
** returned by each invocation of the conflict-handler function. Refer to
** the documentation for the three 
** [SQLITE_CHANGESET_OMIT|available return values] for details.
**
** <dl>
** <dt>DELETE Changes<dd>
**   For each DELETE change, this function checks if the target database 
**   contains a row with the same primary key value (or values) as the 
**   original row values stored in the changeset. If it does, and the values 
**   stored in all non-primary key columns also match the values stored in 
**   the changeset the row is deleted from the target database.
**
**   If a row with matching primary key values is found, but one or more of
**   the non-primary key fields contains a value different from the original
**   row value stored in the changeset, the conflict-handler function is
**   invoked with [SQLITE_CHANGESET_DATA] as the second argument.
**
**   If no row with matching primary key values is found in the database,
**   the conflict-handler function is invoked with [SQLITE_CHANGESET_NOTFOUND]
**   passed as the second argument.
**
**   If the DELETE operation is attempted, but SQLite returns SQLITE_CONSTRAINT
**   (which can only happen if a foreign key constraint is violated), the
**   conflict-handler function is invoked with [SQLITE_CHANGESET_CONSTRAINT]
**   passed as the second argument. This includes the case where the DELETE
**   operation is attempted because an earlier call to the conflict handler
**   function returned [SQLITE_CHANGESET_REPLACE].
**
** <dt>INSERT Changes<dd>
**   For each INSERT change, an attempt is made to insert the new row into
**   the database.
**
**   If the attempt to insert the row fails because the database already 
**   contains a row with the same primary key values, the conflict handler
**   function is invoked with the second argument set to 
**   [SQLITE_CHANGESET_CONFLICT].
**
**   If the attempt to insert the row fails because of some other constraint
**   violation (e.g. NOT NULL or UNIQUE), the conflict handler function is 
**   invoked with the second argument set to [SQLITE_CHANGESET_CONSTRAINT].
**   This includes the case where the INSERT operation is re-attempted because 
**   an earlier call to the conflict handler function returned 
**   [SQLITE_CHANGESET_REPLACE].
**
** <dt>UPDATE Changes<dd>
**   For each UPDATE change, this function checks if the target database 
**   contains a row with the same primary key value (or values) as the 
**   original row values stored in the changeset. If it does, and the values 
**   stored in all non-primary key columns also match the values stored in 
**   the changeset the row is updated within the target database.
**
**   If a row with matching primary key values is found, but one or more of
**   the non-primary key fields contains a value different from an original
**   row value stored in the changeset, the conflict-handler function is
**   invoked with [SQLITE_CHANGESET_DATA] as the second argument. Since
**   UPDATE changes only contain values for non-primary key fields that are
**   to be modified, only those fields need to match the original values to
**   avoid the SQLITE_CHANGESET_DATA conflict-handler callback.
**
**   If no row with matching primary key values is found in the database,
**   the conflict-handler function is invoked with [SQLITE_CHANGESET_NOTFOUND]
**   passed as the second argument.
**
**   If the UPDATE operation is attempted, but SQLite returns 
**   SQLITE_CONSTRAINT, the conflict-handler function is invoked with 
**   [SQLITE_CHANGESET_CONSTRAINT] passed as the second argument.
**   This includes the case where the UPDATE operation is attempted after 
**   an earlier call to the conflict handler function returned
**   [SQLITE_CHANGESET_REPLACE].  
** </dl>
**
** It is safe to execute SQL statements, including those that write to the
** table that the callback related to, from within the xConflict callback.
** This can be used to further customize the applications conflict
** resolution strategy.
**
** All changes made by this function are enclosed in a savepoint transaction.
** If any other error (aside from a constraint failure when attempting to
** write to the target database) occurs, then the savepoint transaction is
** rolled back, restoring the target database to its original state, and an 
** SQLite error code returned.
*/
int sqlite3changeset_apply(
  sqlite3 *db,                    /* Apply change to "main" db of this handle */
  int nChangeset,                 /* Size of changeset in bytes */
  void *pChangeset,               /* Changeset blob */
  int(*xFilter)(
    void *pCtx,                   /* Copy of sixth arg to _apply() */
    const char *zTab              /* Table name */
  ),
  int(*xConflict)(
    void *pCtx,                   /* Copy of sixth arg to _apply() */
    int eConflict,                /* DATA, MISSING, CONFLICT, CONSTRAINT */
    sqlite3_changeset_iter *p     /* Handle describing change and conflict */
  ),
  void *pCtx                      /* First argument passed to xConflict */
);

/* 
** CAPI3REF: Constants Passed To The Conflict Handler
**
** Values that may be passed as the second argument to a conflict-handler.
**
** <dl>
** <dt>SQLITE_CHANGESET_DATA<dd>
**   The conflict handler is invoked with CHANGESET_DATA as the second argument
**   when processing a DELETE or UPDATE change if a row with the required
**   PRIMARY KEY fields is present in the database, but one or more other 
**   (non primary-key) fields modified by the update do not contain the 
**   expected "before" values.
** 
**   The conflicting row, in this case, is the database row with the matching
**   primary key.
** 
** <dt>SQLITE_CHANGESET_NOTFOUND<dd>
**   The conflict handler is invoked with CHANGESET_NOTFOUND as the second
**   argument when processing a DELETE or UPDATE change if a row with the
**   required PRIMARY KEY fields is not present in the database.
** 
**   There is no conflicting row in this case. The results of invoking the
**   sqlite3changeset_conflict() API are undefined.
** 
** <dt>SQLITE_CHANGESET_CONFLICT<dd>
**   CHANGESET_CONFLICT is passed as the second argument to the conflict
**   handler while processing an INSERT change if the operation would result 
**   in duplicate primary key values.
** 
**   The conflicting row in this case is the database row with the matching
**   primary key.
**
** <dt>SQLITE_CHANGESET_FOREIGN_KEY<dd>
**   If foreign key handling is enabled, and applying a changeset leaves the
**   database in a state containing foreign key violations, the conflict 
**   handler is invoked with CHANGESET_FOREIGN_KEY as the second argument
**   exactly once before the changeset is committed. If the conflict handler
**   returns CHANGESET_OMIT, the changes, including those that caused the
**   foreign key constraint violation, are committed. Or, if it returns
**   CHANGESET_ABORT, the changeset is rolled back.
**
**   No current or conflicting row information is provided. The only function
**   it is possible to call on the supplied sqlite3_changeset_iter handle
**   is sqlite3changeset_fk_conflicts().
** 
** <dt>SQLITE_CHANGESET_CONSTRAINT<dd>
**   If any other constraint violation occurs while applying a change (i.e. 
**   a UNIQUE, CHECK or NOT NULL constraint), the conflict handler is 
**   invoked with CHANGESET_CONSTRAINT as the second argument.
** 
**   There is no conflicting row in this case. The results of invoking the
**   sqlite3changeset_conflict() API are undefined.
**
** </dl>
*/
#define SQLITE_CHANGESET_DATA        1
#define SQLITE_CHANGESET_NOTFOUND    2
#define SQLITE_CHANGESET_CONFLICT    3
#define SQLITE_CHANGESET_CONSTRAINT  4
#define SQLITE_CHANGESET_FOREIGN_KEY 5

/* 
** CAPI3REF: Constants Returned By The Conflict Handler
**
** A conflict handler callback must return one of the following three values.
**
** <dl>
** <dt>SQLITE_CHANGESET_OMIT<dd>
**   If a conflict handler returns this value no special action is taken. The
**   change that caused the conflict is not applied. The session module 
**   continues to the next change in the changeset.
**
** <dt>SQLITE_CHANGESET_REPLACE<dd>
**   This value may only be returned if the second argument to the conflict
**   handler was SQLITE_CHANGESET_DATA or SQLITE_CHANGESET_CONFLICT. If this
**   is not the case, any changes applied so far are rolled back and the 
**   call to sqlite3changeset_apply() returns SQLITE_MISUSE.
**
**   If CHANGESET_REPLACE is returned by an SQLITE_CHANGESET_DATA conflict
**   handler, then the conflicting row is either updated or deleted, depending
**   on the type of change.
**
**   If CHANGESET_REPLACE is returned by an SQLITE_CHANGESET_CONFLICT conflict
**   handler, then the conflicting row is removed from the database and a
**   second attempt to apply the change is made. If this second attempt fails,
**   the original row is restored to the database before continuing.
**
** <dt>SQLITE_CHANGESET_ABORT<dd>
**   If this value is returned, any changes applied so far are rolled back 
**   and the call to sqlite3changeset_apply() returns SQLITE_ABORT.
** </dl>
*/
#define SQLITE_CHANGESET_OMIT       0
#define SQLITE_CHANGESET_REPLACE    1
#define SQLITE_CHANGESET_ABORT      2

/*
** CAPI3REF: Streaming Versions of API functions.
**
** The six streaming API xxx_strm() functions serve similar purposes to the 
** corresponding non-streaming API functions:
**
** <table border=1 style="margin-left:8ex;margin-right:8ex">
**   <tr><th>Streaming function<th>Non-streaming equivalent</th>
**   <tr><td>sqlite3changeset_apply_str<td>[sqlite3changeset_apply] 
**   <tr><td>sqlite3changeset_concat_str<td>[sqlite3changeset_concat] 
**   <tr><td>sqlite3changeset_invert_str<td>[sqlite3changeset_invert] 
**   <tr><td>sqlite3changeset_start_str<td>[sqlite3changeset_start] 
**   <tr><td>sqlite3session_changeset_str<td>[sqlite3session_changeset] 
**   <tr><td>sqlite3session_patchset_str<td>[sqlite3session_patchset] 
** </table>
**
** Non-streaming functions that accept changesets (or patchsets) as input
** require that the entire changeset be stored in a single buffer in memory. 
** Similarly, those that return a changeset or patchset do so by returning 
** a pointer to a single large buffer allocated using sqlite3_malloc(). 
** Normally this is convenient. However, if an application running in a 
** low-memory environment is required to handle very large changesets, the
** large contiguous memory allocations required can become onerous.
**
** In order to avoid this problem, instead of a single large buffer, input
** is passed to a streaming API functions by way of a callback function that
** the sessions module invokes to incrementally request input data as it is
** required. In all cases, a pair of API function parameters such as
**
**  <pre>
**  &nbsp;     int nChangeset,
**  &nbsp;     void *pChangeset,
**  </pre>
**
** Is replaced by:
**
**  <pre>
**  &nbsp;     int (*xInput)(void *pIn, void *pData, int *pnData),
**  &nbsp;     void *pIn,
**  </pre>
**
** Each time the xInput callback is invoked by the sessions module, the first
** argument passed is a copy of the supplied pIn context pointer. The second 
** argument, pData, points to a buffer (*pnData) bytes in size. Assuming no 
** error occurs the xInput method should copy up to (*pnData) bytes of data 
** into the buffer and set (*pnData) to the actual number of bytes copied 
** before returning SQLITE_OK. If the input is completely exhausted, (*pnData) 
** should be set to zero to indicate this. Or, if an error occurs, an SQLite 
** error code should be returned. In all cases, if an xInput callback returns
** an error, all processing is abandoned and the streaming API function
** returns a copy of the error code to the caller.
**
** In the case of sqlite3changeset_start_strm(), the xInput callback may be
** invoked by the sessions module at any point during the lifetime of the
** iterator. If such an xInput callback returns an error, the iterator enters
** an error state, whereby all subsequent calls to iterator functions 
** immediately fail with the same error code as returned by xInput.
**
** Similarly, streaming API functions that return changesets (or patchsets)
** return them in chunks by way of a callback function instead of via a
** pointer to a single large buffer. In this case, a pair of parameters such
** as:
**
**  <pre>
**  &nbsp;     int *pnChangeset,
**  &nbsp;     void **ppChangeset,
**  </pre>
**
** Is replaced by:
**
**  <pre>
**  &nbsp;     int (*xOutput)(void *pOut, const void *pData, int nData),
**  &nbsp;     void *pOut
**  </pre>
**
** The xOutput callback is invoked zero or more times to return data to
** the application. The first parameter passed to each call is a copy of the
** pOut pointer supplied by the application. The second parameter, pData,
** points to a buffer nData bytes in size containing the chunk of output
** data being returned. If the xOutput callback successfully processes the
** supplied data, it should return SQLITE_OK to indicate success. Otherwise,
** it should return some other SQLite error code. In this case processing
** is immediately abandoned and the streaming API function returns a copy
** of the xOutput error code to the application.
**
** The sessions module never invokes an xOutput callback with the third 
** parameter set to a value less than or equal to zero. Other than this,
** no guarantees are made as to the size of the chunks of data returned.
*/
int sqlite3changeset_apply_strm(
  sqlite3 *db,                    /* Apply change to "main" db of this handle */
  int (*xInput)(void *pIn, void *pData, int *pnData), /* Input function */
  void *pIn,                                          /* First arg for xInput */
  int(*xFilter)(
    void *pCtx,                   /* Copy of sixth arg to _apply() */
    const char *zTab              /* Table name */
  ),
  int(*xConflict)(
    void *pCtx,                   /* Copy of sixth arg to _apply() */
    int eConflict,                /* DATA, MISSING, CONFLICT, CONSTRAINT */
    sqlite3_changeset_iter *p     /* Handle describing change and conflict */
  ),
  void *pCtx                      /* First argument passed to xConflict */
);
int sqlite3changeset_concat_strm(
  int (*xInputA)(void *pIn, void *pData, int *pnData),
  void *pInA,
  int (*xInputB)(void *pIn, void *pData, int *pnData),
  void *pInB,
  int (*xOutput)(void *pOut, const void *pData, int nData),
  void *pOut
);
int sqlite3changeset_invert_strm(
  int (*xInput)(void *pIn, void *pData, int *pnData),
  void *pIn,
  int (*xOutput)(void *pOut, const void *pData, int nData),
  void *pOut
);
int sqlite3changeset_start_strm(
  sqlite3_changeset_iter **pp,
  int (*xInput)(void *pIn, void *pData, int *pnData),
  void *pIn
);
int sqlite3session_changeset_strm(
  sqlite3_session *pSession,
  int (*xOutput)(void *pOut, const void *pData, int nData),
  void *pOut
);
int sqlite3session_patchset_strm(
  sqlite3_session *pSession,
  int (*xOutput)(void *pOut, const void *pData, int nData),
  void *pOut
);
int sqlite3changegroup_add_strm(sqlite3_changegroup*, 
    int (*xInput)(void *pIn, void *pData, int *pnData),
    void *pIn
);
int sqlite3changegroup_output_strm(sqlite3_changegroup*,
    int (*xOutput)(void *pOut, const void *pData, int nData), 
    void *pOut
);


/*
** Make sure we can call this stuff from C++.
*/
#if 0
}
#endif

#endif  /* SQLITE_ENABLE_SESSION && SQLITE_ENABLE_PREUPDATE_HOOK */

/******** End of sqlite3session.h *********/
/******** Begin file fts5.h *********/
/*
** 2014 May 31
**
** The author disclaims copyright to this source code.  In place of
** a legal notice, here is a blessing:
**
**    May you do good and not evil.

#if 0
}  /* end of the 'extern "C"' block */
#endif

#endif /* _FTS5_H */


/******** End of fts5.h *********/

/************** End of sqlite3.h *********************************************/
/************** Continuing where we left off in sqliteInt.h ******************/

/*
** Include the configuration header output by 'configure' if we're using the
** autoconf-based build

typedef struct KeyClass KeyClass;
typedef struct KeyInfo KeyInfo;
typedef struct Lookaside Lookaside;
typedef struct LookasideSlot LookasideSlot;
typedef struct Module Module;
typedef struct NameContext NameContext;
typedef struct Parse Parse;
typedef struct PreUpdate PreUpdate;
typedef struct PrintfArguments PrintfArguments;
typedef struct RowSet RowSet;
typedef struct Savepoint Savepoint;
typedef struct Select Select;
typedef struct SQLiteThread SQLiteThread;
typedef struct SelectDest SelectDest;
typedef struct SrcList SrcList;

    sqlite3_context *pCtx; /* Used when p4type is P4_FUNCCTX */
    CollSeq *pColl;        /* Used when p4type is P4_COLLSEQ */
    Mem *pMem;             /* Used when p4type is P4_MEM */
    VTable *pVtab;         /* Used when p4type is P4_VTAB */
    KeyInfo *pKeyInfo;     /* Used when p4type is P4_KEYINFO */
    int *ai;               /* Used when p4type is P4_INTARRAY */
    SubProgram *pProgram;  /* Used when p4type is P4_SUBPROGRAM */
    Table *pTab;           /* Used when p4type is P4_TABLE */
#ifdef SQLITE_ENABLE_CURSOR_HINTS
    Expr *pExpr;           /* Used when p4type is P4_EXPR */
#endif
    int (*xAdvance)(BtCursor *, int *);
  } p4;
#ifdef SQLITE_ENABLE_EXPLAIN_COMMENTS
  char *zComment;          /* Comment to improve readability */

#define P4_MPRINTF  (-11) /* P4 is a string obtained from sqlite3_mprintf() */
#define P4_REAL     (-12) /* P4 is a 64-bit floating point value */
#define P4_INT64    (-13) /* P4 is a 64-bit signed integer */
#define P4_INT32    (-14) /* P4 is a 32-bit signed integer */
#define P4_INTARRAY (-15) /* P4 is a vector of 32-bit integers */
#define P4_SUBPROGRAM  (-18) /* P4 is a pointer to a SubProgram structure */
#define P4_ADVANCE  (-19) /* P4 is a pointer to BtreeNext() or BtreePrev() */
#define P4_TABLE    (-20) /* P4 is a pointer to a Table structure */
#define P4_FUNCCTX  (-21) /* P4 is a pointer to an sqlite3_context object */

/* Error message codes for OP_Halt */
#define P5_ConstraintNotNull 1
#define P5_ConstraintUnique  2
#define P5_ConstraintCheck   3
#define P5_ConstraintFK      4

  void *pProfileArg;                        /* Argument to profile function */
  void *pCommitArg;                 /* Argument to xCommitCallback() */
  int (*xCommitCallback)(void*);    /* Invoked at every commit. */
  void *pRollbackArg;               /* Argument to xRollbackCallback() */
  void (*xRollbackCallback)(void*); /* Invoked at every commit. */
  void *pUpdateArg;
  void (*xUpdateCallback)(void*,int, const char*,const char*,sqlite_int64);
#ifdef SQLITE_ENABLE_PREUPDATE_HOOK
  void *pPreUpdateArg;          /* First argument to xPreUpdateCallback */
  void (*xPreUpdateCallback)(   /* Registered using sqlite3_preupdate_hook() */
    void*,sqlite3*,int,char const*,char const*,sqlite3_int64,sqlite3_int64
  );
  PreUpdate *pPreUpdate;        /* Context for active pre-update callback */
#endif /* SQLITE_ENABLE_PREUPDATE_HOOK */
#ifndef SQLITE_OMIT_WAL
  int (*xWalCallback)(void *, sqlite3 *, const char *, int);
  void *pWalArg;
#endif
  void(*xCollNeeded)(void*,sqlite3*,int eTextRep,const char*);
  void(*xCollNeeded16)(void*,sqlite3*,int eTextRep,const void*);
  void *pCollNeededArg;

#define OPFLAG_NCHANGE       0x01    /* OP_Insert: Set to update db->nChange */
                                     /* Also used in P2 (not P5) of OP_Delete */
#define OPFLAG_EPHEM         0x01    /* OP_Column: Ephemeral output is ok */
#define OPFLAG_LASTROWID     0x02    /* Set to update db->lastRowid */
#define OPFLAG_ISUPDATE      0x04    /* This OP_Insert is an sql UPDATE */
#define OPFLAG_APPEND        0x08    /* This is likely to be an append */
#define OPFLAG_USESEEKRESULT 0x10    /* Try to avoid a seek in BtreeInsert() */
#ifdef SQLITE_ENABLE_PREUPDATE_HOOK
#define OPFLAG_ISNOOP        0x40    /* OP_Delete does pre-update-hook only */
#endif
#define OPFLAG_LENGTHARG     0x40    /* OP_Column only used for length() */
#define OPFLAG_TYPEOFARG     0x80    /* OP_Column only used for typeof() */
#define OPFLAG_BULKCSR       0x01    /* OP_Open** used to open bulk cursor */
#define OPFLAG_SEEKEQ        0x02    /* OP_Open** cursor uses EQ seek only */
#define OPFLAG_FORDELETE     0x08    /* OP_Open should use BTREE_FORDELETE */
#define OPFLAG_P2ISREG       0x10    /* P2 to OP_Open** is a register number */
#define OPFLAG_PERMUTE       0x01    /* OP_Compare: use the permutation */

SQLITE_PRIVATE void sqlite3Pragma(Parse*,Token*,Token*,Token*,int);
SQLITE_PRIVATE void sqlite3ResetAllSchemasOfConnection(sqlite3*);
SQLITE_PRIVATE void sqlite3ResetOneSchema(sqlite3*,int);
SQLITE_PRIVATE void sqlite3CollapseDatabaseArray(sqlite3*);
SQLITE_PRIVATE void sqlite3CommitInternalChanges(sqlite3*);
SQLITE_PRIVATE void sqlite3DeleteColumnNames(sqlite3*,Table*);
SQLITE_PRIVATE int sqlite3ColumnsFromExprList(Parse*,ExprList*,i16*,Column**);
SQLITE_PRIVATE void sqlite3SelectAddColumnTypeAndCollation(Parse*,Table*,Select*);
SQLITE_PRIVATE Table *sqlite3ResultSetOfSelect(Parse*,Select*);
SQLITE_PRIVATE void sqlite3OpenMasterTable(Parse *, int);
SQLITE_PRIVATE Index *sqlite3PrimaryKeyIndex(Table*);
SQLITE_PRIVATE i16 sqlite3ColumnOfIndex(Index*, i16);
SQLITE_PRIVATE void sqlite3StartTable(Parse*,Token*,Token*,int,int,int,int);
#if SQLITE_ENABLE_HIDDEN_COLUMNS
SQLITE_PRIVATE   void sqlite3ColumnPropertiesFromName(Table*, Column*);

** The following are allowed values for Vdbe.magic
*/
#define VDBE_MAGIC_INIT     0x26bceaa5    /* Building a VDBE program */
#define VDBE_MAGIC_RUN      0xbdf20da3    /* VDBE is ready to execute */
#define VDBE_MAGIC_HALT     0x519c2973    /* VDBE has completed execution */
#define VDBE_MAGIC_DEAD     0xb606c3c8    /* The VDBE has been deallocated */

/*
** Structure used to store the context required by the 
** sqlite3_preupdate_*() API functions.
*/
struct PreUpdate {
  Vdbe *v;
  VdbeCursor *pCsr;               /* Cursor to read old values from */
  int op;                         /* One of SQLITE_INSERT, UPDATE, DELETE */
  u8 *aRecord;                    /* old.* database record */
  KeyInfo keyinfo;
  UnpackedRecord *pUnpacked;      /* Unpacked version of aRecord[] */
  UnpackedRecord *pNewUnpacked;   /* Unpacked version of new.* record */
  int iNewReg;                    /* Register for new.* values */
  i64 iKey1;                      /* First key value passed to hook */
  i64 iKey2;                      /* Second key value passed to hook */
  int iPKey;                      /* If not negative index of IPK column */
  Mem *aNew;                      /* Array of new.* values */
};

/*
** Function prototypes
*/
SQLITE_PRIVATE void sqlite3VdbeError(Vdbe*, const char *, ...);
SQLITE_PRIVATE void sqlite3VdbeFreeCursor(Vdbe *, VdbeCursor*);
void sqliteVdbePopStack(Vdbe*,int);
SQLITE_PRIVATE int sqlite3VdbeCursorMoveto(VdbeCursor**, int*);

SQLITE_PRIVATE int sqlite3VdbeMemFinalize(Mem*, FuncDef*);
SQLITE_PRIVATE const char *sqlite3OpcodeName(int);
SQLITE_PRIVATE int sqlite3VdbeMemGrow(Mem *pMem, int n, int preserve);
SQLITE_PRIVATE int sqlite3VdbeMemClearAndResize(Mem *pMem, int n);
SQLITE_PRIVATE int sqlite3VdbeCloseStatement(Vdbe *, int);
SQLITE_PRIVATE void sqlite3VdbeFrameDelete(VdbeFrame*);
SQLITE_PRIVATE int sqlite3VdbeFrameRestore(VdbeFrame *);
#ifdef SQLITE_ENABLE_PREUPDATE_HOOK
SQLITE_PRIVATE void sqlite3VdbePreUpdateHook(Vdbe*,VdbeCursor*,int,const char*,Table*,i64,int);
#endif
SQLITE_PRIVATE int sqlite3VdbeTransferError(Vdbe *p);

SQLITE_PRIVATE int sqlite3VdbeSorterInit(sqlite3 *, int, VdbeCursor *);
SQLITE_PRIVATE void sqlite3VdbeSorterReset(sqlite3 *, VdbeSorter *);
SQLITE_PRIVATE void sqlite3VdbeSorterClose(sqlite3 *, VdbeCursor *);
SQLITE_PRIVATE int sqlite3VdbeSorterRowkey(const VdbeCursor *, Mem *);
SQLITE_PRIVATE int sqlite3VdbeSorterNext(sqlite3 *, const VdbeCursor *, int *);

** Convert a LogEst into an integer.
**
** Note that this routine is only used when one or more of various
** non-standard compile-time options is enabled.
*/
SQLITE_PRIVATE u64 sqlite3LogEstToInt(LogEst x){
  u64 n;

  n = x%10;
  x /= 10;
  if( n>=5 ) n -= 2;
  else if( n>=1 ) n -= 1;
#if defined(SQLITE_ENABLE_STMT_SCANSTATUS) || \
    defined(SQLITE_EXPLAIN_ESTIMATED_ROWS)
  if( x>60 ) return (u64)LARGEST_INT64;

** routine to lower a locking level.
*/
static int unixLock(sqlite3_file *id, int eFileLock){
  /* The following describes the implementation of the various locks and
  ** lock transitions in terms of the POSIX advisory shared and exclusive
  ** lock primitives (called read-locks and write-locks below, to avoid
  ** confusion with SQLite lock names). The algorithms are complicated
  ** slightly in order to be compatible with Windows95 systems simultaneously
  ** accessing the same database file, in case that is ever required.
  **
  ** Symbols defined in os.h indentify the 'pending byte' and the 'reserved
  ** byte', each single bytes at well known offsets, and the 'shared byte
  ** range', a range of 510 bytes at a well known offset.
  **
  ** To obtain a SHARED lock, a read-lock is obtained on the 'pending
  ** byte'.  If this is successful, 'shared byte range' is read-locked
  ** and the lock on the 'pending byte' released.  (Legacy note:  When
  ** SQLite was first developed, Windows95 systems were still very common,
  ** and Widnows95 lacks a shared-lock capability.  So on Windows95, a
  ** single randomly selected by from the 'shared byte range' is locked.
  ** Windows95 is now pretty much extinct, but this work-around for the
  ** lack of shared-locks on Windows95 lives on, for backwards
  ** compatibility.)
  **
  ** A process may only obtain a RESERVED lock after it has a SHARED lock.
  ** A RESERVED lock is implemented by grabbing a write-lock on the
  ** 'reserved byte'. 
  **
  ** A process may only obtain a PENDING lock after it has obtained a
  ** SHARED lock. A PENDING lock is implemented by obtaining a write-lock
  ** on the 'pending byte'. This ensures that no new SHARED locks can be
  ** obtained, but existing SHARED locks are allowed to persist. A process
  ** does not have to obtain a RESERVED lock on the way to a PENDING lock.
  ** This property is used by the algorithm for rolling back a journal file
  ** after a crash.
  **
  ** An EXCLUSIVE lock, obtained after a PENDING lock is held, is
  ** implemented by obtaining a write-lock on the entire 'shared byte
  ** range'. Since all other locks require a read-lock on one of the bytes
  ** within this range, this ensures that no other locks are held on the
  ** database. 





  */
  int rc = SQLITE_OK;
  unixFile *pFile = (unixFile*)id;
  unixInodeInfo *pInode;
  struct flock lock;
  int tErrno = 0;

*/

SQLITE_API void SQLITE_STDCALL sqlite3_win32_write_debug(const char *zBuf, int nBuf){
  char zDbgBuf[SQLITE_WIN32_DBG_BUF_SIZE];
  int nMin = MIN(nBuf, (SQLITE_WIN32_DBG_BUF_SIZE - 1)); /* may be negative. */
  if( nMin<-1 ) nMin = -1; /* all negative values become -1. */
  assert( nMin==-1 || nMin==0 || nMin<SQLITE_WIN32_DBG_BUF_SIZE );
#ifdef SQLITE_ENABLE_API_ARMOR
  if( !zBuf ){
    (void)SQLITE_MISUSE_BKPT;
    return;
  }
#endif
#if defined(SQLITE_WIN32_HAS_ANSI)
  if( nMin>0 ){
    memset(zDbgBuf, 0, SQLITE_WIN32_DBG_BUF_SIZE);
    memcpy(zDbgBuf, zBuf, nMin);
    osOutputDebugStringA(zDbgBuf);
  }else{
    osOutputDebugStringA(zBuf);

SQLITE_PRIVATE void sqlite3MemSetDefault(void){
  sqlite3_config(SQLITE_CONFIG_MALLOC, sqlite3MemGetWin32());
}
#endif /* SQLITE_WIN32_MALLOC */

/*
** Convert a UTF-8 string to Microsoft Unicode.
**
** Space to hold the returned string is obtained from sqlite3_malloc().
*/
static LPWSTR winUtf8ToUnicode(const char *zText){
  int nChar;
  LPWSTR zWideText;

  nChar = osMultiByteToWideChar(CP_UTF8, 0, zText, -1, NULL, 0);
  if( nChar==0 ){
    return 0;
  }
  zWideText = sqlite3MallocZero( nChar*sizeof(WCHAR) );
  if( zWideText==0 ){
    return 0;
  }
  nChar = osMultiByteToWideChar(CP_UTF8, 0, zText, -1, zWideText,
                                nChar);
  if( nChar==0 ){
    sqlite3_free(zWideText);
    zWideText = 0;
  }
  return zWideText;
}

/*
** Convert a Microsoft Unicode string to UTF-8.
**
** Space to hold the returned string is obtained from sqlite3_malloc().
*/
static char *winUnicodeToUtf8(LPCWSTR zWideText){
  int nByte;
  char *zText;

  nByte = osWideCharToMultiByte(CP_UTF8, 0, zWideText, -1, 0, 0, 0, 0);
  if( nByte == 0 ){
    return 0;
  }
  zText = sqlite3MallocZero( nByte );
  if( zText==0 ){
    return 0;
  }
  nByte = osWideCharToMultiByte(CP_UTF8, 0, zWideText, -1, zText, nByte,
                                0, 0);
  if( nByte == 0 ){
    sqlite3_free(zText);
    zText = 0;
  }
  return zText;
}

/*
** Convert an ANSI string to Microsoft Unicode, using the ANSI or OEM
** code page.
**
** Space to hold the returned string is obtained from sqlite3_malloc().

*/
static LPWSTR winMbcsToUnicode(const char *zText, int useAnsi){
  int nByte;
  LPWSTR zMbcsText;
  int codepage = useAnsi ? CP_ACP : CP_OEMCP;

  nByte = osMultiByteToWideChar(codepage, 0, zText, -1, NULL,
                                0)*sizeof(WCHAR);
  if( nByte==0 ){
    return 0;
  }
  zMbcsText = sqlite3MallocZero( nByte*sizeof(WCHAR) );
  if( zMbcsText==0 ){
    return 0;
  }
  nByte = osMultiByteToWideChar(codepage, 0, zText, -1, zMbcsText,
                                nByte);
  if( nByte==0 ){
    sqlite3_free(zMbcsText);
    zMbcsText = 0;
  }
  return zMbcsText;
}

/*
** Convert a Microsoft Unicode string to a multi-byte character string,
** using the ANSI or OEM code page.
**
** Space to hold the returned string is obtained from sqlite3_malloc().
*/
static char *winUnicodeToMbcs(LPCWSTR zWideText, int useAnsi){
  int nByte;
  char *zText;
  int codepage = useAnsi ? CP_ACP : CP_OEMCP;

  nByte = osWideCharToMultiByte(codepage, 0, zWideText, -1, 0, 0, 0, 0);
  if( nByte == 0 ){
    return 0;
  }
  zText = sqlite3MallocZero( nByte );
  if( zText==0 ){
    return 0;
  }
  nByte = osWideCharToMultiByte(codepage, 0, zWideText, -1, zText,
                                nByte, 0, 0);
  if( nByte == 0 ){
    sqlite3_free(zText);
    zText = 0;
  }
  return zText;
}

/*
** Convert a multi-byte character string to UTF-8.

**
** Space to hold the returned string is obtained from sqlite3_malloc().

*/
static char *winMbcsToUtf8(const char *zText, int useAnsi){

  char *zTextUtf8;

  LPWSTR zTmpWide;


  zTmpWide = winMbcsToUnicode(zText, useAnsi);
  if( zTmpWide==0 ){
    return 0;
  }
  zTextUtf8 = winUnicodeToUtf8(zTmpWide);
  sqlite3_free(zTmpWide);

  return zTextUtf8;
}

/*
** Convert a UTF-8 string to a multi-byte character string.
**
** Space to hold the returned string is obtained from sqlite3_malloc().
*/
static char *winUtf8ToMbcs(const char *zText, int useAnsi){
  char *zTextMbcs;
  LPWSTR zTmpWide;

  zTmpWide = winUtf8ToUnicode(zText);
  if( zTmpWide==0 ){
    return 0;
  }
  zTextMbcs = winUnicodeToMbcs(zTmpWide, useAnsi);
  sqlite3_free(zTmpWide);
  return zTextMbcs;
}

/*
** This is a public wrapper for the winUtf8ToUnicode() function.
*/
SQLITE_API LPWSTR SQLITE_STDCALL sqlite3_win32_utf8_to_unicode(const char *zText){
#ifdef SQLITE_ENABLE_API_ARMOR
  if( !zText ){
    (void)SQLITE_MISUSE_BKPT;
    return 0;
  }
#endif
#ifndef SQLITE_OMIT_AUTOINIT
  if( sqlite3_initialize() ) return 0;
#endif
  return winUtf8ToUnicode(zText);
}

/*
** This is a public wrapper for the winUnicodeToUtf8() function.
*/
SQLITE_API char *SQLITE_STDCALL sqlite3_win32_unicode_to_utf8(LPCWSTR zWideText){
#ifdef SQLITE_ENABLE_API_ARMOR
  if( !zWideText ){
    (void)SQLITE_MISUSE_BKPT;
    return 0;
  }
#endif
#ifndef SQLITE_OMIT_AUTOINIT
  if( sqlite3_initialize() ) return 0;
#endif
  return winUnicodeToUtf8(zWideText);
}

/*
** This is a public wrapper for the winMbcsToUtf8() function.
*/
SQLITE_API char *SQLITE_STDCALL sqlite3_win32_mbcs_to_utf8(const char *zText){
#ifdef SQLITE_ENABLE_API_ARMOR
  if( !zText ){
    (void)SQLITE_MISUSE_BKPT;
    return 0;
  }
#endif
#ifndef SQLITE_OMIT_AUTOINIT
  if( sqlite3_initialize() ) return 0;
#endif
  return winMbcsToUtf8(zText, osAreFileApisANSI());
}


/*
** This is a public wrapper for the winMbcsToUtf8() function.
*/
SQLITE_API char *SQLITE_STDCALL sqlite3_win32_mbcs_to_utf8_v2(const char *zText, int useAnsi){


#ifdef SQLITE_ENABLE_API_ARMOR

  if( !zText ){
    (void)SQLITE_MISUSE_BKPT;
    return 0;
  }

#endif
#ifndef SQLITE_OMIT_AUTOINIT
  if( sqlite3_initialize() ) return 0;
#endif
  return winMbcsToUtf8(zText, useAnsi);
}

/*
** This is a public wrapper for the winUtf8ToMbcs() function.

*/
SQLITE_API char *SQLITE_STDCALL sqlite3_win32_utf8_to_mbcs(const char *zText){
#ifdef SQLITE_ENABLE_API_ARMOR
  if( !zText ){
    (void)SQLITE_MISUSE_BKPT;
    return 0;
  }
#endif
#ifndef SQLITE_OMIT_AUTOINIT
  if( sqlite3_initialize() ) return 0;
#endif
  return winUtf8ToMbcs(zText, osAreFileApisANSI());
}

/*
** This is a public wrapper for the winUtf8ToMbcs() function.
*/
SQLITE_API char *SQLITE_STDCALL sqlite3_win32_utf8_to_mbcs_v2(const char *zText, int useAnsi){
#ifdef SQLITE_ENABLE_API_ARMOR
  if( !zText ){
    (void)SQLITE_MISUSE_BKPT;
    return 0;
  }

#endif
#ifndef SQLITE_OMIT_AUTOINIT
  if( sqlite3_initialize() ) return 0;
#endif
  return winUtf8ToMbcs(zText, useAnsi);
}

/*
** This function sets the data directory or the temporary directory based on
** the provided arguments.  The type argument must be 1 in order to set the
** data directory or 2 in order to set the temporary directory.  The zValue
** argument is the name of the directory to use.  The return value will be

                             0,
                             (LPSTR) &zTemp,
                             0,
                             0);
    if( dwLen > 0 ){
      /* allocate a buffer and convert to UTF8 */
      sqlite3BeginBenignMalloc();
      zOut = winMbcsToUtf8(zTemp, osAreFileApisANSI());
      sqlite3EndBenignMalloc();
      /* free the system buffer allocated by FormatMessage */
      osLocalFree(zTemp);
    }
  }
#endif
  if( 0 == dwLen ){

static char *winConvertToUtf8Filename(const void *zFilename){
  char *zConverted = 0;
  if( osIsNT() ){
    zConverted = winUnicodeToUtf8(zFilename);
  }
#ifdef SQLITE_WIN32_HAS_ANSI
  else{
    zConverted = winMbcsToUtf8(zFilename, osAreFileApisANSI());
  }
#endif
  /* caller will handle out of memory */
  return zConverted;
}
#endif

/*
** Convert a UTF-8 filename into whatever form the underlying
** operating system wants filenames in.  Space to hold the result
** is obtained from malloc and must be freed by the calling
** function.
*/
static void *winConvertFromUtf8Filename(const char *zFilename){
  void *zConverted = 0;
  if( osIsNT() ){
    zConverted = winUtf8ToUnicode(zFilename);
  }
#ifdef SQLITE_WIN32_HAS_ANSI
  else{
    zConverted = winUtf8ToMbcs(zFilename, osAreFileApisANSI());
  }
#endif
  /* caller will handle out of memory */
  return zConverted;
}

/*

    }
    if( osGetTempPathA(nMax, zMbcsPath)==0 ){
      sqlite3_free(zBuf);
      OSTRACE(("TEMP-FILENAME rc=SQLITE_IOERR_GETTEMPPATH\n"));
      return winLogError(SQLITE_IOERR_GETTEMPPATH, osGetLastError(),
                         "winGetTempname3", 0);
    }
    zUtf8 = winMbcsToUtf8(zMbcsPath, osAreFileApisANSI());
    if( zUtf8 ){
      sqlite3_snprintf(nMax, zBuf, "%s", zUtf8);
      sqlite3_free(zUtf8);
    }else{
      sqlite3_free(zBuf);
      OSTRACE(("TEMP-FILENAME rc=SQLITE_IOERR_NOMEM\n"));
      return SQLITE_IOERR_NOMEM_BKPT;

    if( nByte==0 ){
      sqlite3_free(zConverted);
      sqlite3_free(zTemp);
      return winLogError(SQLITE_CANTOPEN_FULLPATH, osGetLastError(),
                         "winFullPathname4", zRelative);
    }
    sqlite3_free(zConverted);
    zOut = winMbcsToUtf8(zTemp, osAreFileApisANSI());
    sqlite3_free(zTemp);
  }
#endif
  if( zOut ){
    sqlite3_snprintf(MIN(nFull, pVfs->mxPathname), zFull, "%s", zOut);
    sqlite3_free(zOut);
    return SQLITE_OK;

  int iEnd = iFirst + nCell;
  assert( CORRUPT_DB || pPg->hdrOffset==0 );    /* Never called on page 1 */
  for(i=iFirst; i<iEnd; i++){
    int sz, rc;
    u8 *pSlot;
    sz = cachedCellSize(pCArray, i);
    if( (aData[1]==0 && aData[2]==0) || (pSlot = pageFindSlot(pPg,sz,&rc))==0 ){
      if( (pData - pBegin)<sz ) return 1;
      pData -= sz;

      pSlot = pData;
    }
    /* pSlot and pCArray->apCell[i] will never overlap on a well-formed
    ** database.  But they might for a corrupt database.  Hence use memmove()
    ** since memcpy() sends SIGABORT with overlapping buffers on OpenBSD */
    assert( (pSlot+sz)<=pCArray->apCell[i]
         || pSlot>=(pCArray->apCell[i]+sz)

  put2byte(&aData[hdr+3], pPg->nCell);
  put2byte(&aData[hdr+5], pData - aData);

#ifdef SQLITE_DEBUG
  for(i=0; i<nNew && !CORRUPT_DB; i++){
    u8 *pCell = pCArray->apCell[i+iNew];
    int iOff = get2byteAligned(&pPg->aCellIdx[i*2]);
    if( SQLITE_WITHIN(pCell, aData, &aData[pPg->pBt->usableSize]) ){
      pCell = &pTmp[pCell - aData];
    }
    assert( 0==memcmp(pCell, &aData[iOff],
            pCArray->pRef->xCellSize(pCArray->pRef, pCArray->apCell[i+iNew])) );
  }
#endif

/*
** Make a full copy of pFrom into pTo.  Prior contents of pTo are
** freed before the copy is made.
*/
SQLITE_PRIVATE int sqlite3VdbeMemCopy(Mem *pTo, const Mem *pFrom){
  int rc = SQLITE_OK;





  assert( (pFrom->flags & MEM_RowSet)==0 );
  if( VdbeMemDynamic(pTo) ) vdbeMemClearExternAndSetNull(pTo);
  memcpy(pTo, pFrom, MEMCELLSIZE);
  pTo->flags &= ~MEM_Dyn;
  if( pTo->flags&(MEM_Str|MEM_Blob) ){
    if( 0==(pFrom->flags&MEM_Static) ){
      pTo->flags |= MEM_Ephem;

/*
** Swap all content between two VDBE structures.
*/
SQLITE_PRIVATE void sqlite3VdbeSwap(Vdbe *pA, Vdbe *pB){
  Vdbe tmp, *pTmp;
  char *zTmp;
  assert( pA->db==pB->db );
  tmp = *pA;
  *pA = *pB;
  *pB = tmp;
  pTmp = pA->pNext;
  pA->pNext = pB->pNext;
  pB->pNext = pTmp;
  pTmp = pA->pPrev;

static void vdbeFreeOpArray(sqlite3 *, Op *, int);

/*
** Delete a P4 value if necessary.
*/
static void freeP4(sqlite3 *db, int p4type, void *p4){

  assert( db );
  switch( p4type ){
    case P4_FUNCCTX: {
      freeEphemeralFunction(db, ((sqlite3_context*)p4)->pFunc);
      /* Fall through into the next case */
    }
    case P4_REAL:
    case P4_INT64:
    case P4_DYNAMIC:
    case P4_INTARRAY: {
      sqlite3DbFree(db, p4);
      break;
    }
    case P4_KEYINFO: {
      if( db->pnBytesFreed==0 ) sqlite3KeyInfoUnref((KeyInfo*)p4);
      break;
    }
#ifdef SQLITE_ENABLE_CURSOR_HINTS
    case P4_EXPR: {
      sqlite3ExprDelete(db, (Expr*)p4);
      break;
    }
#endif
    case P4_MPRINTF: {
      if( db->pnBytesFreed==0 ) sqlite3_free(p4);
      break;
    }
    case P4_FUNCDEF: {
      freeEphemeralFunction(db, (FuncDef*)p4);
      break;
    }
    case P4_MEM: {
      if( db->pnBytesFreed==0 ){
        sqlite3ValueFree((sqlite3_value*)p4);
      }else{
        Mem *p = (Mem*)p4;
        if( p->szMalloc ) sqlite3DbFree(db, p->zMalloc);
        sqlite3DbFree(db, p);
      }
      break;
    }
    case P4_VTAB : {
      if( db->pnBytesFreed==0 ) sqlite3VtabUnlock((VTable *)p4);
      break;

    }
  }
}

/*
** Free the space allocated for aOp and any p4 values allocated for the
** opcodes contained within. If aOp is not NULL it is assumed to contain 

    case P4_SUBPROGRAM: {
      sqlite3XPrintf(&x, "program");
      break;
    }
    case P4_ADVANCE: {
      zTemp[0] = 0;
      break;
    }
    case P4_TABLE: {
      sqlite3XPrintf(&x, "%s", pOp->p4.pTab->zName);
      break;
    }
    default: {
      zP4 = pOp->p4.z;
      if( zP4==0 ){
        zP4 = zTemp;
        zTemp[0] = 0;
      }

    u32 serial_type;

    idx += getVarint32(&aKey[idx], serial_type);
    pMem->enc = pKeyInfo->enc;
    pMem->db = pKeyInfo->db;
    /* pMem->flags = 0; // sqlite3VdbeSerialGet() will set this for us */
    pMem->szMalloc = 0;
    pMem->z = 0;
    d += sqlite3VdbeSerialGet(&aKey[d], serial_type, pMem);
    pMem++;
    if( (++u)>=p->nField ) break;
  }
  assert( u<=pKeyInfo->nField + 1 );
  p->nField = u;
}

    p->zErrMsg = sqlite3DbStrDup(db, pVtab->zErrMsg);
    sqlite3_free(pVtab->zErrMsg);
    pVtab->zErrMsg = 0;
  }
}
#endif /* SQLITE_OMIT_VIRTUALTABLE */

#ifdef SQLITE_ENABLE_PREUPDATE_HOOK

/*
** If the second argument is not NULL, release any allocations associated 
** with the memory cells in the p->aMem[] array. Also free the UnpackedRecord
** structure itself, using sqlite3DbFree().
**
** This function is used to free UnpackedRecord structures allocated by
** the vdbeUnpackRecord() function found in vdbeapi.c.
*/
static void vdbeFreeUnpacked(sqlite3 *db, UnpackedRecord *p){
  if( p ){
    int i;
    for(i=0; i<p->nField; i++){
      Mem *pMem = &p->aMem[i];
      if( pMem->zMalloc ) sqlite3VdbeMemRelease(pMem);
    }
    sqlite3DbFree(db, p);
  }
}
#endif /* SQLITE_ENABLE_PREUPDATE_HOOK */

#ifdef SQLITE_ENABLE_PREUPDATE_HOOK
/*
** Invoke the pre-update hook. If this is an UPDATE or DELETE pre-update call,
** then cursor passed as the second argument should point to the row about
** to be update or deleted. If the application calls sqlite3_preupdate_old(),
** the required value will be read from the row the cursor points to.
*/
SQLITE_PRIVATE void sqlite3VdbePreUpdateHook(
  Vdbe *v,                        /* Vdbe pre-update hook is invoked by */
  VdbeCursor *pCsr,               /* Cursor to grab old.* values from */
  int op,                         /* SQLITE_INSERT, UPDATE or DELETE */
  const char *zDb,                /* Database name */
  Table *pTab,                    /* Modified table */
  i64 iKey1,                      /* Initial key value */
  int iReg                        /* Register for new.* record */
){
  sqlite3 *db = v->db;
  i64 iKey2;
  PreUpdate preupdate;
  const char *zTbl = pTab->zName;
  static const u8 fakeSortOrder = 0;

  assert( db->pPreUpdate==0 );
  memset(&preupdate, 0, sizeof(PreUpdate));
  if( op==SQLITE_UPDATE ){
    iKey2 = v->aMem[iReg].u.i;
  }else{
    iKey2 = iKey1;
  }

  assert( pCsr->nField==pTab->nCol 
       || (pCsr->nField==pTab->nCol+1 && op==SQLITE_DELETE && iReg==-1)
  );

  preupdate.v = v;
  preupdate.pCsr = pCsr;
  preupdate.op = op;
  preupdate.iNewReg = iReg;
  preupdate.keyinfo.db = db;
  preupdate.keyinfo.enc = ENC(db);
  preupdate.keyinfo.nField = pTab->nCol;
  preupdate.keyinfo.aSortOrder = (u8*)&fakeSortOrder;
  preupdate.iKey1 = iKey1;
  preupdate.iKey2 = iKey2;
  preupdate.iPKey = pTab->iPKey;

  db->pPreUpdate = &preupdate;
  db->xPreUpdateCallback(db->pPreUpdateArg, db, op, zDb, zTbl, iKey1, iKey2);
  db->pPreUpdate = 0;
  sqlite3DbFree(db, preupdate.aRecord);
  vdbeFreeUnpacked(db, preupdate.pUnpacked);
  vdbeFreeUnpacked(db, preupdate.pNewUnpacked);
  if( preupdate.aNew ){
    int i;
    for(i=0; i<pCsr->nField; i++){
      sqlite3VdbeMemRelease(&preupdate.aNew[i]);
    }
    sqlite3DbFree(db, preupdate.aNew);
  }
}
#endif /* SQLITE_ENABLE_PREUPDATE_HOOK */

/************** End of vdbeaux.c *********************************************/
/************** Begin file vdbeapi.c *****************************************/
/*
** 2004 May 26
**
** The author disclaims copyright to this source code.  In place of
** a legal notice, here is a blessing:

  }
#endif
  v = pVdbe->aCounter[op];
  if( resetFlag ) pVdbe->aCounter[op] = 0;
  return (int)v;
}

#ifdef SQLITE_ENABLE_PREUPDATE_HOOK
/*
** Allocate and populate an UnpackedRecord structure based on the serialized
** record in nKey/pKey. Return a pointer to the new UnpackedRecord structure
** if successful, or a NULL pointer if an OOM error is encountered.
*/
static UnpackedRecord *vdbeUnpackRecord(
  KeyInfo *pKeyInfo, 
  int nKey, 
  const void *pKey
){
  char *dummy;                    /* Dummy argument for AllocUnpackedRecord() */
  UnpackedRecord *pRet;           /* Return value */

  pRet = sqlite3VdbeAllocUnpackedRecord(pKeyInfo, 0, 0, &dummy);
  if( pRet ){
    memset(pRet->aMem, 0, sizeof(Mem)*(pKeyInfo->nField+1));
    sqlite3VdbeRecordUnpack(pKeyInfo, nKey, pKey, pRet);
  }
  return pRet;
}

/*
** This function is called from within a pre-update callback to retrieve
** a field of the row currently being updated or deleted.
*/
SQLITE_API int SQLITE_STDCALL sqlite3_preupdate_old(sqlite3 *db, int iIdx, sqlite3_value **ppValue){
  PreUpdate *p = db->pPreUpdate;
  int rc = SQLITE_OK;

  /* Test that this call is being made from within an SQLITE_DELETE or
  ** SQLITE_UPDATE pre-update callback, and that iIdx is within range. */
  if( !p || p->op==SQLITE_INSERT ){
    rc = SQLITE_MISUSE_BKPT;
    goto preupdate_old_out;
  }
  if( iIdx>=p->pCsr->nField || iIdx<0 ){
    rc = SQLITE_RANGE;
    goto preupdate_old_out;
  }

  /* If the old.* record has not yet been loaded into memory, do so now. */
  if( p->pUnpacked==0 ){
    u32 nRec;
    u8 *aRec;

    rc = sqlite3BtreeDataSize(p->pCsr->uc.pCursor, &nRec);
    if( rc!=SQLITE_OK ) goto preupdate_old_out;
    aRec = sqlite3DbMallocRaw(db, nRec);
    if( !aRec ) goto preupdate_old_out;
    rc = sqlite3BtreeData(p->pCsr->uc.pCursor, 0, nRec, aRec);
    if( rc==SQLITE_OK ){
      p->pUnpacked = vdbeUnpackRecord(&p->keyinfo, nRec, aRec);
      if( !p->pUnpacked ) rc = SQLITE_NOMEM;
    }
    if( rc!=SQLITE_OK ){
      sqlite3DbFree(db, aRec);
      goto preupdate_old_out;
    }
    p->aRecord = aRec;
  }

  if( iIdx>=p->pUnpacked->nField ){
    *ppValue = (sqlite3_value *)columnNullValue();
  }else{
    *ppValue = &p->pUnpacked->aMem[iIdx];
    if( iIdx==p->iPKey ){
      sqlite3VdbeMemSetInt64(*ppValue, p->iKey1);
    }
  }

 preupdate_old_out:
  sqlite3Error(db, rc);
  return sqlite3ApiExit(db, rc);
}
#endif /* SQLITE_ENABLE_PREUPDATE_HOOK */

#ifdef SQLITE_ENABLE_PREUPDATE_HOOK
/*
** This function is called from within a pre-update callback to retrieve
** the number of columns in the row being updated, deleted or inserted.
*/
SQLITE_API int SQLITE_STDCALL sqlite3_preupdate_count(sqlite3 *db){
  PreUpdate *p = db->pPreUpdate;
  return (p ? p->keyinfo.nField : 0);
}
#endif /* SQLITE_ENABLE_PREUPDATE_HOOK */

#ifdef SQLITE_ENABLE_PREUPDATE_HOOK
/*
** This function is designed to be called from within a pre-update callback
** only. It returns zero if the change that caused the callback was made
** immediately by a user SQL statement. Or, if the change was made by a
** trigger program, it returns the number of trigger programs currently
** on the stack (1 for a top-level trigger, 2 for a trigger fired by a 
** top-level trigger etc.).
**
** For the purposes of the previous paragraph, a foreign key CASCADE, SET NULL
** or SET DEFAULT action is considered a trigger.
*/
SQLITE_API int SQLITE_STDCALL sqlite3_preupdate_depth(sqlite3 *db){
  PreUpdate *p = db->pPreUpdate;
  return (p ? p->v->nFrame : 0);
}
#endif /* SQLITE_ENABLE_PREUPDATE_HOOK */

#ifdef SQLITE_ENABLE_PREUPDATE_HOOK
/*
** This function is called from within a pre-update callback to retrieve
** a field of the row currently being updated or inserted.
*/
SQLITE_API int SQLITE_STDCALL sqlite3_preupdate_new(sqlite3 *db, int iIdx, sqlite3_value **ppValue){
  PreUpdate *p = db->pPreUpdate;
  int rc = SQLITE_OK;
  Mem *pMem;

  if( !p || p->op==SQLITE_DELETE ){
    rc = SQLITE_MISUSE_BKPT;
    goto preupdate_new_out;
  }
  if( iIdx>=p->pCsr->nField || iIdx<0 ){
    rc = SQLITE_RANGE;
    goto preupdate_new_out;
  }

  if( p->op==SQLITE_INSERT ){
    /* For an INSERT, memory cell p->iNewReg contains the serialized record
    ** that is being inserted. Deserialize it. */
    UnpackedRecord *pUnpack = p->pNewUnpacked;
    if( !pUnpack ){
      Mem *pData = &p->v->aMem[p->iNewReg];
      rc = sqlite3VdbeMemExpandBlob(pData);
      if( rc!=SQLITE_OK ) goto preupdate_new_out;
      pUnpack = vdbeUnpackRecord(&p->keyinfo, pData->n, pData->z);
      if( !pUnpack ){
        rc = SQLITE_NOMEM;
        goto preupdate_new_out;
      }
      p->pNewUnpacked = pUnpack;
    }
    if( iIdx>=pUnpack->nField ){
      pMem = (sqlite3_value *)columnNullValue();
    }else{
      pMem = &pUnpack->aMem[iIdx];
      if( iIdx==p->iPKey ){
        sqlite3VdbeMemSetInt64(pMem, p->iKey2);
      }
    }
  }else{
    /* For an UPDATE, memory cell (p->iNewReg+1+iIdx) contains the required
    ** value. Make a copy of the cell contents and return a pointer to it.
    ** It is not safe to return a pointer to the memory cell itself as the
    ** caller may modify the value text encoding.
    */
    assert( p->op==SQLITE_UPDATE );
    if( !p->aNew ){
      p->aNew = (Mem *)sqlite3DbMallocZero(db, sizeof(Mem) * p->pCsr->nField);
      if( !p->aNew ){
        rc = SQLITE_NOMEM;
        goto preupdate_new_out;
      }
    }
    assert( iIdx>=0 && iIdx<p->pCsr->nField );
    pMem = &p->aNew[iIdx];
    if( pMem->flags==0 ){
      if( iIdx==p->iPKey ){
        sqlite3VdbeMemSetInt64(pMem, p->iKey2);
      }else{
        rc = sqlite3VdbeMemCopy(pMem, &p->v->aMem[p->iNewReg+1+iIdx]);
        if( rc!=SQLITE_OK ) goto preupdate_new_out;
      }
    }
  }
  *ppValue = pMem;

 preupdate_new_out:
  sqlite3Error(db, rc);
  return sqlite3ApiExit(db, rc);
}
#endif /* SQLITE_ENABLE_PREUPDATE_HOOK */

#ifdef SQLITE_ENABLE_STMT_SCANSTATUS
/*
** Return status data for a single loop within query pStmt.
*/
SQLITE_API int SQLITE_STDCALL sqlite3_stmt_scanstatus(
  sqlite3_stmt *pStmt,            /* Prepared statement being queried */
  int idx,                        /* Index of loop to report on */

static void updateMaxBlobsize(Mem *p){
  if( (p->flags & (MEM_Str|MEM_Blob))!=0 && p->n>sqlite3_max_blobsize ){
    sqlite3_max_blobsize = p->n;
  }
}
#endif

/*
** This macro evaluates to true if either the update hook or the preupdate
** hook are enabled for database connect DB.
*/
#ifdef SQLITE_ENABLE_PREUPDATE_HOOK
# define HAS_UPDATE_HOOK(DB) ((DB)->xPreUpdateCallback||(DB)->xUpdateCallback)
#else
# define HAS_UPDATE_HOOK(DB) ((DB)->xUpdateCallback)
#endif

/*
** The next global variable is incremented each time the OP_Found opcode
** is executed. This is used to test whether or not the foreign key
** operation implemented using OP_FkIsZero is working. This variable
** has no function other than to help verify the correct operation of the
** library.
*/

      }
      break;
    }
  }else{
    /* Neither operand is NULL.  Do a comparison. */
    affinity = pOp->p5 & SQLITE_AFF_MASK;
    if( affinity>=SQLITE_AFF_NUMERIC ){
      if( (flags1 | flags3)&MEM_Str ){
        if( (flags1 & (MEM_Int|MEM_Real|MEM_Str))==MEM_Str ){
          applyNumericAffinity(pIn1,0);
        }
        if( (flags3 & (MEM_Int|MEM_Real|MEM_Str))==MEM_Str ){
          applyNumericAffinity(pIn3,0);
        }
      }
    }else if( affinity==SQLITE_AFF_TEXT ){
      if( (flags1 & MEM_Str)==0 && (flags1 & (MEM_Int|MEM_Real))!=0 ){
        testcase( pIn1->flags & MEM_Int );
        testcase( pIn1->flags & MEM_Real );
        sqlite3VdbeMemStringify(pIn1, encoding, 1);
        testcase( (flags1&MEM_Dyn) != (pIn1->flags&MEM_Dyn) );

        len -= pRec->u.nZero;
      }
    }
    nData += len;
    testcase( serial_type==127 );
    testcase( serial_type==128 );
    nHdr += serial_type<=127 ? 1 : sqlite3VarintLen(serial_type);
    if( pRec==pData0 ) break;
    pRec--;
  }while(1);

  /* EVIDENCE-OF: R-22564-11647 The header begins with a single varint
  ** which determines the total number of bytes in the header. The varint
  ** value is the size of the header in bytes including the size varint
  ** itself. */
  testcase( nHdr==126 );
  testcase( nHdr==127 );

        ** "transaction savepoint". */
        if( db->autoCommit ){
          db->autoCommit = 0;
          db->isTransactionSavepoint = 1;
        }else{
          db->nSavepoint++;
        }

        /* Link the new savepoint into the database handle's list. */
        pNew->pNext = db->pSavepoint;
        db->pSavepoint = pNew;
        pNew->nDeferredCons = db->nDeferredCons;
        pNew->nDeferredImmCons = db->nDeferredImmCons;
      }
    }

** that boosts performance by avoiding redundant seeks.
**
** If the OPFLAG_ISUPDATE flag is set, then this opcode is part of an
** UPDATE operation.  Otherwise (if the flag is clear) then this opcode
** is part of an INSERT operation.  The difference is only important to
** the update hook.
**
** Parameter P4 may point to a Table structure, or may be NULL. If it is 
** not NULL, then the update-hook (sqlite3.xUpdateCallback) is invoked 
** following a successful insert.
**
** (WARNING/TODO: If P1 is a pseudo-cursor and P2 is dynamically
** allocated, then ownership of P2 is transferred to the pseudo-cursor
** and register P2 becomes ephemeral.  If the cursor is changed, the
** value of register P2 will then change.  Make sure this does not
** cause any problems.)
**

  Mem *pData;       /* MEM cell holding data for the record to be inserted */
  Mem *pKey;        /* MEM cell holding key  for the record */
  i64 iKey;         /* The integer ROWID or key for the record to be inserted */
  VdbeCursor *pC;   /* Cursor to table into which insert is written */
  int nZero;        /* Number of zero-bytes to append */
  int seekResult;   /* Result of prior seek or 0 if no USESEEKRESULT flag */
  const char *zDb;  /* database name - used by the update hook */
  Table *pTab;      /* Table structure - used by update and pre-update hooks */
  int op;           /* Opcode for update hook: SQLITE_UPDATE or SQLITE_INSERT */

  op = 0;
  pData = &aMem[pOp->p2];
  assert( pOp->p1>=0 && pOp->p1<p->nCursor );
  assert( memIsValid(pData) );
  pC = p->apCsr[pOp->p1];
  assert( pC!=0 );
  assert( pC->eCurType==CURTYPE_BTREE );
  assert( pC->uc.pCursor!=0 );
  assert( pC->isTable );
  assert( pOp->p4type==P4_TABLE || pOp->p4type>=P4_STATIC );
  REGISTER_TRACE(pOp->p2, pData);

  if( pOp->opcode==OP_Insert ){
    pKey = &aMem[pOp->p3];
    assert( pKey->flags & MEM_Int );
    assert( memIsValid(pKey) );
    REGISTER_TRACE(pOp->p3, pKey);
    iKey = pKey->u.i;
  }else{
    assert( pOp->opcode==OP_InsertInt );
    iKey = pOp->p3;
  }

  if( pOp->p4type==P4_TABLE && HAS_UPDATE_HOOK(db) ){
    assert( pC->isTable );
    assert( pC->iDb>=0 );
    zDb = db->aDb[pC->iDb].zName;
    pTab = pOp->p4.pTab;
    assert( HasRowid(pTab) );
    op = ((pOp->p5 & OPFLAG_ISUPDATE) ? SQLITE_UPDATE : SQLITE_INSERT);
  }else{
    pTab = 0; /* Not needed.  Silence a comiler warning. */
    zDb = 0;  /* Not needed.  Silence a compiler warning. */
  }

#ifdef SQLITE_ENABLE_PREUPDATE_HOOK
  /* Invoke the pre-update hook, if any */
  if( db->xPreUpdateCallback 
   && pOp->p4type==P4_TABLE
   && !(pOp->p5 & OPFLAG_ISUPDATE)
  ){
    sqlite3VdbePreUpdateHook(p, pC, SQLITE_INSERT, zDb, pTab, iKey, pOp->p2);
  }
#endif

  if( pOp->p5 & OPFLAG_NCHANGE ) p->nChange++;
  if( pOp->p5 & OPFLAG_LASTROWID ) db->lastRowid = lastRowid = iKey;
  if( pData->flags & MEM_Null ){
    pData->z = 0;
    pData->n = 0;
  }else{

                          (pOp->p5 & OPFLAG_APPEND)!=0, seekResult
  );
  pC->deferredMoveto = 0;
  pC->cacheStatus = CACHE_STALE;

  /* Invoke the update-hook if required. */
  if( rc ) goto abort_due_to_error;
  if( db->xUpdateCallback && op ){




    db->xUpdateCallback(db->pUpdateArg, op, zDb, pTab->zName, iKey);

  }
  break;
}

/* Opcode: Delete P1 P2 P3 P4 P5
**
** Delete the record at which the P1 cursor is currently pointing.
**
** If the OPFLAG_SAVEPOSITION bit of the P5 parameter is set, then
** the cursor will be left pointing at  either the next or the previous
** record in the table. If it is left pointing at the next record, then
** the next Next instruction will be a no-op. As a result, in this case

**
** If the OPFLAG_NCHANGE flag of P2 (NB: P2 not P5) is set, then the row
** change count is incremented (otherwise not).
**
** P1 must not be pseudo-table.  It has to be a real table with
** multiple rows.
**
** If P4 is not NULL then it points to a Table struture. In this case either 

** the update or pre-update hook, or both, may be invoked. The P1 cursor must
** have been positioned using OP_NotFound prior to invoking this opcode in 
** this case. Specifically, if one is configured, the pre-update hook is 
** invoked if P4 is not NULL. The update-hook is invoked if one is configured, 
** P4 is not NULL, and the OPFLAG_NCHANGE flag is set in P2.
**
** If the OPFLAG_ISUPDATE flag is set in P2, then P3 contains the address
** of the memory cell that contains the value that the rowid of the row will
** be set to by the update.
*/
case OP_Delete: {
  VdbeCursor *pC;
  const char *zDb;
  Table *pTab;
  int opflags;

  opflags = pOp->p2;
  assert( pOp->p1>=0 && pOp->p1<p->nCursor );
  pC = p->apCsr[pOp->p1];
  assert( pC!=0 );
  assert( pC->eCurType==CURTYPE_BTREE );
  assert( pC->uc.pCursor!=0 );
  assert( pC->deferredMoveto==0 );






#ifdef SQLITE_DEBUG
  if( pOp->p4type==P4_TABLE && HasRowid(pOp->p4.pTab) && pOp->p5==0 ){
    /* If p5 is zero, the seek operation that positioned the cursor prior to
    ** OP_Delete will have also set the pC->movetoTarget field to the rowid of
    ** the row that is being deleted */

    i64 iKey = 0;
    sqlite3BtreeKeySize(pC->uc.pCursor, &iKey);
    assert( pC->movetoTarget==iKey );
  }
#endif

  /* If the update-hook or pre-update-hook will be invoked, set zDb to
  ** the name of the db to pass as to it. Also set local pTab to a copy
  ** of p4.pTab. Finally, if p5 is true, indicating that this cursor was
  ** last moved with OP_Next or OP_Prev, not Seek or NotFound, set 
  ** VdbeCursor.movetoTarget to the current rowid.  */
  if( pOp->p4type==P4_TABLE && HAS_UPDATE_HOOK(db) ){
    assert( pC->iDb>=0 );
    assert( pOp->p4.pTab!=0 );
    zDb = db->aDb[pC->iDb].zName;
    pTab = pOp->p4.pTab;
    if( (pOp->p5 & OPFLAG_SAVEPOSITION)!=0 && pC->isTable ){
      sqlite3BtreeKeySize(pC->uc.pCursor, &pC->movetoTarget);
    }
  }else{
    zDb = 0;   /* Not needed.  Silence a compiler warning. */
    pTab = 0;  /* Not needed.  Silence a compiler warning. */
  }

#ifdef SQLITE_ENABLE_PREUPDATE_HOOK
  /* Invoke the pre-update-hook if required. */
  if( db->xPreUpdateCallback && pOp->p4.pTab && HasRowid(pTab) ){
    assert( !(opflags & OPFLAG_ISUPDATE) || (aMem[pOp->p3].flags & MEM_Int) );
    sqlite3VdbePreUpdateHook(p, pC,
        (opflags & OPFLAG_ISUPDATE) ? SQLITE_UPDATE : SQLITE_DELETE, 
        zDb, pTab, pC->movetoTarget,
        pOp->p3
    );
  }
  if( opflags & OPFLAG_ISNOOP ) break;
#endif
 
  /* Only flags that can be set are SAVEPOISTION and AUXDELETE */ 
  assert( (pOp->p5 & ~(OPFLAG_SAVEPOSITION|OPFLAG_AUXDELETE))==0 );
  assert( OPFLAG_SAVEPOSITION==BTREE_SAVEPOSITION );
  assert( OPFLAG_AUXDELETE==BTREE_AUXDELETE );

#ifdef SQLITE_DEBUG
  if( p->pFrame==0 ){

      nExtraDelete--;
    }
  }
#endif

  rc = sqlite3BtreeDelete(pC->uc.pCursor, pOp->p5);
  pC->cacheStatus = CACHE_STALE;
  if( rc ) goto abort_due_to_error;

  /* Invoke the update-hook if required. */
  if( opflags & OPFLAG_NCHANGE ){
    p->nChange++;
    if( db->xUpdateCallback && HasRowid(pTab) ){
      db->xUpdateCallback(db->pUpdateArg, SQLITE_DELETE, zDb, pTab->zName,
          pC->movetoTarget);
      assert( pC->iDb>=0 );
    }
  }

  break;
}
/* Opcode: ResetCount * * * * *
**
** The value of the change counter is copied to the database handle
** change counter (returned by subsequent calls to sqlite3_changes()).
** Then the VMs internal change counter resets to 0.

  int flags;              /* Copy of "flags" passed to sqlite3_blob_open() */
  int nByte;              /* Size of open blob, in bytes */
  int iOffset;            /* Byte offset of blob in cursor data */
  int iCol;               /* Table column this handle is open on */
  BtCursor *pCsr;         /* Cursor pointing at blob row */
  sqlite3_stmt *pStmt;    /* Statement holding cursor open */
  sqlite3 *db;            /* The associated database */
  char *zDb;              /* Database name */
  Table *pTab;            /* Table object */
};


/*
** This function is used by both blob_open() and blob_reopen(). It seeks
** the b-tree cursor associated with blob handle p to point to row iRow.
** If successful, SQLITE_OK is returned and subsequent calls to

        zErr = pParse->zErrMsg;
        pParse->zErrMsg = 0;
      }
      rc = SQLITE_ERROR;
      sqlite3BtreeLeaveAll(db);
      goto blob_open_out;
    }
    pBlob->pTab = pTab;
    pBlob->zDb = db->aDb[sqlite3SchemaToIndex(db, pTab->pSchema)].zName;

    /* Now search pTab for the exact column. */
    for(iCol=0; iCol<pTab->nCol; iCol++) {
      if( sqlite3StrICmp(pTab->aCol[iCol].zName, zColumn)==0 ){
        break;
      }
    }

    rc = SQLITE_ABORT;
  }else{
    /* Call either BtreeData() or BtreePutData(). If SQLITE_ABORT is
    ** returned, clean-up the statement handle.
    */
    assert( db == v->db );
    sqlite3BtreeEnterCursor(p->pCsr);

#ifdef SQLITE_ENABLE_PREUPDATE_HOOK
    if( xCall==sqlite3BtreePutData && db->xPreUpdateCallback ){
      /* If a pre-update hook is registered and this is a write cursor, 
      ** invoke it here. 
      ** 
      ** TODO: The preupdate-hook is passed SQLITE_DELETE, even though this
      ** operation should really be an SQLITE_UPDATE. This is probably
      ** incorrect, but is convenient because at this point the new.* values 
      ** are not easily obtainable. And for the sessions module, an 
      ** SQLITE_UPDATE where the PK columns do not change is handled in the 
      ** same way as an SQLITE_DELETE (the SQLITE_DELETE code is actually
      ** slightly more efficient). Since you cannot write to a PK column
      ** using the incremental-blob API, this works. For the sessions module
      ** anyhow.
      */
      sqlite3_int64 iKey;
      sqlite3BtreeKeySize(p->pCsr, &iKey);
      sqlite3VdbePreUpdateHook(
          v, v->apCsr[0], SQLITE_DELETE, p->zDb, p->pTab, iKey, -1
      );
    }
#endif

    rc = xCall(p->pCsr, iOffset+p->iOffset, n, z);
    sqlite3BtreeLeaveCursor(p->pCsr);
    if( rc==SQLITE_ABORT ){
      sqlite3VdbeFinalize(v);
      p->pStmt = 0;
    }else{
      v->rc = rc;

#ifdef SQLITE_ENABLE_ATOMIC_WRITE
  if( (iAmt+iOfst)>p->endpoint.iOffset ){
    return SQLITE_IOERR_SHORT_READ;
  }
#endif

  assert( (iAmt+iOfst)<=p->endpoint.iOffset );
  assert( p->readpoint.iOffset==0 || p->readpoint.pChunk!=0 );
  if( p->readpoint.iOffset!=iOfst || iOfst==0 ){
    sqlite3_int64 iOff = 0;
    for(pChunk=p->pFirst; 
        ALWAYS(pChunk) && (iOff+p->nChunkSize)<=iOfst;
        pChunk=pChunk->pNext
    ){
      iOff += p->nChunkSize;
    }
  }else{
    pChunk = p->readpoint.pChunk;
    assert( pChunk!=0 );
  }

  iChunkOffset = (int)(iOfst%p->nChunkSize);
  do {
    int iSpace = p->nChunkSize - iChunkOffset;
    int nCopy = MIN(nRead, (p->nChunkSize - iChunkOffset));
    memcpy(zOut, (u8*)pChunk->zChunk + iChunkOffset, nCopy);
    zOut += nCopy;
    nRead -= iSpace;
    iChunkOffset = 0;
  } while( nRead>=0 && (pChunk=pChunk->pNext)!=0 && nRead>0 );
  p->readpoint.iOffset = pChunk ? iOfst+iAmt : 0;
  p->readpoint.pChunk = pChunk;

  return SQLITE_OK;
}

/*
** Free the list of FileChunk structures headed at MemJournal.pFirst.

** This means if the caller does not care about other errors, the return
** code may be ignored.
*/
SQLITE_PRIVATE int sqlite3AnalysisLoad(sqlite3 *db, int iDb){
  analysisInfo sInfo;
  HashElem *i;
  char *zSql;
  int rc = SQLITE_OK;

  assert( iDb>=0 && iDb<db->nDb );
  assert( db->aDb[iDb].pBt!=0 );

  /* Clear any prior statistics */
  assert( sqlite3SchemaMutexHeld(db, iDb, 0) );
  for(i=sqliteHashFirst(&db->aDb[iDb].pSchema->idxHash);i;i=sqliteHashNext(i)){
    Index *pIdx = sqliteHashData(i);
    pIdx->aiRowLogEst[0] = 0;
#ifdef SQLITE_ENABLE_STAT3_OR_STAT4
    sqlite3DeleteIndexSamples(db, pIdx);
    pIdx->aSample = 0;
#endif
  }

  /* Load new statistics out of the sqlite_stat1 table */
  sInfo.db = db;
  sInfo.zDatabase = db->aDb[iDb].zName;
  if( sqlite3FindTable(db, "sqlite_stat1", sInfo.zDatabase)!=0 ){




    zSql = sqlite3MPrintf(db, 
        "SELECT tbl,idx,stat FROM %Q.sqlite_stat1", sInfo.zDatabase);
    if( zSql==0 ){
      rc = SQLITE_NOMEM_BKPT;
    }else{
      rc = sqlite3_exec(db, zSql, analysisLoader, &sInfo, 0);
      sqlite3DbFree(db, zSql);
    }
  }

  /* Set appropriate defaults on all indexes not in the sqlite_stat1 table */
  assert( sqlite3SchemaMutexHeld(db, iDb, 0) );
  for(i=sqliteHashFirst(&db->aDb[iDb].pSchema->idxHash);i;i=sqliteHashNext(i)){
    Index *pIdx = sqliteHashData(i);
    if( pIdx->aiRowLogEst[0]==0 ) sqlite3DefaultRowEst(pIdx);
  }

  /* Load the statistics from the sqlite_stat4 table. */
#ifdef SQLITE_ENABLE_STAT3_OR_STAT4
  if( rc==SQLITE_OK && OptimizationEnabled(db, SQLITE_Stat34) ){
    db->lookaside.bDisable++;
    rc = loadStat4(db, sInfo.zDatabase);
    db->lookaside.bDisable--;

  ** Note that the call to sqlite3ResultSetOfSelect() will expand any
  ** "*" elements in the results set of the view and will assign cursors
  ** to the elements of the FROM clause.  But we do not want these changes
  ** to be permanent.  So the computation is done on a copy of the SELECT
  ** statement that defines the view.
  */
  assert( pTable->pSelect );






  pSel = sqlite3SelectDup(db, pTable->pSelect, 0);
  if( pSel ){
    n = pParse->nTab;
    sqlite3SrcListAssignCursors(pParse, pSel->pSrc);
    pTable->nCol = -1;
    db->lookaside.bDisable++;
#ifndef SQLITE_OMIT_AUTHORIZATION
    xAuth = db->xAuth;
    db->xAuth = 0;
    pSelTab = sqlite3ResultSetOfSelect(pParse, pSel);
    db->xAuth = xAuth;
#else
    pSelTab = sqlite3ResultSetOfSelect(pParse, pSel);
#endif

    pParse->nTab = n;
    if( pTable->pCheck ){
      /* CREATE VIEW name(arglist) AS ...
      ** The names of the columns in the table are taken from
      ** arglist which is stored in pTable->pCheck.  The pCheck field
      ** normally holds CHECK constraints on an ordinary table, but for
      ** a VIEW it holds the list of column names.
      */
      sqlite3ColumnsFromExprList(pParse, pTable->pCheck, 
                                 &pTable->nCol, &pTable->aCol);
      if( db->mallocFailed==0 
       && pParse->nErr==0
       && pTable->nCol==pSel->pEList->nExpr
      ){
        sqlite3SelectAddColumnTypeAndCollation(pParse, pTable, pSel);
      }
    }else if( pSelTab ){
      /* CREATE VIEW name AS...  without an argument list.  Construct
      ** the column names from the SELECT statement that defines the view.
      */
      assert( pTable->aCol==0 );
      pTable->nCol = pSelTab->nCol;
      pTable->aCol = pSelTab->aCol;
      pSelTab->nCol = 0;
      pSelTab->aCol = 0;

      assert( sqlite3SchemaMutexHeld(db, 0, pTable->pSchema) );
    }else{
      pTable->nCol = 0;
      nErr++;
    }
    if( pSelTab ) sqlite3DeleteTable(db, pSelTab);
    sqlite3SelectDelete(db, pSel);
    db->lookaside.bDisable--;
  } else {
    nErr++;

  }
  pTable->pSchema->schemaFlags |= DB_UnresetViews;
#endif /* SQLITE_OMIT_VIEW */
  return nErr;  
}
#endif /* !defined(SQLITE_OMIT_VIEW) || !defined(SQLITE_OMIT_VIRTUALTABLE) */

  if( v==0 ) return;
  if( memRootPage>=0 ){
    tnum = memRootPage;
  }else{
    tnum = pIndex->tnum;
  }
  pKey = sqlite3KeyInfoOfIndex(pParse, pIndex);
  assert( pKey!=0 || db->mallocFailed || pParse->nErr );

  /* Open the sorter cursor if we are to use one. */
  iSorter = pParse->nTab++;
  sqlite3VdbeAddOp4(v, OP_SorterOpen, iSorter, 0, pIndex->nKeyCol, (char*)
                    sqlite3KeyInfoRef(pKey), P4_KEYINFO);

  /* Open the table. Loop through all rows of the table, inserting index

  sqlite3VdbeJumpHere(v, addr1);
  if( memRootPage<0 ) sqlite3VdbeAddOp2(v, OP_Clear, tnum, iDb);
  sqlite3VdbeAddOp4(v, OP_OpenWrite, iIdx, tnum, iDb, 
                    (char *)pKey, P4_KEYINFO);
  sqlite3VdbeChangeP5(v, OPFLAG_BULKCSR|((memRootPage>=0)?OPFLAG_P2ISREG:0));

  addr1 = sqlite3VdbeAddOp2(v, OP_SorterSort, iSorter, 0); VdbeCoverage(v);

  if( IsUniqueIndex(pIndex) ){
    int j2 = sqlite3VdbeCurrentAddr(v) + 3;
    sqlite3VdbeGoto(v, j2);
    addr2 = sqlite3VdbeCurrentAddr(v);
    sqlite3VdbeAddOp4Int(v, OP_SorterCompare, iSorter, j2, regRecord,
                         pIndex->nKeyCol); VdbeCoverage(v);
    sqlite3UniqueConstraint(pParse, OE_Abort, pIndex);
  }else{

  ** It is easier just to erase the whole table. Prior to version 3.6.5,
  ** this optimization caused the row change count (the value returned by 
  ** API function sqlite3_count_changes) to be set incorrectly.  */
  if( rcauth==SQLITE_OK
   && pWhere==0
   && !bComplex
   && !IsVirtual(pTab)
#ifdef SQLITE_ENABLE_PREUPDATE_HOOK
   && db->xPreUpdateCallback==0
#endif
  ){
    assert( !isView );
    sqlite3TableLock(pParse, iDb, pTab->tnum, 1, pTab->zName);
    if( HasRowid(pTab) ){
      sqlite3VdbeAddOp4(v, OP_Clear, pTab->tnum, iDb, memCnt,
                        pTab->zName, P4_STATIC);
    }

    ** refer to this table (i.e. constraints attached to other tables) 
    ** are not violated by deleting this row.  */
    sqlite3FkCheck(pParse, pTab, iOld, 0, 0, 0);
  }

  /* Delete the index and table entries. Skip this step if pTab is really
  ** a view (in which case the only effect of the DELETE statement is to
  ** fire the INSTEAD OF triggers).  
  **
  ** If variable 'count' is non-zero, then this OP_Delete instruction should
  ** invoke the update-hook. The pre-update-hook, on the other hand should
  ** be invoked unless table pTab is a system table. The difference is that
  ** the update-hook is not invoked for rows removed by REPLACE, but the 
  ** pre-update-hook is.
  */ 
  if( pTab->pSelect==0 ){
    u8 p5 = 0;
    sqlite3GenerateRowIndexDelete(pParse, pTab, iDataCur, iIdxCur,0,iIdxNoSeek);
    sqlite3VdbeAddOp2(v, OP_Delete, iDataCur, (count?OPFLAG_NCHANGE:0));

    sqlite3VdbeChangeP4(v, -1, (char*)pTab, P4_TABLE);

    if( eMode!=ONEPASS_OFF ){
      sqlite3VdbeChangeP5(v, OPFLAG_AUXDELETE);
    }
    if( iIdxNoSeek>=0 ){
      sqlite3VdbeAddOp1(v, OP_Delete, iIdxNoSeek);
    }
    if( eMode==ONEPASS_MULTI ) p5 |= OPFLAG_SAVEPOSITION;

  Trigger *pTrigger;              /* Trigger definition to return */
  int iAction = (pChanges!=0);    /* 1 for UPDATE, 0 for DELETE */

  action = pFKey->aAction[iAction];
  if( action==OE_Restrict && (db->flags & SQLITE_DeferFKs) ){
    return 0;
  }

  pTrigger = pFKey->apTrigger[iAction];

  if( action!=OE_None && !pTrigger ){
    char const *zFrom;            /* Name of child table */
    int nFrom;                    /* Length in bytes of zFrom */
    Index *pIdx = 0;              /* Parent key index for this FK */
    int *aiCol = 0;               /* child table cols -> parent key cols */

        Trigger *pTrigger = 0;
        if( db->flags&SQLITE_RecTriggers ){
          pTrigger = sqlite3TriggersExist(pParse, pTab, TK_DELETE, 0, 0);
        }
        if( pTrigger || sqlite3FkRequired(pParse, pTab, 0, 0) ){
          sqlite3MultiWrite(pParse);
          sqlite3GenerateRowDelete(pParse, pTab, pTrigger, iDataCur, iIdxCur,
                                   regNewData, 1, 0, OE_Replace, 1, -1);

        }else{
#ifdef SQLITE_ENABLE_PREUPDATE_HOOK
          if( HasRowid(pTab) ){
            /* This OP_Delete opcode fires the pre-update-hook only. It does
            ** not modify the b-tree. It is more efficient to let the coming
            ** OP_Insert replace the existing entry than it is to delete the
            ** existing entry and then insert a new one. */
            sqlite3VdbeAddOp2(v, OP_Delete, iDataCur, OPFLAG_ISNOOP);
            sqlite3VdbeChangeP4(v, -1, (char *)pTab, P4_TABLE);
          }
#endif /* SQLITE_ENABLE_PREUPDATE_HOOK */
          if( pTab->pIndex ){
            sqlite3MultiWrite(pParse);
            sqlite3GenerateRowIndexDelete(pParse, pTab, iDataCur, iIdxCur,0,-1);
          }
        }
        seenReplace = 1;
        break;

    pik_flags |= OPFLAG_APPEND;
  }
  if( useSeekResult ){
    pik_flags |= OPFLAG_USESEEKRESULT;
  }
  sqlite3VdbeAddOp3(v, OP_Insert, iDataCur, regRec, regNewData);
  if( !pParse->nested ){
    sqlite3VdbeChangeP4(v, -1, (char *)pTab, P4_TABLE);
  }
  sqlite3VdbeChangeP5(v, pik_flags);
}

/*
** Allocate cursors for the pTab table and all its indices and generate
** code to open and initialized those cursors.

      addr1 = sqlite3VdbeAddOp2(v, OP_NewRowid, iDest, regRowid);
    }else{
      addr1 = sqlite3VdbeAddOp2(v, OP_Rowid, iSrc, regRowid);
      assert( (pDest->tabFlags & TF_Autoincrement)==0 );
    }
    sqlite3VdbeAddOp2(v, OP_RowData, iSrc, regData);
    sqlite3VdbeAddOp4(v, OP_Insert, iDest, regData, regRowid,
                      (char*)pDest, P4_TABLE);
    sqlite3VdbeChangeP5(v, OPFLAG_NCHANGE|OPFLAG_LASTROWID|OPFLAG_APPEND);
    sqlite3VdbeAddOp2(v, OP_Next, iSrc, addr1); VdbeCoverage(v);
    sqlite3VdbeAddOp2(v, OP_Close, iSrc, 0);
    sqlite3VdbeAddOp2(v, OP_Close, iDest, 0);
  }else{
    sqlite3TableLock(pParse, iDbDest, pDest->tnum, 1, pDest->zName);
    sqlite3TableLock(pParse, iDbSrc, pSrc->tnum, 0, pSrc->zName);

** The column list presumably came from selectColumnNamesFromExprList().
** The column list has only names, not types or collations.  This
** routine goes through and adds the types and collations.
**
** This routine requires that all identifiers in the SELECT
** statement be resolved.
*/
SQLITE_PRIVATE void sqlite3SelectAddColumnTypeAndCollation(
  Parse *pParse,        /* Parsing contexts */
  Table *pTab,          /* Add column type information to this table */
  Select *pSelect       /* SELECT used to determine types and collations */
){
  sqlite3 *db = pParse->db;
  NameContext sNC;
  Column *pCol;

  assert( (pSelect->selFlags & SF_Resolved)!=0 );
  assert( pTab->nCol==pSelect->pEList->nExpr || db->mallocFailed );
  if( db->mallocFailed ) return;
  memset(&sNC, 0, sizeof(sNC));
  sNC.pSrcList = pSelect->pSrc;
  a = pSelect->pEList->a;
  for(i=0, pCol=pTab->aCol; i<pTab->nCol; i++, pCol++){
    const char *zType;
    int n, m;
    p = a[i].pExpr;
    zType = columnType(&sNC, p, 0, 0, 0, &pCol->szEst);
    szAll += pCol->szEst;
    pCol->affinity = sqlite3ExprAffinity(p);
    if( zType && (m = sqlite3Strlen30(zType))>0 ){
      n = sqlite3Strlen30(pCol->zName);
      pCol->zName = sqlite3DbReallocOrFree(db, pCol->zName, n+m+2);
      if( pCol->zName ){
        memcpy(&pCol->zName[n+1], zType, m+1);
        pCol->colFlags |= COLFLAG_HASTYPE;
      }
    }
    if( pCol->affinity==0 ) pCol->affinity = SQLITE_AFF_BLOB;
    pColl = sqlite3ExprCollSeq(pParse, p);
    if( pColl && pCol->zColl==0 ){
      pCol->zColl = sqlite3DbStrDup(db, pColl->zName);
    }
  }
  pTab->szTabRow = sqlite3LogEst(szAll*4);

  /* The sqlite3ResultSetOfSelect() is only used n contexts where lookaside
  ** is disabled */
  assert( db->lookaside.bDisable );
  pTab->nRef = 1;
  pTab->zName = 0;
  pTab->nRowLogEst = 200; assert( 200==sqlite3LogEst(1048576) );
  sqlite3ColumnsFromExprList(pParse, pSelect->pEList, &pTab->nCol, &pTab->aCol);
  sqlite3SelectAddColumnTypeAndCollation(pParse, pTab, pSelect);
  pTab->iPKey = -1;
  if( db->mallocFailed ){
    sqlite3DeleteTable(db, pTab);
    return 0;
  }
  return pTab;
}

    Table *pTab = pFrom->pTab;
    assert( pTab!=0 );
    if( (pTab->tabFlags & TF_Ephemeral)!=0 ){
      /* A sub-query in the FROM clause of a SELECT */
      Select *pSel = pFrom->pSelect;
      if( pSel ){
        while( pSel->pPrior ) pSel = pSel->pPrior;
        sqlite3SelectAddColumnTypeAndCollation(pParse, pTab, pSel);
      }
    }
  }
}
#endif

        addr1 = sqlite3VdbeAddOp4Int(v, OP_NotFound, iDataCur, 0, regKey, nKey);
      }else{
        addr1 = sqlite3VdbeAddOp3(v, OP_NotExists, iDataCur, 0, regOldRowid);
      }
      VdbeCoverageNeverTaken(v);
    }
    sqlite3GenerateRowIndexDelete(pParse, pTab, iDataCur, iIdxCur, aRegIdx, -1);

    /* If changing the rowid value, or if there are foreign key constraints
    ** to process, delete the old record. Otherwise, add a noop OP_Delete
    ** to invoke the pre-update hook.
    **
    ** That (regNew==regnewRowid+1) is true is also important for the 
    ** pre-update hook. If the caller invokes preupdate_new(), the returned
    ** value is copied from memory cell (regNewRowid+1+iCol), where iCol
    ** is the column index supplied by the user.
    */
    assert( regNew==regNewRowid+1 );
#ifdef SQLITE_ENABLE_PREUPDATE_HOOK
    sqlite3VdbeAddOp3(v, OP_Delete, iDataCur,
        OPFLAG_ISUPDATE | ((hasFK || chngKey || pPk!=0) ? 0 : OPFLAG_ISNOOP),
        regNewRowid
    );
    if( !pParse->nested ){
      sqlite3VdbeChangeP4(v, -1, (char*)pTab, P4_TABLE);
    }
#else
    if( hasFK || chngKey || pPk!=0 ){
      sqlite3VdbeAddOp2(v, OP_Delete, iDataCur, 0);
    }
#endif
    if( bReplace || chngKey ){
      sqlite3VdbeJumpHere(v, addr1);
    }

    if( hasFK ){
      sqlite3FkCheck(pParse, pTab, 0, regNewRowid, aXRef, chngKey);
    }

  pNew = pBuilder->pNew;
  if( db->mallocFailed ) return SQLITE_NOMEM_BKPT;

  assert( (pNew->wsFlags & WHERE_VIRTUALTABLE)==0 );
  assert( (pNew->wsFlags & WHERE_TOP_LIMIT)==0 );
  if( pNew->wsFlags & WHERE_BTM_LIMIT ){
    opMask = WO_LT|WO_LE;


  }else{
    opMask = WO_EQ|WO_IN|WO_GT|WO_GE|WO_LT|WO_LE|WO_ISNULL|WO_IS;
  }
  if( pProbe->bUnordered ) opMask &= ~(WO_GT|WO_GE|WO_LT|WO_LE);

  assert( pNew->u.btree.nEq<pProbe->nColumn );

      continue; /* ignore IS [NOT] NULL constraints on NOT NULL columns */
    }
    if( pTerm->prereqRight & pNew->maskSelf ) continue;

    /* Do not allow the upper bound of a LIKE optimization range constraint
    ** to mix with a lower range bound from some other source */
    if( pTerm->wtFlags & TERM_LIKEOPT && pTerm->eOperator==WO_LT ) continue;

    /* Do not allow IS constraints from the WHERE clause to be used by the
    ** right table of a LEFT JOIN.  Only constraints in the ON clause are
    ** allowed */
    if( (pSrc->fg.jointype & JT_LEFT)!=0
     && !ExprHasProperty(pTerm->pExpr, EP_FromJoin)
     && (eOp & (WO_IS|WO_ISNULL))!=0
    ){
      testcase( eOp & WO_IS );
      testcase( eOp & WO_ISNULL );
      continue;
    }

    pNew->wsFlags = saved_wsFlags;
    pNew->u.btree.nEq = saved_nEq;
    pNew->nLTerm = saved_nLTerm;
    if( whereLoopResize(db, pNew, pNew->nLTerm+1) ) break; /* OOM */
    pNew->aLTerm[pNew->nLTerm++] = pTerm;
    pNew->prereq = (saved_prereq | pTerm->prereqRight) & ~pNew->maskSelf;

  pRet = db->pRollbackArg;
  db->xRollbackCallback = xCallback;
  db->pRollbackArg = pArg;
  sqlite3_mutex_leave(db->mutex);
  return pRet;
}

#ifdef SQLITE_ENABLE_PREUPDATE_HOOK
/*
** Register a callback to be invoked each time a row is updated,
** inserted or deleted using this database connection.
*/
SQLITE_API void *SQLITE_STDCALL sqlite3_preupdate_hook(
  sqlite3 *db,              /* Attach the hook to this database */
  void(*xCallback)(         /* Callback function */
    void*,sqlite3*,int,char const*,char const*,sqlite3_int64,sqlite3_int64),
  void *pArg                /* First callback argument */
){
  void *pRet;
  sqlite3_mutex_enter(db->mutex);
  pRet = db->pPreUpdateArg;
  db->xPreUpdateCallback = xCallback;
  db->pPreUpdateArg = pArg;
  sqlite3_mutex_leave(db->mutex);
  return pRet;
}
#endif /* SQLITE_ENABLE_PREUPDATE_HOOK */

#ifndef SQLITE_OMIT_WAL
/*
** The sqlite3_wal_hook() callback registered by sqlite3_wal_autocheckpoint().
** Invoke sqlite3_wal_checkpoint if the number of frames in the log file
** is greater than sqlite3.pWalArg cast to an integer (the value configured by
** wal_autocheckpoint()).
*/ 

  return sqlite3_create_module(db, "dbstat", &dbstat_module, 0);
}
#elif defined(SQLITE_ENABLE_DBSTAT_VTAB)
SQLITE_PRIVATE int sqlite3DbstatRegister(sqlite3 *db){ return SQLITE_OK; }
#endif /* SQLITE_ENABLE_DBSTAT_VTAB */

/************** End of dbstat.c **********************************************/
/************** Begin file sqlite3session.c **********************************/

#if defined(SQLITE_ENABLE_SESSION) && defined(SQLITE_ENABLE_PREUPDATE_HOOK)
/* #include "sqlite3session.h" */
/* #include <assert.h> */
/* #include <string.h> */

#ifndef SQLITE_AMALGAMATION
/* # include "sqliteInt.h" */
/* # include "vdbeInt.h" */
#endif

typedef struct SessionTable SessionTable;
typedef struct SessionChange SessionChange;
typedef struct SessionBuffer SessionBuffer;
typedef struct SessionInput SessionInput;

/*
** Minimum chunk size used by streaming versions of functions.
*/
#ifndef SESSIONS_STRM_CHUNK_SIZE
# ifdef SQLITE_TEST
#   define SESSIONS_STRM_CHUNK_SIZE 64
# else
#   define SESSIONS_STRM_CHUNK_SIZE 1024
# endif
#endif

typedef struct SessionHook SessionHook;
struct SessionHook {
  void *pCtx;
  int (*xOld)(void*,int,sqlite3_value**);
  int (*xNew)(void*,int,sqlite3_value**);
  int (*xCount)(void*);
  int (*xDepth)(void*);
};

/*
** Session handle structure.
*/
struct sqlite3_session {
  sqlite3 *db;                    /* Database handle session is attached to */
  char *zDb;                      /* Name of database session is attached to */
  int bEnable;                    /* True if currently recording */
  int bIndirect;                  /* True if all changes are indirect */
  int bAutoAttach;                /* True to auto-attach tables */
  int rc;                         /* Non-zero if an error has occurred */
  void *pFilterCtx;               /* First argument to pass to xTableFilter */
  int (*xTableFilter)(void *pCtx, const char *zTab);
  sqlite3_session *pNext;         /* Next session object on same db. */
  SessionTable *pTable;           /* List of attached tables */
  SessionHook hook;               /* APIs to grab new and old data with */
};

/*
** Instances of this structure are used to build strings or binary records.
*/
struct SessionBuffer {
  u8 *aBuf;                       /* Pointer to changeset buffer */
  int nBuf;                       /* Size of buffer aBuf */
  int nAlloc;                     /* Size of allocation containing aBuf */
};

/*
** An object of this type is used internally as an abstraction for 
** input data. Input data may be supplied either as a single large buffer
** (e.g. sqlite3changeset_start()) or using a stream function (e.g.
**  sqlite3changeset_start_strm()).
*/
struct SessionInput {
  int bNoDiscard;                 /* If true, discard no data */
  int iCurrent;                   /* Offset in aData[] of current change */
  int iNext;                      /* Offset in aData[] of next change */
  u8 *aData;                      /* Pointer to buffer containing changeset */
  int nData;                      /* Number of bytes in aData */

  SessionBuffer buf;              /* Current read buffer */
  int (*xInput)(void*, void*, int*);        /* Input stream call (or NULL) */
  void *pIn;                                /* First argument to xInput */
  int bEof;                       /* Set to true after xInput finished */
};

/*
** Structure for changeset iterators.
*/
struct sqlite3_changeset_iter {
  SessionInput in;                /* Input buffer or stream */
  SessionBuffer tblhdr;           /* Buffer to hold apValue/zTab/abPK/ */
  int bPatchset;                  /* True if this is a patchset */
  int rc;                         /* Iterator error code */
  sqlite3_stmt *pConflict;        /* Points to conflicting row, if any */
  char *zTab;                     /* Current table */
  int nCol;                       /* Number of columns in zTab */
  int op;                         /* Current operation */
  int bIndirect;                  /* True if current change was indirect */
  u8 *abPK;                       /* Primary key array */
  sqlite3_value **apValue;        /* old.* and new.* values */
};

/*
** Each session object maintains a set of the following structures, one
** for each table the session object is monitoring. The structures are
** stored in a linked list starting at sqlite3_session.pTable.
**
** The keys of the SessionTable.aChange[] hash table are all rows that have
** been modified in any way since the session object was attached to the
** table.
**
** The data associated with each hash-table entry is a structure containing
** a subset of the initial values that the modified row contained at the
** start of the session. Or no initial values if the row was inserted.
*/
struct SessionTable {
  SessionTable *pNext;
  char *zName;                    /* Local name of table */
  int nCol;                       /* Number of columns in table zName */
  const char **azCol;             /* Column names */
  u8 *abPK;                       /* Array of primary key flags */
  int nEntry;                     /* Total number of entries in hash table */
  int nChange;                    /* Size of apChange[] array */
  SessionChange **apChange;       /* Hash table buckets */
};

/* 
** RECORD FORMAT:
**
** The following record format is similar to (but not compatible with) that 
** used in SQLite database files. This format is used as part of the 
** change-set binary format, and so must be architecture independent.
**
** Unlike the SQLite database record format, each field is self-contained -
** there is no separation of header and data. Each field begins with a
** single byte describing its type, as follows:
**
**       0x00: Undefined value.
**       0x01: Integer value.
**       0x02: Real value.
**       0x03: Text value.
**       0x04: Blob value.
**       0x05: SQL NULL value.
**
** Note that the above match the definitions of SQLITE_INTEGER, SQLITE_TEXT
** and so on in sqlite3.h. For undefined and NULL values, the field consists
** only of the single type byte. For other types of values, the type byte
** is followed by:
**
**   Text values:
**     A varint containing the number of bytes in the value (encoded using
**     UTF-8). Followed by a buffer containing the UTF-8 representation
**     of the text value. There is no nul terminator.
**
**   Blob values:
**     A varint containing the number of bytes in the value, followed by
**     a buffer containing the value itself.
**
**   Integer values:
**     An 8-byte big-endian integer value.
**
**   Real values:
**     An 8-byte big-endian IEEE 754-2008 real value.
**
** Varint values are encoded in the same way as varints in the SQLite 
** record format.
**
** CHANGESET FORMAT:
**
** A changeset is a collection of DELETE, UPDATE and INSERT operations on
** one or more tables. Operations on a single table are grouped together,
** but may occur in any order (i.e. deletes, updates and inserts are all
** mixed together).
**
** Each group of changes begins with a table header:
**
**   1 byte: Constant 0x54 (capital 'T')
**   Varint: Number of columns in the table.
**   nCol bytes: 0x01 for PK columns, 0x00 otherwise.
**   N bytes: Unqualified table name (encoded using UTF-8). Nul-terminated.
**
** Followed by one or more changes to the table.
**
**   1 byte: Either SQLITE_INSERT (0x12), UPDATE (0x17) or DELETE (0x09).
**   1 byte: The "indirect-change" flag.
**   old.* record: (delete and update only)
**   new.* record: (insert and update only)
**
** The "old.*" and "new.*" records, if present, are N field records in the
** format described above under "RECORD FORMAT", where N is the number of
** columns in the table. The i'th field of each record is associated with
** the i'th column of the table, counting from left to right in the order
** in which columns were declared in the CREATE TABLE statement.
**
** The new.* record that is part of each INSERT change contains the values
** that make up the new row. Similarly, the old.* record that is part of each
** DELETE change contains the values that made up the row that was deleted 
** from the database. In the changeset format, the records that are part
** of INSERT or DELETE changes never contain any undefined (type byte 0x00)
** fields.
**
** Within the old.* record associated with an UPDATE change, all fields
** associated with table columns that are not PRIMARY KEY columns and are
** not modified by the UPDATE change are set to "undefined". Other fields
** are set to the values that made up the row before the UPDATE that the
** change records took place. Within the new.* record, fields associated 
** with table columns modified by the UPDATE change contain the new 
** values. Fields associated with table columns that are not modified
** are set to "undefined".
**
** PATCHSET FORMAT:
**
** A patchset is also a collection of changes. It is similar to a changeset,
** but leaves undefined those fields that are not useful if no conflict
** resolution is required when applying the changeset.
**
** Each group of changes begins with a table header:
**
**   1 byte: Constant 0x50 (capital 'P')
**   Varint: Number of columns in the table.
**   nCol bytes: 0x01 for PK columns, 0x00 otherwise.
**   N bytes: Unqualified table name (encoded using UTF-8). Nul-terminated.
**
** Followed by one or more changes to the table.
**
**   1 byte: Either SQLITE_INSERT (0x12), UPDATE (0x17) or DELETE (0x09).
**   1 byte: The "indirect-change" flag.
**   single record: (PK fields for DELETE, PK and modified fields for UPDATE,
**                   full record for INSERT).
**
** As in the changeset format, each field of the single record that is part
** of a patchset change is associated with the correspondingly positioned
** table column, counting from left to right within the CREATE TABLE 
** statement.
**
** For a DELETE change, all fields within the record except those associated
** with PRIMARY KEY columns are set to "undefined". The PRIMARY KEY fields
** contain the values identifying the row to delete.
**
** For an UPDATE change, all fields except those associated with PRIMARY KEY
** columns and columns that are modified by the UPDATE are set to "undefined".
** PRIMARY KEY fields contain the values identifying the table row to update,
** and fields associated with modified columns contain the new column values.
**
** The records associated with INSERT changes are in the same format as for
** changesets. It is not possible for a record associated with an INSERT
** change to contain a field set to "undefined".
*/

/*
** For each row modified during a session, there exists a single instance of
** this structure stored in a SessionTable.aChange[] hash table.
*/
struct SessionChange {
  int op;                         /* One of UPDATE, DELETE, INSERT */
  int bIndirect;                  /* True if this change is "indirect" */
  int nRecord;                    /* Number of bytes in buffer aRecord[] */
  u8 *aRecord;                    /* Buffer containing old.* record */
  SessionChange *pNext;           /* For hash-table collisions */
};

/*
** Write a varint with value iVal into the buffer at aBuf. Return the 
** number of bytes written.
*/
static int sessionVarintPut(u8 *aBuf, int iVal){
  return putVarint32(aBuf, iVal);
}

/*
** Return the number of bytes required to store value iVal as a varint.
*/
static int sessionVarintLen(int iVal){
  return sqlite3VarintLen(iVal);
}

/*
** Read a varint value from aBuf[] into *piVal. Return the number of 
** bytes read.
*/
static int sessionVarintGet(u8 *aBuf, int *piVal){
  return getVarint32(aBuf, *piVal);
}

/*
** Read a 64-bit big-endian integer value from buffer aRec[]. Return
** the value read.
*/
static sqlite3_int64 sessionGetI64(u8 *aRec){
  return (((sqlite3_int64)aRec[0]) << 56)
       + (((sqlite3_int64)aRec[1]) << 48)
       + (((sqlite3_int64)aRec[2]) << 40)
       + (((sqlite3_int64)aRec[3]) << 32)
       + (((sqlite3_int64)aRec[4]) << 24)
       + (((sqlite3_int64)aRec[5]) << 16)
       + (((sqlite3_int64)aRec[6]) <<  8)
       + (((sqlite3_int64)aRec[7]) <<  0);
}

/*
** Write a 64-bit big-endian integer value to the buffer aBuf[].
*/
static void sessionPutI64(u8 *aBuf, sqlite3_int64 i){
  aBuf[0] = (i>>56) & 0xFF;
  aBuf[1] = (i>>48) & 0xFF;
  aBuf[2] = (i>>40) & 0xFF;
  aBuf[3] = (i>>32) & 0xFF;
  aBuf[4] = (i>>24) & 0xFF;
  aBuf[5] = (i>>16) & 0xFF;
  aBuf[6] = (i>> 8) & 0xFF;
  aBuf[7] = (i>> 0) & 0xFF;
}

/*
** This function is used to serialize the contents of value pValue (see
** comment titled "RECORD FORMAT" above).
**
** If it is non-NULL, the serialized form of the value is written to 
** buffer aBuf. *pnWrite is set to the number of bytes written before
** returning. Or, if aBuf is NULL, the only thing this function does is
** set *pnWrite.
**
** If no error occurs, SQLITE_OK is returned. Or, if an OOM error occurs
** within a call to sqlite3_value_text() (may fail if the db is utf-16)) 
** SQLITE_NOMEM is returned.
*/
static int sessionSerializeValue(
  u8 *aBuf,                       /* If non-NULL, write serialized value here */
  sqlite3_value *pValue,          /* Value to serialize */
  int *pnWrite                    /* IN/OUT: Increment by bytes written */
){
  int nByte;                      /* Size of serialized value in bytes */

  if( pValue ){
    int eType;                    /* Value type (SQLITE_NULL, TEXT etc.) */
  
    eType = sqlite3_value_type(pValue);
    if( aBuf ) aBuf[0] = eType;
  
    switch( eType ){
      case SQLITE_NULL: 
        nByte = 1;
        break;
  
      case SQLITE_INTEGER: 
      case SQLITE_FLOAT:
        if( aBuf ){
          /* TODO: SQLite does something special to deal with mixed-endian
          ** floating point values (e.g. ARM7). This code probably should
          ** too.  */
          u64 i;
          if( eType==SQLITE_INTEGER ){
            i = (u64)sqlite3_value_int64(pValue);
          }else{
            double r;
            assert( sizeof(double)==8 && sizeof(u64)==8 );
            r = sqlite3_value_double(pValue);
            memcpy(&i, &r, 8);
          }
          sessionPutI64(&aBuf[1], i);
        }
        nByte = 9; 
        break;
  
      default: {
        u8 *z;
        int n;
        int nVarint;
  
        assert( eType==SQLITE_TEXT || eType==SQLITE_BLOB );
        if( eType==SQLITE_TEXT ){
          z = (u8 *)sqlite3_value_text(pValue);
        }else{
          z = (u8 *)sqlite3_value_blob(pValue);
        }
        n = sqlite3_value_bytes(pValue);
        if( z==0 && (eType!=SQLITE_BLOB || n>0) ) return SQLITE_NOMEM;
        nVarint = sessionVarintLen(n);
  
        if( aBuf ){
          sessionVarintPut(&aBuf[1], n);
          memcpy(&aBuf[nVarint + 1], eType==SQLITE_TEXT ? 
              sqlite3_value_text(pValue) : sqlite3_value_blob(pValue), n
          );
        }
  
        nByte = 1 + nVarint + n;
        break;
      }
    }
  }else{
    nByte = 1;
    if( aBuf ) aBuf[0] = '\0';
  }

  if( pnWrite ) *pnWrite += nByte;
  return SQLITE_OK;
}


/*
** This macro is used to calculate hash key values for data structures. In
** order to use this macro, the entire data structure must be represented
** as a series of unsigned integers. In order to calculate a hash-key value
** for a data structure represented as three such integers, the macro may
** then be used as follows:
**
**    int hash_key_value;
**    hash_key_value = HASH_APPEND(0, <value 1>);
**    hash_key_value = HASH_APPEND(hash_key_value, <value 2>);
**    hash_key_value = HASH_APPEND(hash_key_value, <value 3>);
**
** In practice, the data structures this macro is used for are the primary
** key values of modified rows.
*/
#define HASH_APPEND(hash, add) ((hash) << 3) ^ (hash) ^ (unsigned int)(add)

/*
** Append the hash of the 64-bit integer passed as the second argument to the
** hash-key value passed as the first. Return the new hash-key value.
*/
static unsigned int sessionHashAppendI64(unsigned int h, i64 i){
  h = HASH_APPEND(h, i & 0xFFFFFFFF);
  return HASH_APPEND(h, (i>>32)&0xFFFFFFFF);
}

/*
** Append the hash of the blob passed via the second and third arguments to 
** the hash-key value passed as the first. Return the new hash-key value.
*/
static unsigned int sessionHashAppendBlob(unsigned int h, int n, const u8 *z){
  int i;
  for(i=0; i<n; i++) h = HASH_APPEND(h, z[i]);
  return h;
}

/*
** Append the hash of the data type passed as the second argument to the
** hash-key value passed as the first. Return the new hash-key value.
*/
static unsigned int sessionHashAppendType(unsigned int h, int eType){
  return HASH_APPEND(h, eType);
}

/*
** This function may only be called from within a pre-update callback.
** It calculates a hash based on the primary key values of the old.* or 
** new.* row currently available and, assuming no error occurs, writes it to
** *piHash before returning. If the primary key contains one or more NULL
** values, *pbNullPK is set to true before returning.
**
** If an error occurs, an SQLite error code is returned and the final values
** of *piHash asn *pbNullPK are undefined. Otherwise, SQLITE_OK is returned
** and the output variables are set as described above.
*/
static int sessionPreupdateHash(
  sqlite3_session *pSession,      /* Session object that owns pTab */
  SessionTable *pTab,             /* Session table handle */
  int bNew,                       /* True to hash the new.* PK */
  int *piHash,                    /* OUT: Hash value */
  int *pbNullPK                   /* OUT: True if there are NULL values in PK */
){
  unsigned int h = 0;             /* Hash value to return */
  int i;                          /* Used to iterate through columns */

  assert( *pbNullPK==0 );
  assert( pTab->nCol==pSession->hook.xCount(pSession->hook.pCtx) );
  for(i=0; i<pTab->nCol; i++){
    if( pTab->abPK[i] ){
      int rc;
      int eType;
      sqlite3_value *pVal;

      if( bNew ){
        rc = pSession->hook.xNew(pSession->hook.pCtx, i, &pVal);
      }else{
        rc = pSession->hook.xOld(pSession->hook.pCtx, i, &pVal);
      }
      if( rc!=SQLITE_OK ) return rc;

      eType = sqlite3_value_type(pVal);
      h = sessionHashAppendType(h, eType);
      if( eType==SQLITE_INTEGER || eType==SQLITE_FLOAT ){
        i64 iVal;
        if( eType==SQLITE_INTEGER ){
          iVal = sqlite3_value_int64(pVal);
        }else{
          double rVal = sqlite3_value_double(pVal);
          assert( sizeof(iVal)==8 && sizeof(rVal)==8 );
          memcpy(&iVal, &rVal, 8);
        }
        h = sessionHashAppendI64(h, iVal);
      }else if( eType==SQLITE_TEXT || eType==SQLITE_BLOB ){
        const u8 *z;
        int n;
        if( eType==SQLITE_TEXT ){
          z = (const u8 *)sqlite3_value_text(pVal);
        }else{
          z = (const u8 *)sqlite3_value_blob(pVal);
        }
        n = sqlite3_value_bytes(pVal);
        if( !z && (eType!=SQLITE_BLOB || n>0) ) return SQLITE_NOMEM;
        h = sessionHashAppendBlob(h, n, z);
      }else{
        assert( eType==SQLITE_NULL );
        *pbNullPK = 1;
      }
    }
  }

  *piHash = (h % pTab->nChange);
  return SQLITE_OK;
}

/*
** The buffer that the argument points to contains a serialized SQL value.
** Return the number of bytes of space occupied by the value (including
** the type byte).
*/
static int sessionSerialLen(u8 *a){
  int e = *a;
  int n;
  if( e==0 ) return 1;
  if( e==SQLITE_NULL ) return 1;
  if( e==SQLITE_INTEGER || e==SQLITE_FLOAT ) return 9;
  return sessionVarintGet(&a[1], &n) + 1 + n;
}

/*
** Based on the primary key values stored in change aRecord, calculate a
** hash key. Assume the has table has nBucket buckets. The hash keys
** calculated by this function are compatible with those calculated by
** sessionPreupdateHash().
**
** The bPkOnly argument is non-zero if the record at aRecord[] is from
** a patchset DELETE. In this case the non-PK fields are omitted entirely.
*/
static unsigned int sessionChangeHash(
  SessionTable *pTab,             /* Table handle */
  int bPkOnly,                    /* Record consists of PK fields only */
  u8 *aRecord,                    /* Change record */
  int nBucket                     /* Assume this many buckets in hash table */
){
  unsigned int h = 0;             /* Value to return */
  int i;                          /* Used to iterate through columns */
  u8 *a = aRecord;                /* Used to iterate through change record */

  for(i=0; i<pTab->nCol; i++){
    int eType = *a;
    int isPK = pTab->abPK[i];
    if( bPkOnly && isPK==0 ) continue;

    /* It is not possible for eType to be SQLITE_NULL here. The session 
    ** module does not record changes for rows with NULL values stored in
    ** primary key columns. */
    assert( eType==SQLITE_INTEGER || eType==SQLITE_FLOAT 
         || eType==SQLITE_TEXT || eType==SQLITE_BLOB 
         || eType==SQLITE_NULL || eType==0 
    );
    assert( !isPK || (eType!=0 && eType!=SQLITE_NULL) );

    if( isPK ){
      a++;
      h = sessionHashAppendType(h, eType);
      if( eType==SQLITE_INTEGER || eType==SQLITE_FLOAT ){
        h = sessionHashAppendI64(h, sessionGetI64(a));
        a += 8;
      }else{
        int n; 
        a += sessionVarintGet(a, &n);
        h = sessionHashAppendBlob(h, n, a);
        a += n;
      }
    }else{
      a += sessionSerialLen(a);
    }
  }
  return (h % nBucket);
}

/*
** Arguments aLeft and aRight are pointers to change records for table pTab.
** This function returns true if the two records apply to the same row (i.e.
** have the same values stored in the primary key columns), or false 
** otherwise.
*/
static int sessionChangeEqual(
  SessionTable *pTab,             /* Table used for PK definition */
  int bLeftPkOnly,                /* True if aLeft[] contains PK fields only */
  u8 *aLeft,                      /* Change record */
  int bRightPkOnly,               /* True if aRight[] contains PK fields only */
  u8 *aRight                      /* Change record */
){
  u8 *a1 = aLeft;                 /* Cursor to iterate through aLeft */
  u8 *a2 = aRight;                /* Cursor to iterate through aRight */
  int iCol;                       /* Used to iterate through table columns */

  for(iCol=0; iCol<pTab->nCol; iCol++){
    int n1 = sessionSerialLen(a1);
    int n2 = sessionSerialLen(a2);

    if( pTab->abPK[iCol] && (n1!=n2 || memcmp(a1, a2, n1)) ){
      return 0;
    }
    if( pTab->abPK[iCol] || bLeftPkOnly==0 ) a1 += n1;
    if( pTab->abPK[iCol] || bRightPkOnly==0 ) a2 += n2;
  }

  return 1;
}

/*
** Arguments aLeft and aRight both point to buffers containing change
** records with nCol columns. This function "merges" the two records into
** a single records which is written to the buffer at *paOut. *paOut is
** then set to point to one byte after the last byte written before 
** returning.
**
** The merging of records is done as follows: For each column, if the 
** aRight record contains a value for the column, copy the value from
** their. Otherwise, if aLeft contains a value, copy it. If neither
** record contains a value for a given column, then neither does the
** output record.
*/
static void sessionMergeRecord(
  u8 **paOut, 
  int nCol,
  u8 *aLeft,
  u8 *aRight
){
  u8 *a1 = aLeft;                 /* Cursor used to iterate through aLeft */
  u8 *a2 = aRight;                /* Cursor used to iterate through aRight */
  u8 *aOut = *paOut;              /* Output cursor */
  int iCol;                       /* Used to iterate from 0 to nCol */

  for(iCol=0; iCol<nCol; iCol++){
    int n1 = sessionSerialLen(a1);
    int n2 = sessionSerialLen(a2);
    if( *a2 ){
      memcpy(aOut, a2, n2);
      aOut += n2;
    }else{
      memcpy(aOut, a1, n1);
      aOut += n1;
    }
    a1 += n1;
    a2 += n2;
  }

  *paOut = aOut;
}

/*
** This is a helper function used by sessionMergeUpdate().
**
** When this function is called, both *paOne and *paTwo point to a value 
** within a change record. Before it returns, both have been advanced so 
** as to point to the next value in the record.
**
** If, when this function is called, *paTwo points to a valid value (i.e.
** *paTwo[0] is not 0x00 - the "no value" placeholder), a copy of the *paTwo
** pointer is returned and *pnVal is set to the number of bytes in the 
** serialized value. Otherwise, a copy of *paOne is returned and *pnVal
** set to the number of bytes in the value at *paOne. If *paOne points
** to the "no value" placeholder, *pnVal is set to 1. In other words:
**
**   if( *paTwo is valid ) return *paTwo;
**   return *paOne;
**
*/
static u8 *sessionMergeValue(
  u8 **paOne,                     /* IN/OUT: Left-hand buffer pointer */
  u8 **paTwo,                     /* IN/OUT: Right-hand buffer pointer */
  int *pnVal                      /* OUT: Bytes in returned value */
){
  u8 *a1 = *paOne;
  u8 *a2 = *paTwo;
  u8 *pRet = 0;
  int n1;

  assert( a1 );
  if( a2 ){
    int n2 = sessionSerialLen(a2);
    if( *a2 ){
      *pnVal = n2;
      pRet = a2;
    }
    *paTwo = &a2[n2];
  }

  n1 = sessionSerialLen(a1);
  if( pRet==0 ){
    *pnVal = n1;
    pRet = a1;
  }
  *paOne = &a1[n1];

  return pRet;
}

/*
** This function is used by changeset_concat() to merge two UPDATE changes
** on the same row.
*/
static int sessionMergeUpdate(
  u8 **paOut,                     /* IN/OUT: Pointer to output buffer */
  SessionTable *pTab,             /* Table change pertains to */
  int bPatchset,                  /* True if records are patchset records */
  u8 *aOldRecord1,                /* old.* record for first change */
  u8 *aOldRecord2,                /* old.* record for second change */
  u8 *aNewRecord1,                /* new.* record for first change */
  u8 *aNewRecord2                 /* new.* record for second change */
){
  u8 *aOld1 = aOldRecord1;
  u8 *aOld2 = aOldRecord2;
  u8 *aNew1 = aNewRecord1;
  u8 *aNew2 = aNewRecord2;

  u8 *aOut = *paOut;
  int i;

  if( bPatchset==0 ){
    int bRequired = 0;

    assert( aOldRecord1 && aNewRecord1 );

    /* Write the old.* vector first. */
    for(i=0; i<pTab->nCol; i++){
      int nOld;
      u8 *aOld;
      int nNew;
      u8 *aNew;

      aOld = sessionMergeValue(&aOld1, &aOld2, &nOld);
      aNew = sessionMergeValue(&aNew1, &aNew2, &nNew);
      if( pTab->abPK[i] || nOld!=nNew || memcmp(aOld, aNew, nNew) ){
        if( pTab->abPK[i]==0 ) bRequired = 1;
        memcpy(aOut, aOld, nOld);
        aOut += nOld;
      }else{
        *(aOut++) = '\0';
      }
    }

    if( !bRequired ) return 0;
  }

  /* Write the new.* vector */
  aOld1 = aOldRecord1;
  aOld2 = aOldRecord2;
  aNew1 = aNewRecord1;
  aNew2 = aNewRecord2;
  for(i=0; i<pTab->nCol; i++){
    int nOld;
    u8 *aOld;
    int nNew;
    u8 *aNew;

    aOld = sessionMergeValue(&aOld1, &aOld2, &nOld);
    aNew = sessionMergeValue(&aNew1, &aNew2, &nNew);
    if( bPatchset==0 
     && (pTab->abPK[i] || (nOld==nNew && 0==memcmp(aOld, aNew, nNew))) 
    ){
      *(aOut++) = '\0';
    }else{
      memcpy(aOut, aNew, nNew);
      aOut += nNew;
    }
  }

  *paOut = aOut;
  return 1;
}

/*
** This function is only called from within a pre-update-hook callback.
** It determines if the current pre-update-hook change affects the same row
** as the change stored in argument pChange. If so, it returns true. Otherwise
** if the pre-update-hook does not affect the same row as pChange, it returns
** false.
*/
static int sessionPreupdateEqual(
  sqlite3_session *pSession,      /* Session object that owns SessionTable */
  SessionTable *pTab,             /* Table associated with change */
  SessionChange *pChange,         /* Change to compare to */
  int op                          /* Current pre-update operation */
){
  int iCol;                       /* Used to iterate through columns */
  u8 *a = pChange->aRecord;       /* Cursor used to scan change record */

  assert( op==SQLITE_INSERT || op==SQLITE_UPDATE || op==SQLITE_DELETE );
  for(iCol=0; iCol<pTab->nCol; iCol++){
    if( !pTab->abPK[iCol] ){
      a += sessionSerialLen(a);
    }else{
      sqlite3_value *pVal;        /* Value returned by preupdate_new/old */
      int rc;                     /* Error code from preupdate_new/old */
      int eType = *a++;           /* Type of value from change record */

      /* The following calls to preupdate_new() and preupdate_old() can not
      ** fail. This is because they cache their return values, and by the
      ** time control flows to here they have already been called once from
      ** within sessionPreupdateHash(). The first two asserts below verify
      ** this (that the method has already been called). */
      if( op==SQLITE_INSERT ){
        /* assert( db->pPreUpdate->pNewUnpacked || db->pPreUpdate->aNew ); */
        rc = pSession->hook.xNew(pSession->hook.pCtx, iCol, &pVal);
      }else{
        /* assert( db->pPreUpdate->pUnpacked ); */
        rc = pSession->hook.xOld(pSession->hook.pCtx, iCol, &pVal);
      }
      assert( rc==SQLITE_OK );
      if( sqlite3_value_type(pVal)!=eType ) return 0;

      /* A SessionChange object never has a NULL value in a PK column */
      assert( eType==SQLITE_INTEGER || eType==SQLITE_FLOAT
           || eType==SQLITE_BLOB    || eType==SQLITE_TEXT
      );

      if( eType==SQLITE_INTEGER || eType==SQLITE_FLOAT ){
        i64 iVal = sessionGetI64(a);
        a += 8;
        if( eType==SQLITE_INTEGER ){
          if( sqlite3_value_int64(pVal)!=iVal ) return 0;
        }else{
          double rVal;
          assert( sizeof(iVal)==8 && sizeof(rVal)==8 );
          memcpy(&rVal, &iVal, 8);
          if( sqlite3_value_double(pVal)!=rVal ) return 0;
        }
      }else{
        int n;
        const u8 *z;
        a += sessionVarintGet(a, &n);
        if( sqlite3_value_bytes(pVal)!=n ) return 0;
        if( eType==SQLITE_TEXT ){
          z = sqlite3_value_text(pVal);
        }else{
          z = sqlite3_value_blob(pVal);
        }
        if( memcmp(a, z, n) ) return 0;
        a += n;
        break;
      }
    }
  }

  return 1;
}

/*
** If required, grow the hash table used to store changes on table pTab 
** (part of the session pSession). If a fatal OOM error occurs, set the
** session object to failed and return SQLITE_ERROR. Otherwise, return
** SQLITE_OK.
**
** It is possible that a non-fatal OOM error occurs in this function. In
** that case the hash-table does not grow, but SQLITE_OK is returned anyway.
** Growing the hash table in this case is a performance optimization only,
** it is not required for correct operation.
*/
static int sessionGrowHash(int bPatchset, SessionTable *pTab){
  if( pTab->nChange==0 || pTab->nEntry>=(pTab->nChange/2) ){
    int i;
    SessionChange **apNew;
    int nNew = (pTab->nChange ? pTab->nChange : 128) * 2;

    apNew = (SessionChange **)sqlite3_malloc(sizeof(SessionChange *) * nNew);
    if( apNew==0 ){
      if( pTab->nChange==0 ){
        return SQLITE_ERROR;
      }
      return SQLITE_OK;
    }
    memset(apNew, 0, sizeof(SessionChange *) * nNew);

    for(i=0; i<pTab->nChange; i++){
      SessionChange *p;
      SessionChange *pNext;
      for(p=pTab->apChange[i]; p; p=pNext){
        int bPkOnly = (p->op==SQLITE_DELETE && bPatchset);
        int iHash = sessionChangeHash(pTab, bPkOnly, p->aRecord, nNew);
        pNext = p->pNext;
        p->pNext = apNew[iHash];
        apNew[iHash] = p;
      }
    }

    sqlite3_free(pTab->apChange);
    pTab->nChange = nNew;
    pTab->apChange = apNew;
  }

  return SQLITE_OK;
}

/*
** This function queries the database for the names of the columns of table
** zThis, in schema zDb. It is expected that the table has nCol columns. If
** not, SQLITE_SCHEMA is returned and none of the output variables are
** populated.
**
** Otherwise, if they are not NULL, variable *pnCol is set to the number
** of columns in the database table and variable *pzTab is set to point to a
** nul-terminated copy of the table name. *pazCol (if not NULL) is set to
** point to an array of pointers to column names. And *pabPK (again, if not
** NULL) is set to point to an array of booleans - true if the corresponding
** column is part of the primary key.
**
** For example, if the table is declared as:
**
**     CREATE TABLE tbl1(w, x, y, z, PRIMARY KEY(w, z));
**
** Then the four output variables are populated as follows:
**
**     *pnCol  = 4
**     *pzTab  = "tbl1"
**     *pazCol = {"w", "x", "y", "z"}
**     *pabPK  = {1, 0, 0, 1}
**
** All returned buffers are part of the same single allocation, which must
** be freed using sqlite3_free() by the caller. If pazCol was not NULL, then
** pointer *pazCol should be freed to release all memory. Otherwise, pointer
** *pabPK. It is illegal for both pazCol and pabPK to be NULL.
*/
static int sessionTableInfo(
  sqlite3 *db,                    /* Database connection */
  const char *zDb,                /* Name of attached database (e.g. "main") */
  const char *zThis,              /* Table name */
  int *pnCol,                     /* OUT: number of columns */
  const char **pzTab,             /* OUT: Copy of zThis */
  const char ***pazCol,           /* OUT: Array of column names for table */
  u8 **pabPK                      /* OUT: Array of booleans - true for PK col */
){
  char *zPragma;
  sqlite3_stmt *pStmt;
  int rc;
  int nByte;
  int nDbCol = 0;
  int nThis;
  int i;
  u8 *pAlloc;
  char **azCol = 0;
  u8 *abPK;

  assert( pazCol && pabPK );

  nThis = sqlite3Strlen30(zThis);
  zPragma = sqlite3_mprintf("PRAGMA '%q'.table_info('%q')", zDb, zThis);
  if( !zPragma ) return SQLITE_NOMEM;

  rc = sqlite3_prepare_v2(db, zPragma, -1, &pStmt, 0);
  sqlite3_free(zPragma);
  if( rc!=SQLITE_OK ) return rc;

  nByte = nThis + 1;
  while( SQLITE_ROW==sqlite3_step(pStmt) ){
    nByte += sqlite3_column_bytes(pStmt, 1);
    nDbCol++;
  }
  rc = sqlite3_reset(pStmt);

  if( rc==SQLITE_OK ){
    nByte += nDbCol * (sizeof(const char *) + sizeof(u8) + 1);
    pAlloc = sqlite3_malloc(nByte);
    if( pAlloc==0 ){
      rc = SQLITE_NOMEM;
    }
  }
  if( rc==SQLITE_OK ){
    azCol = (char **)pAlloc;
    pAlloc = (u8 *)&azCol[nDbCol];
    abPK = (u8 *)pAlloc;
    pAlloc = &abPK[nDbCol];
    if( pzTab ){
      memcpy(pAlloc, zThis, nThis+1);
      *pzTab = (char *)pAlloc;
      pAlloc += nThis+1;
    }
  
    i = 0;
    while( SQLITE_ROW==sqlite3_step(pStmt) ){
      int nName = sqlite3_column_bytes(pStmt, 1);
      const unsigned char *zName = sqlite3_column_text(pStmt, 1);
      if( zName==0 ) break;
      memcpy(pAlloc, zName, nName+1);
      azCol[i] = (char *)pAlloc;
      pAlloc += nName+1;
      abPK[i] = sqlite3_column_int(pStmt, 5);
      i++;
    }
    rc = sqlite3_reset(pStmt);
  
  }

  /* If successful, populate the output variables. Otherwise, zero them and
  ** free any allocation made. An error code will be returned in this case.
  */
  if( rc==SQLITE_OK ){
    *pazCol = (const char **)azCol;
    *pabPK = abPK;
    *pnCol = nDbCol;
  }else{
    *pazCol = 0;
    *pabPK = 0;
    *pnCol = 0;
    if( pzTab ) *pzTab = 0;
    sqlite3_free(azCol);
  }
  sqlite3_finalize(pStmt);
  return rc;
}

/*
** This function is only called from within a pre-update handler for a
** write to table pTab, part of session pSession. If this is the first
** write to this table, initalize the SessionTable.nCol, azCol[] and
** abPK[] arrays accordingly.
**
** If an error occurs, an error code is stored in sqlite3_session.rc and
** non-zero returned. Or, if no error occurs but the table has no primary
** key, sqlite3_session.rc is left set to SQLITE_OK and non-zero returned to
** indicate that updates on this table should be ignored. SessionTable.abPK 
** is set to NULL in this case.
*/
static int sessionInitTable(sqlite3_session *pSession, SessionTable *pTab){
  if( pTab->nCol==0 ){
    u8 *abPK;
    assert( pTab->azCol==0 || pTab->abPK==0 );
    pSession->rc = sessionTableInfo(pSession->db, pSession->zDb, 
        pTab->zName, &pTab->nCol, 0, &pTab->azCol, &abPK
    );
    if( pSession->rc==SQLITE_OK ){
      int i;
      for(i=0; i<pTab->nCol; i++){
        if( abPK[i] ){
          pTab->abPK = abPK;
          break;
        }
      }
    }
  }
  return (pSession->rc || pTab->abPK==0);
}

/*
** This function is only called from with a pre-update-hook reporting a 
** change on table pTab (attached to session pSession). The type of change
** (UPDATE, INSERT, DELETE) is specified by the first argument.
**
** Unless one is already present or an error occurs, an entry is added
** to the changed-rows hash table associated with table pTab.
*/
static void sessionPreupdateOneChange(
  int op,                         /* One of SQLITE_UPDATE, INSERT, DELETE */
  sqlite3_session *pSession,      /* Session object pTab is attached to */
  SessionTable *pTab              /* Table that change applies to */
){
  int iHash; 
  int bNull = 0; 
  int rc = SQLITE_OK;

  if( pSession->rc ) return;

  /* Load table details if required */
  if( sessionInitTable(pSession, pTab) ) return;

  /* Check the number of columns in this xPreUpdate call matches the 
  ** number of columns in the table.  */
  if( pTab->nCol!=pSession->hook.xCount(pSession->hook.pCtx) ){
    pSession->rc = SQLITE_SCHEMA;
    return;
  }

  /* Grow the hash table if required */
  if( sessionGrowHash(0, pTab) ){
    pSession->rc = SQLITE_NOMEM;
    return;
  }

  /* Calculate the hash-key for this change. If the primary key of the row
  ** includes a NULL value, exit early. Such changes are ignored by the
  ** session module. */
  rc = sessionPreupdateHash(pSession, pTab, op==SQLITE_INSERT, &iHash, &bNull);
  if( rc!=SQLITE_OK ) goto error_out;

  if( bNull==0 ){
    /* Search the hash table for an existing record for this row. */
    SessionChange *pC;
    for(pC=pTab->apChange[iHash]; pC; pC=pC->pNext){
      if( sessionPreupdateEqual(pSession, pTab, pC, op) ) break;
    }

    if( pC==0 ){
      /* Create a new change object containing all the old values (if
      ** this is an SQLITE_UPDATE or SQLITE_DELETE), or just the PK
      ** values (if this is an INSERT). */
      SessionChange *pChange; /* New change object */
      int nByte;              /* Number of bytes to allocate */
      int i;                  /* Used to iterate through columns */
  
      assert( rc==SQLITE_OK );
      pTab->nEntry++;
  
      /* Figure out how large an allocation is required */
      nByte = sizeof(SessionChange);
      for(i=0; i<pTab->nCol; i++){
        sqlite3_value *p = 0;
        if( op!=SQLITE_INSERT ){
          TESTONLY(int trc = ) pSession->hook.xOld(pSession->hook.pCtx, i, &p);
          assert( trc==SQLITE_OK );
        }else if( pTab->abPK[i] ){
          TESTONLY(int trc = ) pSession->hook.xNew(pSession->hook.pCtx, i, &p);
          assert( trc==SQLITE_OK );
        }

        /* This may fail if SQLite value p contains a utf-16 string that must
        ** be converted to utf-8 and an OOM error occurs while doing so. */
        rc = sessionSerializeValue(0, p, &nByte);
        if( rc!=SQLITE_OK ) goto error_out;
      }
  
      /* Allocate the change object */
      pChange = (SessionChange *)sqlite3_malloc(nByte);
      if( !pChange ){
        rc = SQLITE_NOMEM;
        goto error_out;
      }else{
        memset(pChange, 0, sizeof(SessionChange));
        pChange->aRecord = (u8 *)&pChange[1];
      }
  
      /* Populate the change object. None of the preupdate_old(),
      ** preupdate_new() or SerializeValue() calls below may fail as all
      ** required values and encodings have already been cached in memory.
      ** It is not possible for an OOM to occur in this block. */
      nByte = 0;
      for(i=0; i<pTab->nCol; i++){
        sqlite3_value *p = 0;
        if( op!=SQLITE_INSERT ){
          pSession->hook.xOld(pSession->hook.pCtx, i, &p);
        }else if( pTab->abPK[i] ){
          pSession->hook.xNew(pSession->hook.pCtx, i, &p);
        }
        sessionSerializeValue(&pChange->aRecord[nByte], p, &nByte);
      }

      /* Add the change to the hash-table */
      if( pSession->bIndirect || pSession->hook.xDepth(pSession->hook.pCtx) ){
        pChange->bIndirect = 1;
      }
      pChange->nRecord = nByte;
      pChange->op = op;
      pChange->pNext = pTab->apChange[iHash];
      pTab->apChange[iHash] = pChange;

    }else if( pC->bIndirect ){
      /* If the existing change is considered "indirect", but this current
      ** change is "direct", mark the change object as direct. */
      if( pSession->hook.xDepth(pSession->hook.pCtx)==0 
       && pSession->bIndirect==0 
      ){
        pC->bIndirect = 0;
      }
    }
  }

  /* If an error has occurred, mark the session object as failed. */
 error_out:
  if( rc!=SQLITE_OK ){
    pSession->rc = rc;
  }
}

static int sessionFindTable(
  sqlite3_session *pSession, 
  const char *zName,
  SessionTable **ppTab
){
  int rc = SQLITE_OK;
  int nName = sqlite3Strlen30(zName);
  SessionTable *pRet;

  /* Search for an existing table */
  for(pRet=pSession->pTable; pRet; pRet=pRet->pNext){
    if( 0==sqlite3_strnicmp(pRet->zName, zName, nName+1) ) break;
  }

  if( pRet==0 && pSession->bAutoAttach ){
    /* If there is a table-filter configured, invoke it. If it returns 0,
    ** do not automatically add the new table. */
    if( pSession->xTableFilter==0
     || pSession->xTableFilter(pSession->pFilterCtx, zName) 
    ){
      rc = sqlite3session_attach(pSession, zName);
      if( rc==SQLITE_OK ){
        for(pRet=pSession->pTable; pRet->pNext; pRet=pRet->pNext);
        assert( 0==sqlite3_strnicmp(pRet->zName, zName, nName+1) );
      }
    }
  }

  assert( rc==SQLITE_OK || pRet==0 );
  *ppTab = pRet;
  return rc;
}

/*
** The 'pre-update' hook registered by this module with SQLite databases.
*/
static void xPreUpdate(
  void *pCtx,                     /* Copy of third arg to preupdate_hook() */
  sqlite3 *db,                    /* Database handle */
  int op,                         /* SQLITE_UPDATE, DELETE or INSERT */
  char const *zDb,                /* Database name */
  char const *zName,              /* Table name */
  sqlite3_int64 iKey1,            /* Rowid of row about to be deleted/updated */
  sqlite3_int64 iKey2             /* New rowid value (for a rowid UPDATE) */
){
  sqlite3_session *pSession;
  int nDb = sqlite3Strlen30(zDb);

  assert( sqlite3_mutex_held(db->mutex) );

  for(pSession=(sqlite3_session *)pCtx; pSession; pSession=pSession->pNext){
    SessionTable *pTab;

    /* If this session is attached to a different database ("main", "temp" 
    ** etc.), or if it is not currently enabled, there is nothing to do. Skip 
    ** to the next session object attached to this database. */
    if( pSession->bEnable==0 ) continue;
    if( pSession->rc ) continue;
    if( sqlite3_strnicmp(zDb, pSession->zDb, nDb+1) ) continue;

    pSession->rc = sessionFindTable(pSession, zName, &pTab);
    if( pTab ){
      assert( pSession->rc==SQLITE_OK );
      sessionPreupdateOneChange(op, pSession, pTab);
      if( op==SQLITE_UPDATE ){
        sessionPreupdateOneChange(SQLITE_INSERT, pSession, pTab);
      }
    }
  }
}

/*
** The pre-update hook implementations.
*/
static int sessionPreupdateOld(void *pCtx, int iVal, sqlite3_value **ppVal){
  return sqlite3_preupdate_old((sqlite3*)pCtx, iVal, ppVal);
}
static int sessionPreupdateNew(void *pCtx, int iVal, sqlite3_value **ppVal){
  return sqlite3_preupdate_new((sqlite3*)pCtx, iVal, ppVal);
}
static int sessionPreupdateCount(void *pCtx){
  return sqlite3_preupdate_count((sqlite3*)pCtx);
}
static int sessionPreupdateDepth(void *pCtx){
  return sqlite3_preupdate_depth((sqlite3*)pCtx);
}

/*
** Install the pre-update hooks on the session object passed as the only
** argument.
*/
static void sessionPreupdateHooks(
  sqlite3_session *pSession
){
  pSession->hook.pCtx = (void*)pSession->db;
  pSession->hook.xOld = sessionPreupdateOld;
  pSession->hook.xNew = sessionPreupdateNew;
  pSession->hook.xCount = sessionPreupdateCount;
  pSession->hook.xDepth = sessionPreupdateDepth;
}

typedef struct SessionDiffCtx SessionDiffCtx;
struct SessionDiffCtx {
  sqlite3_stmt *pStmt;
  int nOldOff;
};

/*
** The diff hook implementations.
*/
static int sessionDiffOld(void *pCtx, int iVal, sqlite3_value **ppVal){
  SessionDiffCtx *p = (SessionDiffCtx*)pCtx;
  *ppVal = sqlite3_column_value(p->pStmt, iVal+p->nOldOff);
  return SQLITE_OK;
}
static int sessionDiffNew(void *pCtx, int iVal, sqlite3_value **ppVal){
  SessionDiffCtx *p = (SessionDiffCtx*)pCtx;
  *ppVal = sqlite3_column_value(p->pStmt, iVal);
   return SQLITE_OK;
}
static int sessionDiffCount(void *pCtx){
  SessionDiffCtx *p = (SessionDiffCtx*)pCtx;
  return p->nOldOff ? p->nOldOff : sqlite3_column_count(p->pStmt);
}
static int sessionDiffDepth(void *pCtx){
  return 0;
}

/*
** Install the diff hooks on the session object passed as the only
** argument.
*/
static void sessionDiffHooks(
  sqlite3_session *pSession,
  SessionDiffCtx *pDiffCtx
){
  pSession->hook.pCtx = (void*)pDiffCtx;
  pSession->hook.xOld = sessionDiffOld;
  pSession->hook.xNew = sessionDiffNew;
  pSession->hook.xCount = sessionDiffCount;
  pSession->hook.xDepth = sessionDiffDepth;
}

static char *sessionExprComparePK(
  int nCol,
  const char *zDb1, const char *zDb2, 
  const char *zTab,
  const char **azCol, u8 *abPK
){
  int i;
  const char *zSep = "";
  char *zRet = 0;

  for(i=0; i<nCol; i++){
    if( abPK[i] ){
      zRet = sqlite3_mprintf("%z%s\"%w\".\"%w\".\"%w\"=\"%w\".\"%w\".\"%w\"",
          zRet, zSep, zDb1, zTab, azCol[i], zDb2, zTab, azCol[i]
      );
      zSep = " AND ";
      if( zRet==0 ) break;
    }
  }

  return zRet;
}

static char *sessionExprCompareOther(
  int nCol,
  const char *zDb1, const char *zDb2, 
  const char *zTab,
  const char **azCol, u8 *abPK
){
  int i;
  const char *zSep = "";
  char *zRet = 0;
  int bHave = 0;

  for(i=0; i<nCol; i++){
    if( abPK[i]==0 ){
      bHave = 1;
      zRet = sqlite3_mprintf(
          "%z%s\"%w\".\"%w\".\"%w\" IS NOT \"%w\".\"%w\".\"%w\"",
          zRet, zSep, zDb1, zTab, azCol[i], zDb2, zTab, azCol[i]
      );
      zSep = " OR ";
      if( zRet==0 ) break;
    }
  }

  if( bHave==0 ){
    assert( zRet==0 );
    zRet = sqlite3_mprintf("0");
  }

  return zRet;
}

static char *sessionSelectFindNew(
  int nCol,
  const char *zDb1,      /* Pick rows in this db only */
  const char *zDb2,      /* But not in this one */
  const char *zTbl,      /* Table name */
  const char *zExpr
){
  char *zRet = sqlite3_mprintf(
      "SELECT * FROM \"%w\".\"%w\" WHERE NOT EXISTS ("
      "  SELECT 1 FROM \"%w\".\"%w\" WHERE %s"
      ")",
      zDb1, zTbl, zDb2, zTbl, zExpr
  );
  return zRet;
}

static int sessionDiffFindNew(
  int op,
  sqlite3_session *pSession,
  SessionTable *pTab,
  const char *zDb1,
  const char *zDb2,
  char *zExpr
){
  int rc = SQLITE_OK;
  char *zStmt = sessionSelectFindNew(pTab->nCol, zDb1, zDb2, pTab->zName,zExpr);

  if( zStmt==0 ){
    rc = SQLITE_NOMEM;
  }else{
    sqlite3_stmt *pStmt;
    rc = sqlite3_prepare(pSession->db, zStmt, -1, &pStmt, 0);
    if( rc==SQLITE_OK ){
      SessionDiffCtx *pDiffCtx = (SessionDiffCtx*)pSession->hook.pCtx;
      pDiffCtx->pStmt = pStmt;
      pDiffCtx->nOldOff = 0;
      while( SQLITE_ROW==sqlite3_step(pStmt) ){
        sessionPreupdateOneChange(op, pSession, pTab);
      }
      rc = sqlite3_finalize(pStmt);
    }
    sqlite3_free(zStmt);
  }

  return rc;
}

static int sessionDiffFindModified(
  sqlite3_session *pSession, 
  SessionTable *pTab, 
  const char *zFrom, 
  const char *zExpr
){
  int rc = SQLITE_OK;

  char *zExpr2 = sessionExprCompareOther(pTab->nCol,
      pSession->zDb, zFrom, pTab->zName, pTab->azCol, pTab->abPK
  );
  if( zExpr2==0 ){
    rc = SQLITE_NOMEM;
  }else{
    char *zStmt = sqlite3_mprintf(
        "SELECT * FROM \"%w\".\"%w\", \"%w\".\"%w\" WHERE %s AND (%z)",
        pSession->zDb, pTab->zName, zFrom, pTab->zName, zExpr, zExpr2
    );
    if( zStmt==0 ){
      rc = SQLITE_NOMEM;
    }else{
      sqlite3_stmt *pStmt;
      rc = sqlite3_prepare(pSession->db, zStmt, -1, &pStmt, 0);

      if( rc==SQLITE_OK ){
        SessionDiffCtx *pDiffCtx = (SessionDiffCtx*)pSession->hook.pCtx;
        pDiffCtx->pStmt = pStmt;
        pDiffCtx->nOldOff = pTab->nCol;
        while( SQLITE_ROW==sqlite3_step(pStmt) ){
          sessionPreupdateOneChange(SQLITE_UPDATE, pSession, pTab);
        }
        rc = sqlite3_finalize(pStmt);
      }
      sqlite3_free(zStmt);
    }
  }

  return rc;
}

SQLITE_API int SQLITE_STDCALL sqlite3session_diff(
  sqlite3_session *pSession,
  const char *zFrom,
  const char *zTbl,
  char **pzErrMsg
){
  const char *zDb = pSession->zDb;
  int rc = pSession->rc;
  SessionDiffCtx d;

  memset(&d, 0, sizeof(d));
  sessionDiffHooks(pSession, &d);

  sqlite3_mutex_enter(sqlite3_db_mutex(pSession->db));
  if( pzErrMsg ) *pzErrMsg = 0;
  if( rc==SQLITE_OK ){
    char *zExpr = 0;
    sqlite3 *db = pSession->db;
    SessionTable *pTo;            /* Table zTbl */

    /* Locate and if necessary initialize the target table object */
    rc = sessionFindTable(pSession, zTbl, &pTo);
    if( pTo==0 ) goto diff_out;
    if( sessionInitTable(pSession, pTo) ){
      rc = pSession->rc;
      goto diff_out;
    }

    /* Check the table schemas match */
    if( rc==SQLITE_OK ){
      int bHasPk = 0;
      int bMismatch = 0;
      int nCol;                   /* Columns in zFrom.zTbl */
      u8 *abPK;
      const char **azCol = 0;
      rc = sessionTableInfo(db, zFrom, zTbl, &nCol, 0, &azCol, &abPK);
      if( rc==SQLITE_OK ){
        if( pTo->nCol!=nCol ){
          bMismatch = 1;
        }else{
          int i;
          for(i=0; i<nCol; i++){
            if( pTo->abPK[i]!=abPK[i] ) bMismatch = 1;
            if( sqlite3_stricmp(azCol[i], pTo->azCol[i]) ) bMismatch = 1;
            if( abPK[i] ) bHasPk = 1;
          }
        }

      }
      sqlite3_free((char*)azCol);
      if( bMismatch ){
        *pzErrMsg = sqlite3_mprintf("table schemas do not match");
        rc = SQLITE_SCHEMA;
      }
      if( bHasPk==0 ){
        /* Ignore tables with no primary keys */
        goto diff_out;
      }
    }

    if( rc==SQLITE_OK ){
      zExpr = sessionExprComparePK(pTo->nCol, 
          zDb, zFrom, pTo->zName, pTo->azCol, pTo->abPK
      );
    }

    /* Find new rows */
    if( rc==SQLITE_OK ){
      rc = sessionDiffFindNew(SQLITE_INSERT, pSession, pTo, zDb, zFrom, zExpr);
    }

    /* Find old rows */
    if( rc==SQLITE_OK ){
      rc = sessionDiffFindNew(SQLITE_DELETE, pSession, pTo, zFrom, zDb, zExpr);
    }

    /* Find modified rows */
    if( rc==SQLITE_OK ){
      rc = sessionDiffFindModified(pSession, pTo, zFrom, zExpr);
    }

    sqlite3_free(zExpr);
  }

 diff_out:
  sessionPreupdateHooks(pSession);
  sqlite3_mutex_leave(sqlite3_db_mutex(pSession->db));
  return rc;
}

/*
** Create a session object. This session object will record changes to
** database zDb attached to connection db.
*/
SQLITE_API int SQLITE_STDCALL sqlite3session_create(
  sqlite3 *db,                    /* Database handle */
  const char *zDb,                /* Name of db (e.g. "main") */
  sqlite3_session **ppSession     /* OUT: New session object */
){
  sqlite3_session *pNew;          /* Newly allocated session object */
  sqlite3_session *pOld;          /* Session object already attached to db */
  int nDb = sqlite3Strlen30(zDb); /* Length of zDb in bytes */

  /* Zero the output value in case an error occurs. */
  *ppSession = 0;

  /* Allocate and populate the new session object. */
  pNew = (sqlite3_session *)sqlite3_malloc(sizeof(sqlite3_session) + nDb + 1);
  if( !pNew ) return SQLITE_NOMEM;
  memset(pNew, 0, sizeof(sqlite3_session));
  pNew->db = db;
  pNew->zDb = (char *)&pNew[1];
  pNew->bEnable = 1;
  memcpy(pNew->zDb, zDb, nDb+1);
  sessionPreupdateHooks(pNew);

  /* Add the new session object to the linked list of session objects 
  ** attached to database handle $db. Do this under the cover of the db
  ** handle mutex.  */
  sqlite3_mutex_enter(sqlite3_db_mutex(db));
  pOld = (sqlite3_session*)sqlite3_preupdate_hook(db, xPreUpdate, (void*)pNew);
  pNew->pNext = pOld;
  sqlite3_mutex_leave(sqlite3_db_mutex(db));

  *ppSession = pNew;
  return SQLITE_OK;
}

/*
** Free the list of table objects passed as the first argument. The contents
** of the changed-rows hash tables are also deleted.
*/
static void sessionDeleteTable(SessionTable *pList){
  SessionTable *pNext;
  SessionTable *pTab;

  for(pTab=pList; pTab; pTab=pNext){
    int i;
    pNext = pTab->pNext;
    for(i=0; i<pTab->nChange; i++){
      SessionChange *p;
      SessionChange *pNext;
      for(p=pTab->apChange[i]; p; p=pNext){
        pNext = p->pNext;
        sqlite3_free(p);
      }
    }
    sqlite3_free((char*)pTab->azCol);  /* cast works around VC++ bug */
    sqlite3_free(pTab->apChange);
    sqlite3_free(pTab);
  }
}

/*
** Delete a session object previously allocated using sqlite3session_create().
*/
SQLITE_API void SQLITE_STDCALL sqlite3session_delete(sqlite3_session *pSession){
  sqlite3 *db = pSession->db;
  sqlite3_session *pHead;
  sqlite3_session **pp;

  /* Unlink the session from the linked list of sessions attached to the
  ** database handle. Hold the db mutex while doing so.  */
  sqlite3_mutex_enter(sqlite3_db_mutex(db));
  pHead = (sqlite3_session*)sqlite3_preupdate_hook(db, 0, 0);
  for(pp=&pHead; ALWAYS((*pp)!=0); pp=&((*pp)->pNext)){
    if( (*pp)==pSession ){
      *pp = (*pp)->pNext;
      if( pHead ) sqlite3_preupdate_hook(db, xPreUpdate, (void*)pHead);
      break;
    }
  }
  sqlite3_mutex_leave(sqlite3_db_mutex(db));

  /* Delete all attached table objects. And the contents of their 
  ** associated hash-tables. */
  sessionDeleteTable(pSession->pTable);

  /* Free the session object itself. */
  sqlite3_free(pSession);
}

/*
** Set a table filter on a Session Object.
*/
SQLITE_API void SQLITE_STDCALL sqlite3session_table_filter(
  sqlite3_session *pSession, 
  int(*xFilter)(void*, const char*),
  void *pCtx                      /* First argument passed to xFilter */
){
  pSession->bAutoAttach = 1;
  pSession->pFilterCtx = pCtx;
  pSession->xTableFilter = xFilter;
}

/*
** Attach a table to a session. All subsequent changes made to the table
** while the session object is enabled will be recorded.
**
** Only tables that have a PRIMARY KEY defined may be attached. It does
** not matter if the PRIMARY KEY is an "INTEGER PRIMARY KEY" (rowid alias)
** or not.
*/
SQLITE_API int SQLITE_STDCALL sqlite3session_attach(
  sqlite3_session *pSession,      /* Session object */
  const char *zName               /* Table name */
){
  int rc = SQLITE_OK;
  sqlite3_mutex_enter(sqlite3_db_mutex(pSession->db));

  if( !zName ){
    pSession->bAutoAttach = 1;
  }else{
    SessionTable *pTab;           /* New table object (if required) */
    int nName;                    /* Number of bytes in string zName */

    /* First search for an existing entry. If one is found, this call is
    ** a no-op. Return early. */
    nName = sqlite3Strlen30(zName);
    for(pTab=pSession->pTable; pTab; pTab=pTab->pNext){
      if( 0==sqlite3_strnicmp(pTab->zName, zName, nName+1) ) break;
    }

    if( !pTab ){
      /* Allocate new SessionTable object. */
      pTab = (SessionTable *)sqlite3_malloc(sizeof(SessionTable) + nName + 1);
      if( !pTab ){
        rc = SQLITE_NOMEM;
      }else{
        /* Populate the new SessionTable object and link it into the list.
        ** The new object must be linked onto the end of the list, not 
        ** simply added to the start of it in order to ensure that tables
        ** appear in the correct order when a changeset or patchset is
        ** eventually generated. */
        SessionTable **ppTab;
        memset(pTab, 0, sizeof(SessionTable));
        pTab->zName = (char *)&pTab[1];
        memcpy(pTab->zName, zName, nName+1);
        for(ppTab=&pSession->pTable; *ppTab; ppTab=&(*ppTab)->pNext);
        *ppTab = pTab;
      }
    }
  }

  sqlite3_mutex_leave(sqlite3_db_mutex(pSession->db));
  return rc;
}

/*
** Ensure that there is room in the buffer to append nByte bytes of data.
** If not, use sqlite3_realloc() to grow the buffer so that there is.
**
** If successful, return zero. Otherwise, if an OOM condition is encountered,
** set *pRc to SQLITE_NOMEM and return non-zero.
*/
static int sessionBufferGrow(SessionBuffer *p, int nByte, int *pRc){
  if( *pRc==SQLITE_OK && p->nAlloc-p->nBuf<nByte ){
    u8 *aNew;
    int nNew = p->nAlloc ? p->nAlloc : 128;
    do {
      nNew = nNew*2;
    }while( nNew<(p->nBuf+nByte) );

    aNew = (u8 *)sqlite3_realloc(p->aBuf, nNew);
    if( 0==aNew ){
      *pRc = SQLITE_NOMEM;
    }else{
      p->aBuf = aNew;
      p->nAlloc = nNew;
    }
  }
  return (*pRc!=SQLITE_OK);
}

/*
** Append the value passed as the second argument to the buffer passed
** as the first.
**
** This function is a no-op if *pRc is non-zero when it is called.
** Otherwise, if an error occurs, *pRc is set to an SQLite error code
** before returning.
*/
static void sessionAppendValue(SessionBuffer *p, sqlite3_value *pVal, int *pRc){
  int rc = *pRc;
  if( rc==SQLITE_OK ){
    int nByte = 0;
    rc = sessionSerializeValue(0, pVal, &nByte);
    sessionBufferGrow(p, nByte, &rc);
    if( rc==SQLITE_OK ){
      rc = sessionSerializeValue(&p->aBuf[p->nBuf], pVal, 0);
      p->nBuf += nByte;
    }else{
      *pRc = rc;
    }
  }
}

/*
** This function is a no-op if *pRc is other than SQLITE_OK when it is 
** called. Otherwise, append a single byte to the buffer. 
**
** If an OOM condition is encountered, set *pRc to SQLITE_NOMEM before
** returning.
*/
static void sessionAppendByte(SessionBuffer *p, u8 v, int *pRc){
  if( 0==sessionBufferGrow(p, 1, pRc) ){
    p->aBuf[p->nBuf++] = v;
  }
}

/*
** This function is a no-op if *pRc is other than SQLITE_OK when it is 
** called. Otherwise, append a single varint to the buffer. 
**
** If an OOM condition is encountered, set *pRc to SQLITE_NOMEM before
** returning.
*/
static void sessionAppendVarint(SessionBuffer *p, int v, int *pRc){
  if( 0==sessionBufferGrow(p, 9, pRc) ){
    p->nBuf += sessionVarintPut(&p->aBuf[p->nBuf], v);
  }
}

/*
** This function is a no-op if *pRc is other than SQLITE_OK when it is 
** called. Otherwise, append a blob of data to the buffer. 
**
** If an OOM condition is encountered, set *pRc to SQLITE_NOMEM before
** returning.
*/
static void sessionAppendBlob(
  SessionBuffer *p, 
  const u8 *aBlob, 
  int nBlob, 
  int *pRc
){
  if( 0==sessionBufferGrow(p, nBlob, pRc) ){
    memcpy(&p->aBuf[p->nBuf], aBlob, nBlob);
    p->nBuf += nBlob;
  }
}

/*
** This function is a no-op if *pRc is other than SQLITE_OK when it is 
** called. Otherwise, append a string to the buffer. All bytes in the string
** up to (but not including) the nul-terminator are written to the buffer.
**
** If an OOM condition is encountered, set *pRc to SQLITE_NOMEM before
** returning.
*/
static void sessionAppendStr(
  SessionBuffer *p, 
  const char *zStr, 
  int *pRc
){
  int nStr = sqlite3Strlen30(zStr);
  if( 0==sessionBufferGrow(p, nStr, pRc) ){
    memcpy(&p->aBuf[p->nBuf], zStr, nStr);
    p->nBuf += nStr;
  }
}

/*
** This function is a no-op if *pRc is other than SQLITE_OK when it is 
** called. Otherwise, append the string representation of integer iVal
** to the buffer. No nul-terminator is written.
**
** If an OOM condition is encountered, set *pRc to SQLITE_NOMEM before
** returning.
*/
static void sessionAppendInteger(
  SessionBuffer *p,               /* Buffer to append to */
  int iVal,                       /* Value to write the string rep. of */
  int *pRc                        /* IN/OUT: Error code */
){
  char aBuf[24];
  sqlite3_snprintf(sizeof(aBuf)-1, aBuf, "%d", iVal);
  sessionAppendStr(p, aBuf, pRc);
}

/*
** This function is a no-op if *pRc is other than SQLITE_OK when it is 
** called. Otherwise, append the string zStr enclosed in quotes (") and
** with any embedded quote characters escaped to the buffer. No 
** nul-terminator byte is written.
**
** If an OOM condition is encountered, set *pRc to SQLITE_NOMEM before
** returning.
*/
static void sessionAppendIdent(
  SessionBuffer *p,               /* Buffer to a append to */
  const char *zStr,               /* String to quote, escape and append */
  int *pRc                        /* IN/OUT: Error code */
){
  int nStr = sqlite3Strlen30(zStr)*2 + 2 + 1;
  if( 0==sessionBufferGrow(p, nStr, pRc) ){
    char *zOut = (char *)&p->aBuf[p->nBuf];
    const char *zIn = zStr;
    *zOut++ = '"';
    while( *zIn ){
      if( *zIn=='"' ) *zOut++ = '"';
      *zOut++ = *(zIn++);
    }
    *zOut++ = '"';
    p->nBuf = (int)((u8 *)zOut - p->aBuf);
  }
}

/*
** This function is a no-op if *pRc is other than SQLITE_OK when it is
** called. Otherwse, it appends the serialized version of the value stored
** in column iCol of the row that SQL statement pStmt currently points
** to to the buffer.
*/
static void sessionAppendCol(
  SessionBuffer *p,               /* Buffer to append to */
  sqlite3_stmt *pStmt,            /* Handle pointing to row containing value */
  int iCol,                       /* Column to read value from */
  int *pRc                        /* IN/OUT: Error code */
){
  if( *pRc==SQLITE_OK ){
    int eType = sqlite3_column_type(pStmt, iCol);
    sessionAppendByte(p, (u8)eType, pRc);
    if( eType==SQLITE_INTEGER || eType==SQLITE_FLOAT ){
      sqlite3_int64 i;
      u8 aBuf[8];
      if( eType==SQLITE_INTEGER ){
        i = sqlite3_column_int64(pStmt, iCol);
      }else{
        double r = sqlite3_column_double(pStmt, iCol);
        memcpy(&i, &r, 8);
      }
      sessionPutI64(aBuf, i);
      sessionAppendBlob(p, aBuf, 8, pRc);
    }
    if( eType==SQLITE_BLOB || eType==SQLITE_TEXT ){
      u8 *z;
      int nByte;
      if( eType==SQLITE_BLOB ){
        z = (u8 *)sqlite3_column_blob(pStmt, iCol);
      }else{
        z = (u8 *)sqlite3_column_text(pStmt, iCol);
      }
      nByte = sqlite3_column_bytes(pStmt, iCol);
      if( z || (eType==SQLITE_BLOB && nByte==0) ){
        sessionAppendVarint(p, nByte, pRc);
        sessionAppendBlob(p, z, nByte, pRc);
      }else{
        *pRc = SQLITE_NOMEM;
      }
    }
  }
}

/*
**
** This function appends an update change to the buffer (see the comments 
** under "CHANGESET FORMAT" at the top of the file). An update change 
** consists of:
**
**   1 byte:  SQLITE_UPDATE (0x17)
**   n bytes: old.* record (see RECORD FORMAT)
**   m bytes: new.* record (see RECORD FORMAT)
**
** The SessionChange object passed as the third argument contains the
** values that were stored in the row when the session began (the old.*
** values). The statement handle passed as the second argument points
** at the current version of the row (the new.* values).
**
** If all of the old.* values are equal to their corresponding new.* value
** (i.e. nothing has changed), then no data at all is appended to the buffer.
**
** Otherwise, the old.* record contains all primary key values and the 
** original values of any fields that have been modified. The new.* record 
** contains the new values of only those fields that have been modified.
*/ 
static int sessionAppendUpdate(
  SessionBuffer *pBuf,            /* Buffer to append to */
  int bPatchset,                  /* True for "patchset", 0 for "changeset" */
  sqlite3_stmt *pStmt,            /* Statement handle pointing at new row */
  SessionChange *p,               /* Object containing old values */
  u8 *abPK                        /* Boolean array - true for PK columns */
){
  int rc = SQLITE_OK;
  SessionBuffer buf2 = {0,0,0}; /* Buffer to accumulate new.* record in */
  int bNoop = 1;                /* Set to zero if any values are modified */
  int nRewind = pBuf->nBuf;     /* Set to zero if any values are modified */
  int i;                        /* Used to iterate through columns */
  u8 *pCsr = p->aRecord;        /* Used to iterate through old.* values */

  sessionAppendByte(pBuf, SQLITE_UPDATE, &rc);
  sessionAppendByte(pBuf, p->bIndirect, &rc);
  for(i=0; i<sqlite3_column_count(pStmt); i++){
    int bChanged = 0;
    int nAdvance;
    int eType = *pCsr;
    switch( eType ){
      case SQLITE_NULL:
        nAdvance = 1;
        if( sqlite3_column_type(pStmt, i)!=SQLITE_NULL ){
          bChanged = 1;
        }
        break;

      case SQLITE_FLOAT:
      case SQLITE_INTEGER: {
        nAdvance = 9;
        if( eType==sqlite3_column_type(pStmt, i) ){
          sqlite3_int64 iVal = sessionGetI64(&pCsr[1]);
          if( eType==SQLITE_INTEGER ){
            if( iVal==sqlite3_column_int64(pStmt, i) ) break;
          }else{
            double dVal;
            memcpy(&dVal, &iVal, 8);
            if( dVal==sqlite3_column_double(pStmt, i) ) break;
          }
        }
        bChanged = 1;
        break;
      }

      default: {
        int nByte;
        int nHdr = 1 + sessionVarintGet(&pCsr[1], &nByte);
        assert( eType==SQLITE_TEXT || eType==SQLITE_BLOB );
        nAdvance = nHdr + nByte;
        if( eType==sqlite3_column_type(pStmt, i) 
         && nByte==sqlite3_column_bytes(pStmt, i) 
         && 0==memcmp(&pCsr[nHdr], sqlite3_column_blob(pStmt, i), nByte)
        ){
          break;
        }
        bChanged = 1;
      }
    }

    /* If at least one field has been modified, this is not a no-op. */
    if( bChanged ) bNoop = 0;

    /* Add a field to the old.* record. This is omitted if this modules is
    ** currently generating a patchset. */
    if( bPatchset==0 ){
      if( bChanged || abPK[i] ){
        sessionAppendBlob(pBuf, pCsr, nAdvance, &rc);
      }else{
        sessionAppendByte(pBuf, 0, &rc);
      }
    }

    /* Add a field to the new.* record. Or the only record if currently
    ** generating a patchset.  */
    if( bChanged || (bPatchset && abPK[i]) ){
      sessionAppendCol(&buf2, pStmt, i, &rc);
    }else{
      sessionAppendByte(&buf2, 0, &rc);
    }

    pCsr += nAdvance;
  }

  if( bNoop ){
    pBuf->nBuf = nRewind;
  }else{
    sessionAppendBlob(pBuf, buf2.aBuf, buf2.nBuf, &rc);
  }
  sqlite3_free(buf2.aBuf);

  return rc;
}

/*
** Append a DELETE change to the buffer passed as the first argument. Use
** the changeset format if argument bPatchset is zero, or the patchset
** format otherwise.
*/
static int sessionAppendDelete(
  SessionBuffer *pBuf,            /* Buffer to append to */
  int bPatchset,                  /* True for "patchset", 0 for "changeset" */
  SessionChange *p,               /* Object containing old values */
  int nCol,                       /* Number of columns in table */
  u8 *abPK                        /* Boolean array - true for PK columns */
){
  int rc = SQLITE_OK;

  sessionAppendByte(pBuf, SQLITE_DELETE, &rc);
  sessionAppendByte(pBuf, p->bIndirect, &rc);

  if( bPatchset==0 ){
    sessionAppendBlob(pBuf, p->aRecord, p->nRecord, &rc);
  }else{
    int i;
    u8 *a = p->aRecord;
    for(i=0; i<nCol; i++){
      u8 *pStart = a;
      int eType = *a++;

      switch( eType ){
        case 0:
        case SQLITE_NULL:
          assert( abPK[i]==0 );
          break;

        case SQLITE_FLOAT:
        case SQLITE_INTEGER:
          a += 8;
          break;

        default: {
          int n;
          a += sessionVarintGet(a, &n);
          a += n;
          break;
        }
      }
      if( abPK[i] ){
        sessionAppendBlob(pBuf, pStart, (int)(a-pStart), &rc);
      }
    }
    assert( (a - p->aRecord)==p->nRecord );
  }

  return rc;
}

/*
** Formulate and prepare a SELECT statement to retrieve a row from table
** zTab in database zDb based on its primary key. i.e.
**
**   SELECT * FROM zDb.zTab WHERE pk1 = ? AND pk2 = ? AND ...
*/
static int sessionSelectStmt(
  sqlite3 *db,                    /* Database handle */
  const char *zDb,                /* Database name */
  const char *zTab,               /* Table name */
  int nCol,                       /* Number of columns in table */
  const char **azCol,             /* Names of table columns */
  u8 *abPK,                       /* PRIMARY KEY  array */
  sqlite3_stmt **ppStmt           /* OUT: Prepared SELECT statement */
){
  int rc = SQLITE_OK;
  int i;
  const char *zSep = "";
  SessionBuffer buf = {0, 0, 0};

  sessionAppendStr(&buf, "SELECT * FROM ", &rc);
  sessionAppendIdent(&buf, zDb, &rc);
  sessionAppendStr(&buf, ".", &rc);
  sessionAppendIdent(&buf, zTab, &rc);
  sessionAppendStr(&buf, " WHERE ", &rc);
  for(i=0; i<nCol; i++){
    if( abPK[i] ){
      sessionAppendStr(&buf, zSep, &rc);
      sessionAppendIdent(&buf, azCol[i], &rc);
      sessionAppendStr(&buf, " = ?", &rc);
      sessionAppendInteger(&buf, i+1, &rc);
      zSep = " AND ";
    }
  }
  if( rc==SQLITE_OK ){
    rc = sqlite3_prepare_v2(db, (char *)buf.aBuf, buf.nBuf, ppStmt, 0);
  }
  sqlite3_free(buf.aBuf);
  return rc;
}

/*
** Bind the PRIMARY KEY values from the change passed in argument pChange
** to the SELECT statement passed as the first argument. The SELECT statement
** is as prepared by function sessionSelectStmt().
**
** Return SQLITE_OK if all PK values are successfully bound, or an SQLite
** error code (e.g. SQLITE_NOMEM) otherwise.
*/
static int sessionSelectBind(
  sqlite3_stmt *pSelect,          /* SELECT from sessionSelectStmt() */
  int nCol,                       /* Number of columns in table */
  u8 *abPK,                       /* PRIMARY KEY array */
  SessionChange *pChange          /* Change structure */
){
  int i;
  int rc = SQLITE_OK;
  u8 *a = pChange->aRecord;

  for(i=0; i<nCol && rc==SQLITE_OK; i++){
    int eType = *a++;

    switch( eType ){
      case 0:
      case SQLITE_NULL:
        assert( abPK[i]==0 );
        break;

      case SQLITE_INTEGER: {
        if( abPK[i] ){
          i64 iVal = sessionGetI64(a);
          rc = sqlite3_bind_int64(pSelect, i+1, iVal);
        }
        a += 8;
        break;
      }

      case SQLITE_FLOAT: {
        if( abPK[i] ){
          double rVal;
          i64 iVal = sessionGetI64(a);
          memcpy(&rVal, &iVal, 8);
          rc = sqlite3_bind_double(pSelect, i+1, rVal);
        }
        a += 8;
        break;
      }

      case SQLITE_TEXT: {
        int n;
        a += sessionVarintGet(a, &n);
        if( abPK[i] ){
          rc = sqlite3_bind_text(pSelect, i+1, (char *)a, n, SQLITE_TRANSIENT);
        }
        a += n;
        break;
      }

      default: {
        int n;
        assert( eType==SQLITE_BLOB );
        a += sessionVarintGet(a, &n);
        if( abPK[i] ){
          rc = sqlite3_bind_blob(pSelect, i+1, a, n, SQLITE_TRANSIENT);
        }
        a += n;
        break;
      }
    }
  }

  return rc;
}

/*
** This function is a no-op if *pRc is set to other than SQLITE_OK when it
** is called. Otherwise, append a serialized table header (part of the binary 
** changeset format) to buffer *pBuf. If an error occurs, set *pRc to an
** SQLite error code before returning.
*/
static void sessionAppendTableHdr(
  SessionBuffer *pBuf,            /* Append header to this buffer */
  int bPatchset,                  /* Use the patchset format if true */
  SessionTable *pTab,             /* Table object to append header for */
  int *pRc                        /* IN/OUT: Error code */
){
  /* Write a table header */
  sessionAppendByte(pBuf, (bPatchset ? 'P' : 'T'), pRc);
  sessionAppendVarint(pBuf, pTab->nCol, pRc);
  sessionAppendBlob(pBuf, pTab->abPK, pTab->nCol, pRc);
  sessionAppendBlob(pBuf, (u8 *)pTab->zName, (int)strlen(pTab->zName)+1, pRc);
}

/*
** Generate either a changeset (if argument bPatchset is zero) or a patchset
** (if it is non-zero) based on the current contents of the session object
** passed as the first argument.
**
** If no error occurs, SQLITE_OK is returned and the new changeset/patchset
** stored in output variables *pnChangeset and *ppChangeset. Or, if an error
** occurs, an SQLite error code is returned and both output variables set 
** to 0.
*/
static int sessionGenerateChangeset(
  sqlite3_session *pSession,      /* Session object */
  int bPatchset,                  /* True for patchset, false for changeset */
  int (*xOutput)(void *pOut, const void *pData, int nData),
  void *pOut,                     /* First argument for xOutput */
  int *pnChangeset,               /* OUT: Size of buffer at *ppChangeset */
  void **ppChangeset              /* OUT: Buffer containing changeset */
){
  sqlite3 *db = pSession->db;     /* Source database handle */
  SessionTable *pTab;             /* Used to iterate through attached tables */
  SessionBuffer buf = {0,0,0};    /* Buffer in which to accumlate changeset */
  int rc;                         /* Return code */

  assert( xOutput==0 || (pnChangeset==0 && ppChangeset==0 ) );

  /* Zero the output variables in case an error occurs. If this session
  ** object is already in the error state (sqlite3_session.rc != SQLITE_OK),
  ** this call will be a no-op.  */
  if( xOutput==0 ){
    *pnChangeset = 0;
    *ppChangeset = 0;
  }

  if( pSession->rc ) return pSession->rc;
  rc = sqlite3_exec(pSession->db, "SAVEPOINT changeset", 0, 0, 0);
  if( rc!=SQLITE_OK ) return rc;

  sqlite3_mutex_enter(sqlite3_db_mutex(db));

  for(pTab=pSession->pTable; rc==SQLITE_OK && pTab; pTab=pTab->pNext){
    if( pTab->nEntry ){
      const char *zName = pTab->zName;
      int nCol;                   /* Number of columns in table */
      u8 *abPK;                   /* Primary key array */
      const char **azCol = 0;     /* Table columns */
      int i;                      /* Used to iterate through hash buckets */
      sqlite3_stmt *pSel = 0;     /* SELECT statement to query table pTab */
      int nRewind = buf.nBuf;     /* Initial size of write buffer */
      int nNoop;                  /* Size of buffer after writing tbl header */

      /* Check the table schema is still Ok. */
      rc = sessionTableInfo(db, pSession->zDb, zName, &nCol, 0, &azCol, &abPK);
      if( !rc && (pTab->nCol!=nCol || memcmp(abPK, pTab->abPK, nCol)) ){
        rc = SQLITE_SCHEMA;
      }

      /* Write a table header */
      sessionAppendTableHdr(&buf, bPatchset, pTab, &rc);

      /* Build and compile a statement to execute: */
      if( rc==SQLITE_OK ){
        rc = sessionSelectStmt(
            db, pSession->zDb, zName, nCol, azCol, abPK, &pSel);
      }

      nNoop = buf.nBuf;
      for(i=0; i<pTab->nChange && rc==SQLITE_OK; i++){
        SessionChange *p;         /* Used to iterate through changes */

        for(p=pTab->apChange[i]; rc==SQLITE_OK && p; p=p->pNext){
          rc = sessionSelectBind(pSel, nCol, abPK, p);
          if( rc!=SQLITE_OK ) continue;
          if( sqlite3_step(pSel)==SQLITE_ROW ){
            if( p->op==SQLITE_INSERT ){
              int iCol;
              sessionAppendByte(&buf, SQLITE_INSERT, &rc);
              sessionAppendByte(&buf, p->bIndirect, &rc);
              for(iCol=0; iCol<nCol; iCol++){
                sessionAppendCol(&buf, pSel, iCol, &rc);
              }
            }else{
              rc = sessionAppendUpdate(&buf, bPatchset, pSel, p, abPK);
            }
          }else if( p->op!=SQLITE_INSERT ){
            rc = sessionAppendDelete(&buf, bPatchset, p, nCol, abPK);
          }
          if( rc==SQLITE_OK ){
            rc = sqlite3_reset(pSel);
          }

          /* If the buffer is now larger than SESSIONS_STRM_CHUNK_SIZE, pass
          ** its contents to the xOutput() callback. */
          if( xOutput 
           && rc==SQLITE_OK 
           && buf.nBuf>nNoop 
           && buf.nBuf>SESSIONS_STRM_CHUNK_SIZE 
          ){
            rc = xOutput(pOut, (void*)buf.aBuf, buf.nBuf);
            nNoop = -1;
            buf.nBuf = 0;
          }

        }
      }

      sqlite3_finalize(pSel);
      if( buf.nBuf==nNoop ){
        buf.nBuf = nRewind;
      }
      sqlite3_free((char*)azCol);  /* cast works around VC++ bug */
    }
  }

  if( rc==SQLITE_OK ){
    if( xOutput==0 ){
      *pnChangeset = buf.nBuf;
      *ppChangeset = buf.aBuf;
      buf.aBuf = 0;
    }else if( buf.nBuf>0 ){
      rc = xOutput(pOut, (void*)buf.aBuf, buf.nBuf);
    }
  }

  sqlite3_free(buf.aBuf);
  sqlite3_exec(db, "RELEASE changeset", 0, 0, 0);
  sqlite3_mutex_leave(sqlite3_db_mutex(db));
  return rc;
}

/*
** Obtain a changeset object containing all changes recorded by the 
** session object passed as the first argument.
**
** It is the responsibility of the caller to eventually free the buffer 
** using sqlite3_free().
*/
SQLITE_API int SQLITE_STDCALL sqlite3session_changeset(
  sqlite3_session *pSession,      /* Session object */
  int *pnChangeset,               /* OUT: Size of buffer at *ppChangeset */
  void **ppChangeset              /* OUT: Buffer containing changeset */
){
  return sessionGenerateChangeset(pSession, 0, 0, 0, pnChangeset, ppChangeset);
}

/*
** Streaming version of sqlite3session_changeset().
*/
SQLITE_API int SQLITE_STDCALL sqlite3session_changeset_strm(
  sqlite3_session *pSession,
  int (*xOutput)(void *pOut, const void *pData, int nData),
  void *pOut
){
  return sessionGenerateChangeset(pSession, 0, xOutput, pOut, 0, 0);
}

/*
** Streaming version of sqlite3session_patchset().
*/
SQLITE_API int SQLITE_STDCALL sqlite3session_patchset_strm(
  sqlite3_session *pSession,
  int (*xOutput)(void *pOut, const void *pData, int nData),
  void *pOut
){
  return sessionGenerateChangeset(pSession, 1, xOutput, pOut, 0, 0);
}

/*
** Obtain a patchset object containing all changes recorded by the 
** session object passed as the first argument.
**
** It is the responsibility of the caller to eventually free the buffer 
** using sqlite3_free().
*/
SQLITE_API int SQLITE_STDCALL sqlite3session_patchset(
  sqlite3_session *pSession,      /* Session object */
  int *pnPatchset,                /* OUT: Size of buffer at *ppChangeset */
  void **ppPatchset               /* OUT: Buffer containing changeset */
){
  return sessionGenerateChangeset(pSession, 1, 0, 0, pnPatchset, ppPatchset);
}

/*
** Enable or disable the session object passed as the first argument.
*/
SQLITE_API int SQLITE_STDCALL sqlite3session_enable(sqlite3_session *pSession, int bEnable){
  int ret;
  sqlite3_mutex_enter(sqlite3_db_mutex(pSession->db));
  if( bEnable>=0 ){
    pSession->bEnable = bEnable;
  }
  ret = pSession->bEnable;
  sqlite3_mutex_leave(sqlite3_db_mutex(pSession->db));
  return ret;
}

/*
** Enable or disable the session object passed as the first argument.
*/
SQLITE_API int SQLITE_STDCALL sqlite3session_indirect(sqlite3_session *pSession, int bIndirect){
  int ret;
  sqlite3_mutex_enter(sqlite3_db_mutex(pSession->db));
  if( bIndirect>=0 ){
    pSession->bIndirect = bIndirect;
  }
  ret = pSession->bIndirect;
  sqlite3_mutex_leave(sqlite3_db_mutex(pSession->db));
  return ret;
}

/*
** Return true if there have been no changes to monitored tables recorded
** by the session object passed as the only argument.
*/
SQLITE_API int SQLITE_STDCALL sqlite3session_isempty(sqlite3_session *pSession){
  int ret = 0;
  SessionTable *pTab;

  sqlite3_mutex_enter(sqlite3_db_mutex(pSession->db));
  for(pTab=pSession->pTable; pTab && ret==0; pTab=pTab->pNext){
    ret = (pTab->nEntry>0);
  }
  sqlite3_mutex_leave(sqlite3_db_mutex(pSession->db));

  return (ret==0);
}

/*
** Do the work for either sqlite3changeset_start() or start_strm().
*/
static int sessionChangesetStart(
  sqlite3_changeset_iter **pp,    /* OUT: Changeset iterator handle */
  int (*xInput)(void *pIn, void *pData, int *pnData),
  void *pIn,
  int nChangeset,                 /* Size of buffer pChangeset in bytes */
  void *pChangeset                /* Pointer to buffer containing changeset */
){
  sqlite3_changeset_iter *pRet;   /* Iterator to return */
  int nByte;                      /* Number of bytes to allocate for iterator */

  assert( xInput==0 || (pChangeset==0 && nChangeset==0) );

  /* Zero the output variable in case an error occurs. */
  *pp = 0;

  /* Allocate and initialize the iterator structure. */
  nByte = sizeof(sqlite3_changeset_iter);
  pRet = (sqlite3_changeset_iter *)sqlite3_malloc(nByte);
  if( !pRet ) return SQLITE_NOMEM;
  memset(pRet, 0, sizeof(sqlite3_changeset_iter));
  pRet->in.aData = (u8 *)pChangeset;
  pRet->in.nData = nChangeset;
  pRet->in.xInput = xInput;
  pRet->in.pIn = pIn;
  pRet->in.bEof = (xInput ? 0 : 1);

  /* Populate the output variable and return success. */
  *pp = pRet;
  return SQLITE_OK;
}

/*
** Create an iterator used to iterate through the contents of a changeset.
*/
SQLITE_API int SQLITE_STDCALL sqlite3changeset_start(
  sqlite3_changeset_iter **pp,    /* OUT: Changeset iterator handle */
  int nChangeset,                 /* Size of buffer pChangeset in bytes */
  void *pChangeset                /* Pointer to buffer containing changeset */
){
  return sessionChangesetStart(pp, 0, 0, nChangeset, pChangeset);
}

/*
** Streaming version of sqlite3changeset_start().
*/
SQLITE_API int SQLITE_STDCALL sqlite3changeset_start_strm(
  sqlite3_changeset_iter **pp,    /* OUT: Changeset iterator handle */
  int (*xInput)(void *pIn, void *pData, int *pnData),
  void *pIn
){
  return sessionChangesetStart(pp, xInput, pIn, 0, 0);
}

/*
** If the SessionInput object passed as the only argument is a streaming
** object and the buffer is full, discard some data to free up space.
*/
static void sessionDiscardData(SessionInput *pIn){
  if( pIn->bEof && pIn->xInput && pIn->iNext>=SESSIONS_STRM_CHUNK_SIZE ){
    int nMove = pIn->buf.nBuf - pIn->iNext;
    assert( nMove>=0 );
    if( nMove>0 ){
      memmove(pIn->buf.aBuf, &pIn->buf.aBuf[pIn->iNext], nMove);
    }
    pIn->buf.nBuf -= pIn->iNext;
    pIn->iNext = 0;
    pIn->nData = pIn->buf.nBuf;
  }
}

/*
** Ensure that there are at least nByte bytes available in the buffer. Or,
** if there are not nByte bytes remaining in the input, that all available
** data is in the buffer.
**
** Return an SQLite error code if an error occurs, or SQLITE_OK otherwise.
*/
static int sessionInputBuffer(SessionInput *pIn, int nByte){
  int rc = SQLITE_OK;
  if( pIn->xInput ){
    while( !pIn->bEof && (pIn->iNext+nByte)>=pIn->nData && rc==SQLITE_OK ){
      int nNew = SESSIONS_STRM_CHUNK_SIZE;

      if( pIn->bNoDiscard==0 ) sessionDiscardData(pIn);
      if( SQLITE_OK==sessionBufferGrow(&pIn->buf, nNew, &rc) ){
        rc = pIn->xInput(pIn->pIn, &pIn->buf.aBuf[pIn->buf.nBuf], &nNew);
        if( nNew==0 ){
          pIn->bEof = 1;
        }else{
          pIn->buf.nBuf += nNew;
        }
      }

      pIn->aData = pIn->buf.aBuf;
      pIn->nData = pIn->buf.nBuf;
    }
  }
  return rc;
}

/*
** When this function is called, *ppRec points to the start of a record
** that contains nCol values. This function advances the pointer *ppRec
** until it points to the byte immediately following that record.
*/
static void sessionSkipRecord(
  u8 **ppRec,                     /* IN/OUT: Record pointer */
  int nCol                        /* Number of values in record */
){
  u8 *aRec = *ppRec;
  int i;
  for(i=0; i<nCol; i++){
    int eType = *aRec++;
    if( eType==SQLITE_TEXT || eType==SQLITE_BLOB ){
      int nByte;
      aRec += sessionVarintGet((u8*)aRec, &nByte);
      aRec += nByte;
    }else if( eType==SQLITE_INTEGER || eType==SQLITE_FLOAT ){
      aRec += 8;
    }
  }

  *ppRec = aRec;
}

/*
** This function sets the value of the sqlite3_value object passed as the
** first argument to a copy of the string or blob held in the aData[] 
** buffer. SQLITE_OK is returned if successful, or SQLITE_NOMEM if an OOM
** error occurs.
*/
static int sessionValueSetStr(
  sqlite3_value *pVal,            /* Set the value of this object */
  u8 *aData,                      /* Buffer containing string or blob data */
  int nData,                      /* Size of buffer aData[] in bytes */
  u8 enc                          /* String encoding (0 for blobs) */
){
  /* In theory this code could just pass SQLITE_TRANSIENT as the final
  ** argument to sqlite3ValueSetStr() and have the copy created 
  ** automatically. But doing so makes it difficult to detect any OOM
  ** error. Hence the code to create the copy externally. */
  u8 *aCopy = sqlite3_malloc(nData+1);
  if( aCopy==0 ) return SQLITE_NOMEM;
  memcpy(aCopy, aData, nData);
  sqlite3ValueSetStr(pVal, nData, (char*)aCopy, enc, sqlite3_free);
  return SQLITE_OK;
}

/*
** Deserialize a single record from a buffer in memory. See "RECORD FORMAT"
** for details.
**
** When this function is called, *paChange points to the start of the record
** to deserialize. Assuming no error occurs, *paChange is set to point to
** one byte after the end of the same record before this function returns.
** If the argument abPK is NULL, then the record contains nCol values. Or,
** if abPK is other than NULL, then the record contains only the PK fields
** (in other words, it is a patchset DELETE record).
**
** If successful, each element of the apOut[] array (allocated by the caller)
** is set to point to an sqlite3_value object containing the value read
** from the corresponding position in the record. If that value is not
** included in the record (i.e. because the record is part of an UPDATE change
** and the field was not modified), the corresponding element of apOut[] is
** set to NULL.
**
** It is the responsibility of the caller to free all sqlite_value structures
** using sqlite3_free().
**
** If an error occurs, an SQLite error code (e.g. SQLITE_NOMEM) is returned.
** The apOut[] array may have been partially populated in this case.
*/
static int sessionReadRecord(
  SessionInput *pIn,              /* Input data */
  int nCol,                       /* Number of values in record */
  u8 *abPK,                       /* Array of primary key flags, or NULL */
  sqlite3_value **apOut           /* Write values to this array */
){
  int i;                          /* Used to iterate through columns */
  int rc = SQLITE_OK;

  for(i=0; i<nCol && rc==SQLITE_OK; i++){
    int eType = 0;                /* Type of value (SQLITE_NULL, TEXT etc.) */
    if( abPK && abPK[i]==0 ) continue;
    rc = sessionInputBuffer(pIn, 9);
    if( rc==SQLITE_OK ){
      eType = pIn->aData[pIn->iNext++];
    }

    assert( apOut[i]==0 );
    if( eType ){
      apOut[i] = sqlite3ValueNew(0);
      if( !apOut[i] ) rc = SQLITE_NOMEM;
    }

    if( rc==SQLITE_OK ){
      u8 *aVal = &pIn->aData[pIn->iNext];
      if( eType==SQLITE_TEXT || eType==SQLITE_BLOB ){
        int nByte;
        pIn->iNext += sessionVarintGet(aVal, &nByte);
        rc = sessionInputBuffer(pIn, nByte);
        if( rc==SQLITE_OK ){
          u8 enc = (eType==SQLITE_TEXT ? SQLITE_UTF8 : 0);
          rc = sessionValueSetStr(apOut[i],&pIn->aData[pIn->iNext],nByte,enc);
        }
        pIn->iNext += nByte;
      }
      if( eType==SQLITE_INTEGER || eType==SQLITE_FLOAT ){
        sqlite3_int64 v = sessionGetI64(aVal);
        if( eType==SQLITE_INTEGER ){
          sqlite3VdbeMemSetInt64(apOut[i], v);
        }else{
          double d;
          memcpy(&d, &v, 8);
          sqlite3VdbeMemSetDouble(apOut[i], d);
        }
        pIn->iNext += 8;
      }
    }
  }

  return rc;
}

/*
** The input pointer currently points to the second byte of a table-header.
** Specifically, to the following:
**
**   + number of columns in table (varint)
**   + array of PK flags (1 byte per column),
**   + table name (nul terminated).
**
** This function ensures that all of the above is present in the input 
** buffer (i.e. that it can be accessed without any calls to xInput()).
** If successful, SQLITE_OK is returned. Otherwise, an SQLite error code.
** The input pointer is not moved.
*/
static int sessionChangesetBufferTblhdr(SessionInput *pIn, int *pnByte){
  int rc = SQLITE_OK;
  int nCol = 0;
  int nRead = 0;

  rc = sessionInputBuffer(pIn, 9);
  if( rc==SQLITE_OK ){
    nRead += sessionVarintGet(&pIn->aData[pIn->iNext + nRead], &nCol);
    rc = sessionInputBuffer(pIn, nRead+nCol+100);
    nRead += nCol;
  }

  while( rc==SQLITE_OK ){
    while( (pIn->iNext + nRead)<pIn->nData && pIn->aData[pIn->iNext + nRead] ){
      nRead++;
    }
    if( (pIn->iNext + nRead)<pIn->nData ) break;
    rc = sessionInputBuffer(pIn, nRead + 100);
  }
  *pnByte = nRead+1;
  return rc;
}

/*
** The input pointer currently points to the first byte of the first field
** of a record consisting of nCol columns. This function ensures the entire
** record is buffered. It does not move the input pointer.
**
** If successful, SQLITE_OK is returned and *pnByte is set to the size of
** the record in bytes. Otherwise, an SQLite error code is returned. The
** final value of *pnByte is undefined in this case.
*/
static int sessionChangesetBufferRecord(
  SessionInput *pIn,              /* Input data */
  int nCol,                       /* Number of columns in record */
  int *pnByte                     /* OUT: Size of record in bytes */
){
  int rc = SQLITE_OK;
  int nByte = 0;
  int i;
  for(i=0; rc==SQLITE_OK && i<nCol; i++){
    int eType;
    rc = sessionInputBuffer(pIn, nByte + 10);
    if( rc==SQLITE_OK ){
      eType = pIn->aData[pIn->iNext + nByte++];
      if( eType==SQLITE_TEXT || eType==SQLITE_BLOB ){
        int n;
        nByte += sessionVarintGet(&pIn->aData[pIn->iNext+nByte], &n);
        nByte += n;
        rc = sessionInputBuffer(pIn, nByte);
      }else if( eType==SQLITE_INTEGER || eType==SQLITE_FLOAT ){
        nByte += 8;
      }
    }
  }
  *pnByte = nByte;
  return rc;
}

/*
** The input pointer currently points to the second byte of a table-header.
** Specifically, to the following:
**
**   + number of columns in table (varint)
**   + array of PK flags (1 byte per column),
**   + table name (nul terminated).
**
** This function decodes the table-header and populates the p->nCol, 
** p->zTab and p->abPK[] variables accordingly. The p->apValue[] array is 
** also allocated or resized according to the new value of p->nCol. The
** input pointer is left pointing to the byte following the table header.
**
** If successful, SQLITE_OK is returned. Otherwise, an SQLite error code
** is returned and the final values of the various fields enumerated above
** are undefined.
*/
static int sessionChangesetReadTblhdr(sqlite3_changeset_iter *p){
  int rc;
  int nCopy;
  assert( p->rc==SQLITE_OK );

  rc = sessionChangesetBufferTblhdr(&p->in, &nCopy);
  if( rc==SQLITE_OK ){
    int nByte;
    int nVarint;
    nVarint = sessionVarintGet(&p->in.aData[p->in.iNext], &p->nCol);
    nCopy -= nVarint;
    p->in.iNext += nVarint;
    nByte = p->nCol * sizeof(sqlite3_value*) * 2 + nCopy;
    p->tblhdr.nBuf = 0;
    sessionBufferGrow(&p->tblhdr, nByte, &rc);
  }

  if( rc==SQLITE_OK ){
    int iPK = sizeof(sqlite3_value*)*p->nCol*2;
    memset(p->tblhdr.aBuf, 0, iPK);
    memcpy(&p->tblhdr.aBuf[iPK], &p->in.aData[p->in.iNext], nCopy);
    p->in.iNext += nCopy;
  }

  p->apValue = (sqlite3_value**)p->tblhdr.aBuf;
  p->abPK = (u8*)&p->apValue[p->nCol*2];
  p->zTab = (char*)&p->abPK[p->nCol];
  return (p->rc = rc);
}

/*
** Advance the changeset iterator to the next change.
**
** If both paRec and pnRec are NULL, then this function works like the public
** API sqlite3changeset_next(). If SQLITE_ROW is returned, then the
** sqlite3changeset_new() and old() APIs may be used to query for values.
**
** Otherwise, if paRec and pnRec are not NULL, then a pointer to the change
** record is written to *paRec before returning and the number of bytes in
** the record to *pnRec.
**
** Either way, this function returns SQLITE_ROW if the iterator is 
** successfully advanced to the next change in the changeset, an SQLite 
** error code if an error occurs, or SQLITE_DONE if there are no further 
** changes in the changeset.
*/
static int sessionChangesetNext(
  sqlite3_changeset_iter *p,      /* Changeset iterator */
  u8 **paRec,                     /* If non-NULL, store record pointer here */
  int *pnRec                      /* If non-NULL, store size of record here */
){
  int i;
  u8 op;

  assert( (paRec==0 && pnRec==0) || (paRec && pnRec) );

  /* If the iterator is in the error-state, return immediately. */
  if( p->rc!=SQLITE_OK ) return p->rc;

  /* Free the current contents of p->apValue[], if any. */
  if( p->apValue ){
    for(i=0; i<p->nCol*2; i++){
      sqlite3ValueFree(p->apValue[i]);
    }
    memset(p->apValue, 0, sizeof(sqlite3_value*)*p->nCol*2);
  }

  /* Make sure the buffer contains at least 10 bytes of input data, or all
  ** remaining data if there are less than 10 bytes available. This is
  ** sufficient either for the 'T' or 'P' byte and the varint that follows
  ** it, or for the two single byte values otherwise. */
  p->rc = sessionInputBuffer(&p->in, 2);
  if( p->rc!=SQLITE_OK ) return p->rc;

  /* If the iterator is already at the end of the changeset, return DONE. */
  if( p->in.iNext>=p->in.nData ){
    return SQLITE_DONE;
  }

  sessionDiscardData(&p->in);
  p->in.iCurrent = p->in.iNext;

  op = p->in.aData[p->in.iNext++];
  if( op=='T' || op=='P' ){
    p->bPatchset = (op=='P');
    if( sessionChangesetReadTblhdr(p) ) return p->rc;
    if( (p->rc = sessionInputBuffer(&p->in, 2)) ) return p->rc;
    p->in.iCurrent = p->in.iNext;
    op = p->in.aData[p->in.iNext++];
  }

  p->op = op;
  p->bIndirect = p->in.aData[p->in.iNext++];
  if( p->op!=SQLITE_UPDATE && p->op!=SQLITE_DELETE && p->op!=SQLITE_INSERT ){
    return (p->rc = SQLITE_CORRUPT_BKPT);
  }

  if( paRec ){ 
    int nVal;                     /* Number of values to buffer */
    if( p->bPatchset==0 && op==SQLITE_UPDATE ){
      nVal = p->nCol * 2;
    }else if( p->bPatchset && op==SQLITE_DELETE ){
      nVal = 0;
      for(i=0; i<p->nCol; i++) if( p->abPK[i] ) nVal++;
    }else{
      nVal = p->nCol;
    }
    p->rc = sessionChangesetBufferRecord(&p->in, nVal, pnRec);
    if( p->rc!=SQLITE_OK ) return p->rc;
    *paRec = &p->in.aData[p->in.iNext];
    p->in.iNext += *pnRec;
  }else{

    /* If this is an UPDATE or DELETE, read the old.* record. */
    if( p->op!=SQLITE_INSERT && (p->bPatchset==0 || p->op==SQLITE_DELETE) ){
      u8 *abPK = p->bPatchset ? p->abPK : 0;
      p->rc = sessionReadRecord(&p->in, p->nCol, abPK, p->apValue);
      if( p->rc!=SQLITE_OK ) return p->rc;
    }

    /* If this is an INSERT or UPDATE, read the new.* record. */
    if( p->op!=SQLITE_DELETE ){
      p->rc = sessionReadRecord(&p->in, p->nCol, 0, &p->apValue[p->nCol]);
      if( p->rc!=SQLITE_OK ) return p->rc;
    }

    if( p->bPatchset && p->op==SQLITE_UPDATE ){
      /* If this is an UPDATE that is part of a patchset, then all PK and
      ** modified fields are present in the new.* record. The old.* record
      ** is currently completely empty. This block shifts the PK fields from
      ** new.* to old.*, to accommodate the code that reads these arrays.  */
      int i;
      for(i=0; i<p->nCol; i++){
        assert( p->apValue[i]==0 );
        assert( p->abPK[i]==0 || p->apValue[i+p->nCol] );
        if( p->abPK[i] ){
          p->apValue[i] = p->apValue[i+p->nCol];
          p->apValue[i+p->nCol] = 0;
        }
      }
    }
  }

  return SQLITE_ROW;
}

/*
** Advance an iterator created by sqlite3changeset_start() to the next
** change in the changeset. This function may return SQLITE_ROW, SQLITE_DONE
** or SQLITE_CORRUPT.
**
** This function may not be called on iterators passed to a conflict handler
** callback by changeset_apply().
*/
SQLITE_API int SQLITE_STDCALL sqlite3changeset_next(sqlite3_changeset_iter *p){
  return sessionChangesetNext(p, 0, 0);
}

/*
** The following function extracts information on the current change
** from a changeset iterator. It may only be called after changeset_next()
** has returned SQLITE_ROW.
*/
SQLITE_API int SQLITE_STDCALL sqlite3changeset_op(
  sqlite3_changeset_iter *pIter,  /* Iterator handle */
  const char **pzTab,             /* OUT: Pointer to table name */
  int *pnCol,                     /* OUT: Number of columns in table */
  int *pOp,                       /* OUT: SQLITE_INSERT, DELETE or UPDATE */
  int *pbIndirect                 /* OUT: True if change is indirect */
){
  *pOp = pIter->op;
  *pnCol = pIter->nCol;
  *pzTab = pIter->zTab;
  if( pbIndirect ) *pbIndirect = pIter->bIndirect;
  return SQLITE_OK;
}

/*
** Return information regarding the PRIMARY KEY and number of columns in
** the database table affected by the change that pIter currently points
** to. This function may only be called after changeset_next() returns
** SQLITE_ROW.
*/
SQLITE_API int SQLITE_STDCALL sqlite3changeset_pk(
  sqlite3_changeset_iter *pIter,  /* Iterator object */
  unsigned char **pabPK,          /* OUT: Array of boolean - true for PK cols */
  int *pnCol                      /* OUT: Number of entries in output array */
){
  *pabPK = pIter->abPK;
  if( pnCol ) *pnCol = pIter->nCol;
  return SQLITE_OK;
}

/*
** This function may only be called while the iterator is pointing to an
** SQLITE_UPDATE or SQLITE_DELETE change (see sqlite3changeset_op()).
** Otherwise, SQLITE_MISUSE is returned.
**
** It sets *ppValue to point to an sqlite3_value structure containing the
** iVal'th value in the old.* record. Or, if that particular value is not
** included in the record (because the change is an UPDATE and the field
** was not modified and is not a PK column), set *ppValue to NULL.
**
** If value iVal is out-of-range, SQLITE_RANGE is returned and *ppValue is
** not modified. Otherwise, SQLITE_OK.
*/
SQLITE_API int SQLITE_STDCALL sqlite3changeset_old(
  sqlite3_changeset_iter *pIter,  /* Changeset iterator */
  int iVal,                       /* Index of old.* value to retrieve */
  sqlite3_value **ppValue         /* OUT: Old value (or NULL pointer) */
){
  if( pIter->op!=SQLITE_UPDATE && pIter->op!=SQLITE_DELETE ){
    return SQLITE_MISUSE;
  }
  if( iVal<0 || iVal>=pIter->nCol ){
    return SQLITE_RANGE;
  }
  *ppValue = pIter->apValue[iVal];
  return SQLITE_OK;
}

/*
** This function may only be called while the iterator is pointing to an
** SQLITE_UPDATE or SQLITE_INSERT change (see sqlite3changeset_op()).
** Otherwise, SQLITE_MISUSE is returned.
**
** It sets *ppValue to point to an sqlite3_value structure containing the
** iVal'th value in the new.* record. Or, if that particular value is not
** included in the record (because the change is an UPDATE and the field
** was not modified), set *ppValue to NULL.
**
** If value iVal is out-of-range, SQLITE_RANGE is returned and *ppValue is
** not modified. Otherwise, SQLITE_OK.
*/
SQLITE_API int SQLITE_STDCALL sqlite3changeset_new(
  sqlite3_changeset_iter *pIter,  /* Changeset iterator */
  int iVal,                       /* Index of new.* value to retrieve */
  sqlite3_value **ppValue         /* OUT: New value (or NULL pointer) */
){
  if( pIter->op!=SQLITE_UPDATE && pIter->op!=SQLITE_INSERT ){
    return SQLITE_MISUSE;
  }
  if( iVal<0 || iVal>=pIter->nCol ){
    return SQLITE_RANGE;
  }
  *ppValue = pIter->apValue[pIter->nCol+iVal];
  return SQLITE_OK;
}

/*
** The following two macros are used internally. They are similar to the
** sqlite3changeset_new() and sqlite3changeset_old() functions, except that
** they omit all error checking and return a pointer to the requested value.
*/
#define sessionChangesetNew(pIter, iVal) (pIter)->apValue[(pIter)->nCol+(iVal)]
#define sessionChangesetOld(pIter, iVal) (pIter)->apValue[(iVal)]

/*
** This function may only be called with a changeset iterator that has been
** passed to an SQLITE_CHANGESET_DATA or SQLITE_CHANGESET_CONFLICT 
** conflict-handler function. Otherwise, SQLITE_MISUSE is returned.
**
** If successful, *ppValue is set to point to an sqlite3_value structure
** containing the iVal'th value of the conflicting record.
**
** If value iVal is out-of-range or some other error occurs, an SQLite error
** code is returned. Otherwise, SQLITE_OK.
*/
SQLITE_API int SQLITE_STDCALL sqlite3changeset_conflict(
  sqlite3_changeset_iter *pIter,  /* Changeset iterator */
  int iVal,                       /* Index of conflict record value to fetch */
  sqlite3_value **ppValue         /* OUT: Value from conflicting row */
){
  if( !pIter->pConflict ){
    return SQLITE_MISUSE;
  }
  if( iVal<0 || iVal>=sqlite3_column_count(pIter->pConflict) ){
    return SQLITE_RANGE;
  }
  *ppValue = sqlite3_column_value(pIter->pConflict, iVal);
  return SQLITE_OK;
}

/*
** This function may only be called with an iterator passed to an
** SQLITE_CHANGESET_FOREIGN_KEY conflict handler callback. In this case
** it sets the output variable to the total number of known foreign key
** violations in the destination database and returns SQLITE_OK.
**
** In all other cases this function returns SQLITE_MISUSE.
*/
SQLITE_API int SQLITE_STDCALL sqlite3changeset_fk_conflicts(
  sqlite3_changeset_iter *pIter,  /* Changeset iterator */
  int *pnOut                      /* OUT: Number of FK violations */
){
  if( pIter->pConflict || pIter->apValue ){
    return SQLITE_MISUSE;
  }
  *pnOut = pIter->nCol;
  return SQLITE_OK;
}


/*
** Finalize an iterator allocated with sqlite3changeset_start().
**
** This function may not be called on iterators passed to a conflict handler
** callback by changeset_apply().
*/
SQLITE_API int SQLITE_STDCALL sqlite3changeset_finalize(sqlite3_changeset_iter *p){
  int rc = SQLITE_OK;
  if( p ){
    int i;                        /* Used to iterate through p->apValue[] */
    rc = p->rc;
    if( p->apValue ){
      for(i=0; i<p->nCol*2; i++) sqlite3ValueFree(p->apValue[i]);
    }
    sqlite3_free(p->tblhdr.aBuf);
    sqlite3_free(p->in.buf.aBuf);
    sqlite3_free(p);
  }
  return rc;
}

static int sessionChangesetInvert(
  SessionInput *pInput,           /* Input changeset */
  int (*xOutput)(void *pOut, const void *pData, int nData),
  void *pOut,
  int *pnInverted,                /* OUT: Number of bytes in output changeset */
  void **ppInverted               /* OUT: Inverse of pChangeset */
){
  int rc = SQLITE_OK;             /* Return value */
  SessionBuffer sOut;             /* Output buffer */
  int nCol = 0;                   /* Number of cols in current table */
  u8 *abPK = 0;                   /* PK array for current table */
  sqlite3_value **apVal = 0;      /* Space for values for UPDATE inversion */
  SessionBuffer sPK = {0, 0, 0};  /* PK array for current table */

  /* Initialize the output buffer */
  memset(&sOut, 0, sizeof(SessionBuffer));

  /* Zero the output variables in case an error occurs. */
  if( ppInverted ){
    *ppInverted = 0;
    *pnInverted = 0;
  }

  while( 1 ){
    u8 eType;

    /* Test for EOF. */
    if( (rc = sessionInputBuffer(pInput, 2)) ) goto finished_invert;
    if( pInput->iNext>=pInput->nData ) break;
    eType = pInput->aData[pInput->iNext];

    switch( eType ){
      case 'T': {
        /* A 'table' record consists of:
        **
        **   * A constant 'T' character,
        **   * Number of columns in said table (a varint),
        **   * An array of nCol bytes (sPK),
        **   * A nul-terminated table name.
        */
        int nByte;
        int nVar;
        pInput->iNext++;
        if( (rc = sessionChangesetBufferTblhdr(pInput, &nByte)) ){
          goto finished_invert;
        }
        nVar = sessionVarintGet(&pInput->aData[pInput->iNext], &nCol);
        sPK.nBuf = 0;
        sessionAppendBlob(&sPK, &pInput->aData[pInput->iNext+nVar], nCol, &rc);
        sessionAppendByte(&sOut, eType, &rc);
        sessionAppendBlob(&sOut, &pInput->aData[pInput->iNext], nByte, &rc);
        if( rc ) goto finished_invert;

        pInput->iNext += nByte;
        sqlite3_free(apVal);
        apVal = 0;
        abPK = sPK.aBuf;
        break;
      }

      case SQLITE_INSERT:
      case SQLITE_DELETE: {
        int nByte;
        int bIndirect = pInput->aData[pInput->iNext+1];
        int eType2 = (eType==SQLITE_DELETE ? SQLITE_INSERT : SQLITE_DELETE);
        pInput->iNext += 2;
        assert( rc==SQLITE_OK );
        rc = sessionChangesetBufferRecord(pInput, nCol, &nByte);
        sessionAppendByte(&sOut, eType2, &rc);
        sessionAppendByte(&sOut, bIndirect, &rc);
        sessionAppendBlob(&sOut, &pInput->aData[pInput->iNext], nByte, &rc);
        pInput->iNext += nByte;
        if( rc ) goto finished_invert;
        break;
      }

      case SQLITE_UPDATE: {
        int iCol;

        if( 0==apVal ){
          apVal = (sqlite3_value **)sqlite3_malloc(sizeof(apVal[0])*nCol*2);
          if( 0==apVal ){
            rc = SQLITE_NOMEM;
            goto finished_invert;
          }
          memset(apVal, 0, sizeof(apVal[0])*nCol*2);
        }

        /* Write the header for the new UPDATE change. Same as the original. */
        sessionAppendByte(&sOut, eType, &rc);
        sessionAppendByte(&sOut, pInput->aData[pInput->iNext+1], &rc);

        /* Read the old.* and new.* records for the update change. */
        pInput->iNext += 2;
        rc = sessionReadRecord(pInput, nCol, 0, &apVal[0]);
        if( rc==SQLITE_OK ){
          rc = sessionReadRecord(pInput, nCol, 0, &apVal[nCol]);
        }

        /* Write the new old.* record. Consists of the PK columns from the
        ** original old.* record, and the other values from the original
        ** new.* record. */
        for(iCol=0; iCol<nCol; iCol++){
          sqlite3_value *pVal = apVal[iCol + (abPK[iCol] ? 0 : nCol)];
          sessionAppendValue(&sOut, pVal, &rc);
        }

        /* Write the new new.* record. Consists of a copy of all values
        ** from the original old.* record, except for the PK columns, which
        ** are set to "undefined". */
        for(iCol=0; iCol<nCol; iCol++){
          sqlite3_value *pVal = (abPK[iCol] ? 0 : apVal[iCol]);
          sessionAppendValue(&sOut, pVal, &rc);
        }

        for(iCol=0; iCol<nCol*2; iCol++){
          sqlite3ValueFree(apVal[iCol]);
        }
        memset(apVal, 0, sizeof(apVal[0])*nCol*2);
        if( rc!=SQLITE_OK ){
          goto finished_invert;
        }

        break;
      }

      default:
        rc = SQLITE_CORRUPT_BKPT;
        goto finished_invert;
    }

    assert( rc==SQLITE_OK );
    if( xOutput && sOut.nBuf>=SESSIONS_STRM_CHUNK_SIZE ){
      rc = xOutput(pOut, sOut.aBuf, sOut.nBuf);
      sOut.nBuf = 0;
      if( rc!=SQLITE_OK ) goto finished_invert;
    }
  }

  assert( rc==SQLITE_OK );
  if( pnInverted ){
    *pnInverted = sOut.nBuf;
    *ppInverted = sOut.aBuf;
    sOut.aBuf = 0;
  }else if( sOut.nBuf>0 ){
    rc = xOutput(pOut, sOut.aBuf, sOut.nBuf);
  }

 finished_invert:
  sqlite3_free(sOut.aBuf);
  sqlite3_free(apVal);
  sqlite3_free(sPK.aBuf);
  return rc;
}


/*
** Invert a changeset object.
*/
SQLITE_API int SQLITE_STDCALL sqlite3changeset_invert(
  int nChangeset,                 /* Number of bytes in input */
  const void *pChangeset,         /* Input changeset */
  int *pnInverted,                /* OUT: Number of bytes in output changeset */
  void **ppInverted               /* OUT: Inverse of pChangeset */
){
  SessionInput sInput;

  /* Set up the input stream */
  memset(&sInput, 0, sizeof(SessionInput));
  sInput.nData = nChangeset;
  sInput.aData = (u8*)pChangeset;

  return sessionChangesetInvert(&sInput, 0, 0, pnInverted, ppInverted);
}

/*
** Streaming version of sqlite3changeset_invert().
*/
SQLITE_API int SQLITE_STDCALL sqlite3changeset_invert_strm(
  int (*xInput)(void *pIn, void *pData, int *pnData),
  void *pIn,
  int (*xOutput)(void *pOut, const void *pData, int nData),
  void *pOut
){
  SessionInput sInput;
  int rc;

  /* Set up the input stream */
  memset(&sInput, 0, sizeof(SessionInput));
  sInput.xInput = xInput;
  sInput.pIn = pIn;

  rc = sessionChangesetInvert(&sInput, xOutput, pOut, 0, 0);
  sqlite3_free(sInput.buf.aBuf);
  return rc;
}

typedef struct SessionApplyCtx SessionApplyCtx;
struct SessionApplyCtx {
  sqlite3 *db;
  sqlite3_stmt *pDelete;          /* DELETE statement */
  sqlite3_stmt *pUpdate;          /* UPDATE statement */
  sqlite3_stmt *pInsert;          /* INSERT statement */
  sqlite3_stmt *pSelect;          /* SELECT statement */
  int nCol;                       /* Size of azCol[] and abPK[] arrays */
  const char **azCol;             /* Array of column names */
  u8 *abPK;                       /* Boolean array - true if column is in PK */

  int bDeferConstraints;          /* True to defer constraints */
  SessionBuffer constraints;      /* Deferred constraints are stored here */
};

/*
** Formulate a statement to DELETE a row from database db. Assuming a table
** structure like this:
**
**     CREATE TABLE x(a, b, c, d, PRIMARY KEY(a, c));
**
** The DELETE statement looks like this:
**
**     DELETE FROM x WHERE a = :1 AND c = :3 AND (:5 OR b IS :2 AND d IS :4)
**
** Variable :5 (nCol+1) is a boolean. It should be set to 0 if we require
** matching b and d values, or 1 otherwise. The second case comes up if the
** conflict handler is invoked with NOTFOUND and returns CHANGESET_REPLACE.
**
** If successful, SQLITE_OK is returned and SessionApplyCtx.pDelete is left
** pointing to the prepared version of the SQL statement.
*/
static int sessionDeleteRow(
  sqlite3 *db,                    /* Database handle */
  const char *zTab,               /* Table name */
  SessionApplyCtx *p              /* Session changeset-apply context */
){
  int i;
  const char *zSep = "";
  int rc = SQLITE_OK;
  SessionBuffer buf = {0, 0, 0};
  int nPk = 0;

  sessionAppendStr(&buf, "DELETE FROM ", &rc);
  sessionAppendIdent(&buf, zTab, &rc);
  sessionAppendStr(&buf, " WHERE ", &rc);

  for(i=0; i<p->nCol; i++){
    if( p->abPK[i] ){
      nPk++;
      sessionAppendStr(&buf, zSep, &rc);
      sessionAppendIdent(&buf, p->azCol[i], &rc);
      sessionAppendStr(&buf, " = ?", &rc);
      sessionAppendInteger(&buf, i+1, &rc);
      zSep = " AND ";
    }
  }

  if( nPk<p->nCol ){
    sessionAppendStr(&buf, " AND (?", &rc);
    sessionAppendInteger(&buf, p->nCol+1, &rc);
    sessionAppendStr(&buf, " OR ", &rc);

    zSep = "";
    for(i=0; i<p->nCol; i++){
      if( !p->abPK[i] ){
        sessionAppendStr(&buf, zSep, &rc);
        sessionAppendIdent(&buf, p->azCol[i], &rc);
        sessionAppendStr(&buf, " IS ?", &rc);
        sessionAppendInteger(&buf, i+1, &rc);
        zSep = "AND ";
      }
    }
    sessionAppendStr(&buf, ")", &rc);
  }

  if( rc==SQLITE_OK ){
    rc = sqlite3_prepare_v2(db, (char *)buf.aBuf, buf.nBuf, &p->pDelete, 0);
  }
  sqlite3_free(buf.aBuf);

  return rc;
}

/*
** Formulate and prepare a statement to UPDATE a row from database db. 
** Assuming a table structure like this:
**
**     CREATE TABLE x(a, b, c, d, PRIMARY KEY(a, c));
**
** The UPDATE statement looks like this:
**
**     UPDATE x SET
**     a = CASE WHEN ?2  THEN ?3  ELSE a END,
**     b = CASE WHEN ?5  THEN ?6  ELSE b END,
**     c = CASE WHEN ?8  THEN ?9  ELSE c END,
**     d = CASE WHEN ?11 THEN ?12 ELSE d END
**     WHERE a = ?1 AND c = ?7 AND (?13 OR 
**       (?5==0 OR b IS ?4) AND (?11==0 OR d IS ?10) AND
**     )
**
** For each column in the table, there are three variables to bind:
**
**     ?(i*3+1)    The old.* value of the column, if any.
**     ?(i*3+2)    A boolean flag indicating that the value is being modified.
**     ?(i*3+3)    The new.* value of the column, if any.
**
** Also, a boolean flag that, if set to true, causes the statement to update
** a row even if the non-PK values do not match. This is required if the
** conflict-handler is invoked with CHANGESET_DATA and returns
** CHANGESET_REPLACE. This is variable "?(nCol*3+1)".
**
** If successful, SQLITE_OK is returned and SessionApplyCtx.pUpdate is left
** pointing to the prepared version of the SQL statement.
*/
static int sessionUpdateRow(
  sqlite3 *db,                    /* Database handle */
  const char *zTab,               /* Table name */
  SessionApplyCtx *p              /* Session changeset-apply context */
){
  int rc = SQLITE_OK;
  int i;
  const char *zSep = "";
  SessionBuffer buf = {0, 0, 0};

  /* Append "UPDATE tbl SET " */
  sessionAppendStr(&buf, "UPDATE ", &rc);
  sessionAppendIdent(&buf, zTab, &rc);
  sessionAppendStr(&buf, " SET ", &rc);

  /* Append the assignments */
  for(i=0; i<p->nCol; i++){
    sessionAppendStr(&buf, zSep, &rc);
    sessionAppendIdent(&buf, p->azCol[i], &rc);
    sessionAppendStr(&buf, " = CASE WHEN ?", &rc);
    sessionAppendInteger(&buf, i*3+2, &rc);
    sessionAppendStr(&buf, " THEN ?", &rc);
    sessionAppendInteger(&buf, i*3+3, &rc);
    sessionAppendStr(&buf, " ELSE ", &rc);
    sessionAppendIdent(&buf, p->azCol[i], &rc);
    sessionAppendStr(&buf, " END", &rc);
    zSep = ", ";
  }

  /* Append the PK part of the WHERE clause */
  sessionAppendStr(&buf, " WHERE ", &rc);
  for(i=0; i<p->nCol; i++){
    if( p->abPK[i] ){
      sessionAppendIdent(&buf, p->azCol[i], &rc);
      sessionAppendStr(&buf, " = ?", &rc);
      sessionAppendInteger(&buf, i*3+1, &rc);
      sessionAppendStr(&buf, " AND ", &rc);
    }
  }

  /* Append the non-PK part of the WHERE clause */
  sessionAppendStr(&buf, " (?", &rc);
  sessionAppendInteger(&buf, p->nCol*3+1, &rc);
  sessionAppendStr(&buf, " OR 1", &rc);
  for(i=0; i<p->nCol; i++){
    if( !p->abPK[i] ){
      sessionAppendStr(&buf, " AND (?", &rc);
      sessionAppendInteger(&buf, i*3+2, &rc);
      sessionAppendStr(&buf, "=0 OR ", &rc);
      sessionAppendIdent(&buf, p->azCol[i], &rc);
      sessionAppendStr(&buf, " IS ?", &rc);
      sessionAppendInteger(&buf, i*3+1, &rc);
      sessionAppendStr(&buf, ")", &rc);
    }
  }
  sessionAppendStr(&buf, ")", &rc);

  if( rc==SQLITE_OK ){
    rc = sqlite3_prepare_v2(db, (char *)buf.aBuf, buf.nBuf, &p->pUpdate, 0);
  }
  sqlite3_free(buf.aBuf);

  return rc;
}

/*
** Formulate and prepare an SQL statement to query table zTab by primary
** key. Assuming the following table structure:
**
**     CREATE TABLE x(a, b, c, d, PRIMARY KEY(a, c));
**
** The SELECT statement looks like this:
**
**     SELECT * FROM x WHERE a = ?1 AND c = ?3
**
** If successful, SQLITE_OK is returned and SessionApplyCtx.pSelect is left
** pointing to the prepared version of the SQL statement.
*/
static int sessionSelectRow(
  sqlite3 *db,                    /* Database handle */
  const char *zTab,               /* Table name */
  SessionApplyCtx *p              /* Session changeset-apply context */
){
  return sessionSelectStmt(
      db, "main", zTab, p->nCol, p->azCol, p->abPK, &p->pSelect);
}

/*
** Formulate and prepare an INSERT statement to add a record to table zTab.
** For example:
**
**     INSERT INTO main."zTab" VALUES(?1, ?2, ?3 ...);
**
** If successful, SQLITE_OK is returned and SessionApplyCtx.pInsert is left
** pointing to the prepared version of the SQL statement.
*/
static int sessionInsertRow(
  sqlite3 *db,                    /* Database handle */
  const char *zTab,               /* Table name */
  SessionApplyCtx *p              /* Session changeset-apply context */
){
  int rc = SQLITE_OK;
  int i;
  SessionBuffer buf = {0, 0, 0};

  sessionAppendStr(&buf, "INSERT INTO main.", &rc);
  sessionAppendIdent(&buf, zTab, &rc);
  sessionAppendStr(&buf, " VALUES(?", &rc);
  for(i=1; i<p->nCol; i++){
    sessionAppendStr(&buf, ", ?", &rc);
  }
  sessionAppendStr(&buf, ")", &rc);

  if( rc==SQLITE_OK ){
    rc = sqlite3_prepare_v2(db, (char *)buf.aBuf, buf.nBuf, &p->pInsert, 0);
  }
  sqlite3_free(buf.aBuf);
  return rc;
}

/*
** A wrapper around sqlite3_bind_value() that detects an extra problem. 
** See comments in the body of this function for details.
*/
static int sessionBindValue(
  sqlite3_stmt *pStmt,            /* Statement to bind value to */
  int i,                          /* Parameter number to bind to */
  sqlite3_value *pVal             /* Value to bind */
){
  int eType = sqlite3_value_type(pVal);
  /* COVERAGE: The (pVal->z==0) branch is never true using current versions
  ** of SQLite. If a malloc fails in an sqlite3_value_xxx() function, either
  ** the (pVal->z) variable remains as it was or the type of the value is
  ** set to SQLITE_NULL.  */
  if( (eType==SQLITE_TEXT || eType==SQLITE_BLOB) && pVal->z==0 ){
    /* This condition occurs when an earlier OOM in a call to
    ** sqlite3_value_text() or sqlite3_value_blob() (perhaps from within
    ** a conflict-handler) has zeroed the pVal->z pointer. Return NOMEM. */
    return SQLITE_NOMEM;
  }
  return sqlite3_bind_value(pStmt, i, pVal);
}

/*
** Iterator pIter must point to an SQLITE_INSERT entry. This function 
** transfers new.* values from the current iterator entry to statement
** pStmt. The table being inserted into has nCol columns.
**
** New.* value $i from the iterator is bound to variable ($i+1) of 
** statement pStmt. If parameter abPK is NULL, all values from 0 to (nCol-1)
** are transfered to the statement. Otherwise, if abPK is not NULL, it points
** to an array nCol elements in size. In this case only those values for 
** which abPK[$i] is true are read from the iterator and bound to the 
** statement.
**
** An SQLite error code is returned if an error occurs. Otherwise, SQLITE_OK.
*/
static int sessionBindRow(
  sqlite3_changeset_iter *pIter,  /* Iterator to read values from */
  int(*xValue)(sqlite3_changeset_iter *, int, sqlite3_value **),
  int nCol,                       /* Number of columns */
  u8 *abPK,                       /* If not NULL, bind only if true */
  sqlite3_stmt *pStmt             /* Bind values to this statement */
){
  int i;
  int rc = SQLITE_OK;

  /* Neither sqlite3changeset_old or sqlite3changeset_new can fail if the
  ** argument iterator points to a suitable entry. Make sure that xValue 
  ** is one of these to guarantee that it is safe to ignore the return 
  ** in the code below. */
  assert( xValue==sqlite3changeset_old || xValue==sqlite3changeset_new );

  for(i=0; rc==SQLITE_OK && i<nCol; i++){
    if( !abPK || abPK[i] ){
      sqlite3_value *pVal;
      (void)xValue(pIter, i, &pVal);
      rc = sessionBindValue(pStmt, i+1, pVal);
    }
  }
  return rc;
}

/*
** SQL statement pSelect is as generated by the sessionSelectRow() function.
** This function binds the primary key values from the change that changeset
** iterator pIter points to to the SELECT and attempts to seek to the table
** entry. If a row is found, the SELECT statement left pointing at the row 
** and SQLITE_ROW is returned. Otherwise, if no row is found and no error
** has occured, the statement is reset and SQLITE_OK is returned. If an
** error occurs, the statement is reset and an SQLite error code is returned.
**
** If this function returns SQLITE_ROW, the caller must eventually reset() 
** statement pSelect. If any other value is returned, the statement does
** not require a reset().
**
** If the iterator currently points to an INSERT record, bind values from the
** new.* record to the SELECT statement. Or, if it points to a DELETE or
** UPDATE, bind values from the old.* record. 
*/
static int sessionSeekToRow(
  sqlite3 *db,                    /* Database handle */
  sqlite3_changeset_iter *pIter,  /* Changeset iterator */
  u8 *abPK,                       /* Primary key flags array */
  sqlite3_stmt *pSelect           /* SELECT statement from sessionSelectRow() */
){
  int rc;                         /* Return code */
  int nCol;                       /* Number of columns in table */
  int op;                         /* Changset operation (SQLITE_UPDATE etc.) */
  const char *zDummy;             /* Unused */

  sqlite3changeset_op(pIter, &zDummy, &nCol, &op, 0);
  rc = sessionBindRow(pIter, 
      op==SQLITE_INSERT ? sqlite3changeset_new : sqlite3changeset_old,
      nCol, abPK, pSelect
  );

  if( rc==SQLITE_OK ){
    rc = sqlite3_step(pSelect);
    if( rc!=SQLITE_ROW ) rc = sqlite3_reset(pSelect);
  }

  return rc;
}

/*
** Invoke the conflict handler for the change that the changeset iterator
** currently points to.
**
** Argument eType must be either CHANGESET_DATA or CHANGESET_CONFLICT.
** If argument pbReplace is NULL, then the type of conflict handler invoked
** depends solely on eType, as follows:
**
**    eType value                 Value passed to xConflict
**    -------------------------------------------------
**    CHANGESET_DATA              CHANGESET_NOTFOUND
**    CHANGESET_CONFLICT          CHANGESET_CONSTRAINT
**
** Or, if pbReplace is not NULL, then an attempt is made to find an existing
** record with the same primary key as the record about to be deleted, updated
** or inserted. If such a record can be found, it is available to the conflict
** handler as the "conflicting" record. In this case the type of conflict
** handler invoked is as follows:
**
**    eType value         PK Record found?   Value passed to xConflict
**    ----------------------------------------------------------------
**    CHANGESET_DATA      Yes                CHANGESET_DATA
**    CHANGESET_DATA      No                 CHANGESET_NOTFOUND
**    CHANGESET_CONFLICT  Yes                CHANGESET_CONFLICT
**    CHANGESET_CONFLICT  No                 CHANGESET_CONSTRAINT
**
** If pbReplace is not NULL, and a record with a matching PK is found, and
** the conflict handler function returns SQLITE_CHANGESET_REPLACE, *pbReplace
** is set to non-zero before returning SQLITE_OK.
**
** If the conflict handler returns SQLITE_CHANGESET_ABORT, SQLITE_ABORT is
** returned. Or, if the conflict handler returns an invalid value, 
** SQLITE_MISUSE. If the conflict handler returns SQLITE_CHANGESET_OMIT,
** this function returns SQLITE_OK.
*/
static int sessionConflictHandler(
  int eType,                      /* Either CHANGESET_DATA or CONFLICT */
  SessionApplyCtx *p,             /* changeset_apply() context */
  sqlite3_changeset_iter *pIter,  /* Changeset iterator */
  int(*xConflict)(void *, int, sqlite3_changeset_iter*),
  void *pCtx,                     /* First argument for conflict handler */
  int *pbReplace                  /* OUT: Set to true if PK row is found */
){
  int res;                        /* Value returned by conflict handler */
  int rc;
  int nCol;
  int op;
  const char *zDummy;

  sqlite3changeset_op(pIter, &zDummy, &nCol, &op, 0);

  assert( eType==SQLITE_CHANGESET_CONFLICT || eType==SQLITE_CHANGESET_DATA );
  assert( SQLITE_CHANGESET_CONFLICT+1==SQLITE_CHANGESET_CONSTRAINT );
  assert( SQLITE_CHANGESET_DATA+1==SQLITE_CHANGESET_NOTFOUND );

  /* Bind the new.* PRIMARY KEY values to the SELECT statement. */
  if( pbReplace ){
    rc = sessionSeekToRow(p->db, pIter, p->abPK, p->pSelect);
  }else{
    rc = SQLITE_OK;
  }

  if( rc==SQLITE_ROW ){
    /* There exists another row with the new.* primary key. */
    pIter->pConflict = p->pSelect;
    res = xConflict(pCtx, eType, pIter);
    pIter->pConflict = 0;
    rc = sqlite3_reset(p->pSelect);
  }else if( rc==SQLITE_OK ){
    if( p->bDeferConstraints && eType==SQLITE_CHANGESET_CONFLICT ){
      /* Instead of invoking the conflict handler, append the change blob
      ** to the SessionApplyCtx.constraints buffer. */
      u8 *aBlob = &pIter->in.aData[pIter->in.iCurrent];
      int nBlob = pIter->in.iNext - pIter->in.iCurrent;
      sessionAppendBlob(&p->constraints, aBlob, nBlob, &rc);
      res = SQLITE_CHANGESET_OMIT;
    }else{
      /* No other row with the new.* primary key. */
      res = xConflict(pCtx, eType+1, pIter);
      if( res==SQLITE_CHANGESET_REPLACE ) rc = SQLITE_MISUSE;
    }
  }

  if( rc==SQLITE_OK ){
    switch( res ){
      case SQLITE_CHANGESET_REPLACE:
        assert( pbReplace );
        *pbReplace = 1;
        break;

      case SQLITE_CHANGESET_OMIT:
        break;

      case SQLITE_CHANGESET_ABORT:
        rc = SQLITE_ABORT;
        break;

      default:
        rc = SQLITE_MISUSE;
        break;
    }
  }

  return rc;
}

/*
** Attempt to apply the change that the iterator passed as the first argument
** currently points to to the database. If a conflict is encountered, invoke
** the conflict handler callback.
**
** If argument pbRetry is NULL, then ignore any CHANGESET_DATA conflict. If
** one is encountered, update or delete the row with the matching primary key
** instead. Or, if pbRetry is not NULL and a CHANGESET_DATA conflict occurs,
** invoke the conflict handler. If it returns CHANGESET_REPLACE, set *pbRetry
** to true before returning. In this case the caller will invoke this function
** again, this time with pbRetry set to NULL.
**
** If argument pbReplace is NULL and a CHANGESET_CONFLICT conflict is 
** encountered invoke the conflict handler with CHANGESET_CONSTRAINT instead.
** Or, if pbReplace is not NULL, invoke it with CHANGESET_CONFLICT. If such
** an invocation returns SQLITE_CHANGESET_REPLACE, set *pbReplace to true
** before retrying. In this case the caller attempts to remove the conflicting
** row before invoking this function again, this time with pbReplace set 
** to NULL.
**
** If any conflict handler returns SQLITE_CHANGESET_ABORT, this function
** returns SQLITE_ABORT. Otherwise, if no error occurs, SQLITE_OK is 
** returned.
*/
static int sessionApplyOneOp(
  sqlite3_changeset_iter *pIter,  /* Changeset iterator */
  SessionApplyCtx *p,             /* changeset_apply() context */
  int(*xConflict)(void *, int, sqlite3_changeset_iter *),
  void *pCtx,                     /* First argument for the conflict handler */
  int *pbReplace,                 /* OUT: True to remove PK row and retry */
  int *pbRetry                    /* OUT: True to retry. */
){
  const char *zDummy;
  int op;
  int nCol;
  int rc = SQLITE_OK;

  assert( p->pDelete && p->pUpdate && p->pInsert && p->pSelect );
  assert( p->azCol && p->abPK );
  assert( !pbReplace || *pbReplace==0 );

  sqlite3changeset_op(pIter, &zDummy, &nCol, &op, 0);

  if( op==SQLITE_DELETE ){

    /* Bind values to the DELETE statement. If conflict handling is required,
    ** bind values for all columns and set bound variable (nCol+1) to true.
    ** Or, if conflict handling is not required, bind just the PK column
    ** values and, if it exists, set (nCol+1) to false. Conflict handling
    ** is not required if:
    **
    **   * this is a patchset, or
    **   * (pbRetry==0), or
    **   * all columns of the table are PK columns (in this case there is
    **     no (nCol+1) variable to bind to).
    */
    u8 *abPK = (pIter->bPatchset ? p->abPK : 0);
    rc = sessionBindRow(pIter, sqlite3changeset_old, nCol, abPK, p->pDelete);
    if( rc==SQLITE_OK && sqlite3_bind_parameter_count(p->pDelete)>nCol ){
      rc = sqlite3_bind_int(p->pDelete, nCol+1, (pbRetry==0 || abPK));
    }
    if( rc!=SQLITE_OK ) return rc;

    sqlite3_step(p->pDelete);
    rc = sqlite3_reset(p->pDelete);
    if( rc==SQLITE_OK && sqlite3_changes(p->db)==0 ){
      rc = sessionConflictHandler(
          SQLITE_CHANGESET_DATA, p, pIter, xConflict, pCtx, pbRetry
      );
    }else if( (rc&0xff)==SQLITE_CONSTRAINT ){
      rc = sessionConflictHandler(
          SQLITE_CHANGESET_CONFLICT, p, pIter, xConflict, pCtx, 0
      );
    }

  }else if( op==SQLITE_UPDATE ){
    int i;

    /* Bind values to the UPDATE statement. */
    for(i=0; rc==SQLITE_OK && i<nCol; i++){
      sqlite3_value *pOld = sessionChangesetOld(pIter, i);
      sqlite3_value *pNew = sessionChangesetNew(pIter, i);

      sqlite3_bind_int(p->pUpdate, i*3+2, !!pNew);
      if( pOld ){
        rc = sessionBindValue(p->pUpdate, i*3+1, pOld);
      }
      if( rc==SQLITE_OK && pNew ){
        rc = sessionBindValue(p->pUpdate, i*3+3, pNew);
      }
    }
    if( rc==SQLITE_OK ){
      sqlite3_bind_int(p->pUpdate, nCol*3+1, pbRetry==0 || pIter->bPatchset);
    }
    if( rc!=SQLITE_OK ) return rc;

    /* Attempt the UPDATE. In the case of a NOTFOUND or DATA conflict,
    ** the result will be SQLITE_OK with 0 rows modified. */
    sqlite3_step(p->pUpdate);
    rc = sqlite3_reset(p->pUpdate);

    if( rc==SQLITE_OK && sqlite3_changes(p->db)==0 ){
      /* A NOTFOUND or DATA error. Search the table to see if it contains
      ** a row with a matching primary key. If so, this is a DATA conflict.
      ** Otherwise, if there is no primary key match, it is a NOTFOUND. */

      rc = sessionConflictHandler(
          SQLITE_CHANGESET_DATA, p, pIter, xConflict, pCtx, pbRetry
      );

    }else if( (rc&0xff)==SQLITE_CONSTRAINT ){
      /* This is always a CONSTRAINT conflict. */
      rc = sessionConflictHandler(
          SQLITE_CHANGESET_CONFLICT, p, pIter, xConflict, pCtx, 0
      );
    }

  }else{
    assert( op==SQLITE_INSERT );
    rc = sessionBindRow(pIter, sqlite3changeset_new, nCol, 0, p->pInsert);
    if( rc!=SQLITE_OK ) return rc;

    sqlite3_step(p->pInsert);
    rc = sqlite3_reset(p->pInsert);
    if( (rc&0xff)==SQLITE_CONSTRAINT ){
      rc = sessionConflictHandler(
          SQLITE_CHANGESET_CONFLICT, p, pIter, xConflict, pCtx, pbReplace
      );
    }
  }

  return rc;
}

/*
** Attempt to apply the change that the iterator passed as the first argument
** currently points to to the database. If a conflict is encountered, invoke
** the conflict handler callback.
**
** The difference between this function and sessionApplyOne() is that this
** function handles the case where the conflict-handler is invoked and 
** returns SQLITE_CHANGESET_REPLACE - indicating that the change should be
** retried in some manner.
*/
static int sessionApplyOneWithRetry(
  sqlite3 *db,                    /* Apply change to "main" db of this handle */
  sqlite3_changeset_iter *pIter,  /* Changeset iterator to read change from */
  SessionApplyCtx *pApply,        /* Apply context */
  int(*xConflict)(void*, int, sqlite3_changeset_iter*),
  void *pCtx                      /* First argument passed to xConflict */
){
  int bReplace = 0;
  int bRetry = 0;
  int rc;

  rc = sessionApplyOneOp(pIter, pApply, xConflict, pCtx, &bReplace, &bRetry);
  assert( rc==SQLITE_OK || (bRetry==0 && bReplace==0) );

  /* If the bRetry flag is set, the change has not been applied due to an
  ** SQLITE_CHANGESET_DATA problem (i.e. this is an UPDATE or DELETE and
  ** a row with the correct PK is present in the db, but one or more other
  ** fields do not contain the expected values) and the conflict handler 
  ** returned SQLITE_CHANGESET_REPLACE. In this case retry the operation,
  ** but pass NULL as the final argument so that sessionApplyOneOp() ignores
  ** the SQLITE_CHANGESET_DATA problem.  */
  if( bRetry ){
    assert( pIter->op==SQLITE_UPDATE || pIter->op==SQLITE_DELETE );
    rc = sessionApplyOneOp(pIter, pApply, xConflict, pCtx, 0, 0);
  }

  /* If the bReplace flag is set, the change is an INSERT that has not
  ** been performed because the database already contains a row with the
  ** specified primary key and the conflict handler returned
  ** SQLITE_CHANGESET_REPLACE. In this case remove the conflicting row
  ** before reattempting the INSERT.  */
  else if( bReplace ){
    assert( pIter->op==SQLITE_INSERT );
    rc = sqlite3_exec(db, "SAVEPOINT replace_op", 0, 0, 0);
    if( rc==SQLITE_OK ){
      rc = sessionBindRow(pIter, 
          sqlite3changeset_new, pApply->nCol, pApply->abPK, pApply->pDelete);
      sqlite3_bind_int(pApply->pDelete, pApply->nCol+1, 1);
    }
    if( rc==SQLITE_OK ){
      sqlite3_step(pApply->pDelete);
      rc = sqlite3_reset(pApply->pDelete);
    }
    if( rc==SQLITE_OK ){
      rc = sessionApplyOneOp(pIter, pApply, xConflict, pCtx, 0, 0);
    }
    if( rc==SQLITE_OK ){
      rc = sqlite3_exec(db, "RELEASE replace_op", 0, 0, 0);
    }
  }

  return rc;
}

/*
** Retry the changes accumulated in the pApply->constraints buffer.
*/
static int sessionRetryConstraints(
  sqlite3 *db, 
  int bPatchset,
  const char *zTab,
  SessionApplyCtx *pApply,
  int(*xConflict)(void*, int, sqlite3_changeset_iter*),
  void *pCtx                      /* First argument passed to xConflict */
){
  int rc = SQLITE_OK;

  while( pApply->constraints.nBuf ){
    sqlite3_changeset_iter *pIter2 = 0;
    SessionBuffer cons = pApply->constraints;
    memset(&pApply->constraints, 0, sizeof(SessionBuffer));

    rc = sessionChangesetStart(&pIter2, 0, 0, cons.nBuf, cons.aBuf);
    if( rc==SQLITE_OK ){
      int nByte = 2*pApply->nCol*sizeof(sqlite3_value*);
      int rc2;
      pIter2->bPatchset = bPatchset;
      pIter2->zTab = (char*)zTab;
      pIter2->nCol = pApply->nCol;
      pIter2->abPK = pApply->abPK;
      sessionBufferGrow(&pIter2->tblhdr, nByte, &rc);
      pIter2->apValue = (sqlite3_value**)pIter2->tblhdr.aBuf;
      if( rc==SQLITE_OK ) memset(pIter2->apValue, 0, nByte);

      while( rc==SQLITE_OK && SQLITE_ROW==sqlite3changeset_next(pIter2) ){
        rc = sessionApplyOneWithRetry(db, pIter2, pApply, xConflict, pCtx);
      }

      rc2 = sqlite3changeset_finalize(pIter2);
      if( rc==SQLITE_OK ) rc = rc2;
    }
    assert( pApply->bDeferConstraints || pApply->constraints.nBuf==0 );

    sqlite3_free(cons.aBuf);
    if( rc!=SQLITE_OK ) break;
    if( pApply->constraints.nBuf>=cons.nBuf ){
      /* No progress was made on the last round. */
      pApply->bDeferConstraints = 0;
    }
  }

  return rc;
}

/*
** Argument pIter is a changeset iterator that has been initialized, but
** not yet passed to sqlite3changeset_next(). This function applies the 
** changeset to the main database attached to handle "db". The supplied
** conflict handler callback is invoked to resolve any conflicts encountered
** while applying the change.
*/
static int sessionChangesetApply(
  sqlite3 *db,                    /* Apply change to "main" db of this handle */
  sqlite3_changeset_iter *pIter,  /* Changeset to apply */
  int(*xFilter)(
    void *pCtx,                   /* Copy of sixth arg to _apply() */
    const char *zTab              /* Table name */
  ),
  int(*xConflict)(
    void *pCtx,                   /* Copy of fifth arg to _apply() */
    int eConflict,                /* DATA, MISSING, CONFLICT, CONSTRAINT */
    sqlite3_changeset_iter *p     /* Handle describing change and conflict */
  ),
  void *pCtx                      /* First argument passed to xConflict */
){
  int schemaMismatch = 0;
  int rc;                         /* Return code */
  const char *zTab = 0;           /* Name of current table */
  int nTab = 0;                   /* Result of sqlite3Strlen30(zTab) */
  SessionApplyCtx sApply;         /* changeset_apply() context object */
  int bPatchset;

  assert( xConflict!=0 );

  pIter->in.bNoDiscard = 1;
  memset(&sApply, 0, sizeof(sApply));
  sqlite3_mutex_enter(sqlite3_db_mutex(db));
  rc = sqlite3_exec(db, "SAVEPOINT changeset_apply", 0, 0, 0);
  if( rc==SQLITE_OK ){
    rc = sqlite3_exec(db, "PRAGMA defer_foreign_keys = 1", 0, 0, 0);
  }
  while( rc==SQLITE_OK && SQLITE_ROW==sqlite3changeset_next(pIter) ){
    int nCol;
    int op;
    const char *zNew;
    
    sqlite3changeset_op(pIter, &zNew, &nCol, &op, 0);

    if( zTab==0 || sqlite3_strnicmp(zNew, zTab, nTab+1) ){
      u8 *abPK;

      rc = sessionRetryConstraints(
          db, pIter->bPatchset, zTab, &sApply, xConflict, pCtx
      );
      if( rc!=SQLITE_OK ) break;

      sqlite3_free((char*)sApply.azCol);  /* cast works around VC++ bug */
      sqlite3_finalize(sApply.pDelete);
      sqlite3_finalize(sApply.pUpdate); 
      sqlite3_finalize(sApply.pInsert);
      sqlite3_finalize(sApply.pSelect);
      memset(&sApply, 0, sizeof(sApply));
      sApply.db = db;
      sApply.bDeferConstraints = 1;

      /* If an xFilter() callback was specified, invoke it now. If the 
      ** xFilter callback returns zero, skip this table. If it returns
      ** non-zero, proceed. */
      schemaMismatch = (xFilter && (0==xFilter(pCtx, zNew)));
      if( schemaMismatch ){
        zTab = sqlite3_mprintf("%s", zNew);
        if( zTab==0 ){
          rc = SQLITE_NOMEM;
          break;
        }
        nTab = (int)strlen(zTab);
        sApply.azCol = (const char **)zTab;
      }else{
        sqlite3changeset_pk(pIter, &abPK, 0);
        rc = sessionTableInfo(
            db, "main", zNew, &sApply.nCol, &zTab, &sApply.azCol, &sApply.abPK
        );
        if( rc!=SQLITE_OK ) break;
  
        if( sApply.nCol==0 ){
          schemaMismatch = 1;
          sqlite3_log(SQLITE_SCHEMA, 
              "sqlite3changeset_apply(): no such table: %s", zTab
          );
        }
        else if( sApply.nCol!=nCol ){
          schemaMismatch = 1;
          sqlite3_log(SQLITE_SCHEMA, 
              "sqlite3changeset_apply(): table %s has %d columns, expected %d", 
              zTab, sApply.nCol, nCol
          );
        }
        else if( memcmp(sApply.abPK, abPK, nCol)!=0 ){
          schemaMismatch = 1;
          sqlite3_log(SQLITE_SCHEMA, "sqlite3changeset_apply(): "
              "primary key mismatch for table %s", zTab
          );
        }
        else if( 
            (rc = sessionSelectRow(db, zTab, &sApply))
         || (rc = sessionUpdateRow(db, zTab, &sApply))
         || (rc = sessionDeleteRow(db, zTab, &sApply))
         || (rc = sessionInsertRow(db, zTab, &sApply))
        ){
          break;
        }
        nTab = sqlite3Strlen30(zTab);
      }
    }

    /* If there is a schema mismatch on the current table, proceed to the
    ** next change. A log message has already been issued. */
    if( schemaMismatch ) continue;

    rc = sessionApplyOneWithRetry(db, pIter, &sApply, xConflict, pCtx);
  }

  bPatchset = pIter->bPatchset;
  if( rc==SQLITE_OK ){
    rc = sqlite3changeset_finalize(pIter);
  }else{
    sqlite3changeset_finalize(pIter);
  }

  if( rc==SQLITE_OK ){
    rc = sessionRetryConstraints(db, bPatchset, zTab, &sApply, xConflict, pCtx);
  }

  if( rc==SQLITE_OK ){
    int nFk, notUsed;
    sqlite3_db_status(db, SQLITE_DBSTATUS_DEFERRED_FKS, &nFk, &notUsed, 0);
    if( nFk!=0 ){
      int res = SQLITE_CHANGESET_ABORT;
      sqlite3_changeset_iter sIter;
      memset(&sIter, 0, sizeof(sIter));
      sIter.nCol = nFk;
      res = xConflict(pCtx, SQLITE_CHANGESET_FOREIGN_KEY, &sIter);
      if( res!=SQLITE_CHANGESET_OMIT ){
        rc = SQLITE_CONSTRAINT;
      }
    }
  }
  sqlite3_exec(db, "PRAGMA defer_foreign_keys = 0", 0, 0, 0);

  if( rc==SQLITE_OK ){
    rc = sqlite3_exec(db, "RELEASE changeset_apply", 0, 0, 0);
  }else{
    sqlite3_exec(db, "ROLLBACK TO changeset_apply", 0, 0, 0);
    sqlite3_exec(db, "RELEASE changeset_apply", 0, 0, 0);
  }

  sqlite3_finalize(sApply.pInsert);
  sqlite3_finalize(sApply.pDelete);
  sqlite3_finalize(sApply.pUpdate);
  sqlite3_finalize(sApply.pSelect);
  sqlite3_free((char*)sApply.azCol);  /* cast works around VC++ bug */
  sqlite3_free((char*)sApply.constraints.aBuf);
  sqlite3_mutex_leave(sqlite3_db_mutex(db));
  return rc;
}

/*
** Apply the changeset passed via pChangeset/nChangeset to the main database
** attached to handle "db". Invoke the supplied conflict handler callback
** to resolve any conflicts encountered while applying the change.
*/
SQLITE_API int SQLITE_STDCALL sqlite3changeset_apply(
  sqlite3 *db,                    /* Apply change to "main" db of this handle */
  int nChangeset,                 /* Size of changeset in bytes */
  void *pChangeset,               /* Changeset blob */
  int(*xFilter)(
    void *pCtx,                   /* Copy of sixth arg to _apply() */
    const char *zTab              /* Table name */
  ),
  int(*xConflict)(
    void *pCtx,                   /* Copy of fifth arg to _apply() */
    int eConflict,                /* DATA, MISSING, CONFLICT, CONSTRAINT */
    sqlite3_changeset_iter *p     /* Handle describing change and conflict */
  ),
  void *pCtx                      /* First argument passed to xConflict */
){
  sqlite3_changeset_iter *pIter;  /* Iterator to skip through changeset */  
  int rc = sqlite3changeset_start(&pIter, nChangeset, pChangeset);
  if( rc==SQLITE_OK ){
    rc = sessionChangesetApply(db, pIter, xFilter, xConflict, pCtx);
  }
  return rc;
}

/*
** Apply the changeset passed via xInput/pIn to the main database
** attached to handle "db". Invoke the supplied conflict handler callback
** to resolve any conflicts encountered while applying the change.
*/
SQLITE_API int SQLITE_STDCALL sqlite3changeset_apply_strm(
  sqlite3 *db,                    /* Apply change to "main" db of this handle */
  int (*xInput)(void *pIn, void *pData, int *pnData), /* Input function */
  void *pIn,                                          /* First arg for xInput */
  int(*xFilter)(
    void *pCtx,                   /* Copy of sixth arg to _apply() */
    const char *zTab              /* Table name */
  ),
  int(*xConflict)(
    void *pCtx,                   /* Copy of sixth arg to _apply() */
    int eConflict,                /* DATA, MISSING, CONFLICT, CONSTRAINT */
    sqlite3_changeset_iter *p     /* Handle describing change and conflict */
  ),
  void *pCtx                      /* First argument passed to xConflict */
){
  sqlite3_changeset_iter *pIter;  /* Iterator to skip through changeset */  
  int rc = sqlite3changeset_start_strm(&pIter, xInput, pIn);
  if( rc==SQLITE_OK ){
    rc = sessionChangesetApply(db, pIter, xFilter, xConflict, pCtx);
  }
  return rc;
}

/*
** sqlite3_changegroup handle.
*/
struct sqlite3_changegroup {
  int rc;                         /* Error code */
  int bPatch;                     /* True to accumulate patchsets */
  SessionTable *pList;            /* List of tables in current patch */
};

/*
** This function is called to merge two changes to the same row together as
** part of an sqlite3changeset_concat() operation. A new change object is
** allocated and a pointer to it stored in *ppNew.
*/
static int sessionChangeMerge(
  SessionTable *pTab,             /* Table structure */
  int bPatchset,                  /* True for patchsets */
  SessionChange *pExist,          /* Existing change */
  int op2,                        /* Second change operation */
  int bIndirect,                  /* True if second change is indirect */
  u8 *aRec,                       /* Second change record */
  int nRec,                       /* Number of bytes in aRec */
  SessionChange **ppNew           /* OUT: Merged change */
){
  SessionChange *pNew = 0;

  if( !pExist ){
    pNew = (SessionChange *)sqlite3_malloc(sizeof(SessionChange) + nRec);
    if( !pNew ){
      return SQLITE_NOMEM;
    }
    memset(pNew, 0, sizeof(SessionChange));
    pNew->op = op2;
    pNew->bIndirect = bIndirect;
    pNew->nRecord = nRec;
    pNew->aRecord = (u8*)&pNew[1];
    memcpy(pNew->aRecord, aRec, nRec);
  }else{
    int op1 = pExist->op;

    /* 
    **   op1=INSERT, op2=INSERT      ->      Unsupported. Discard op2.
    **   op1=INSERT, op2=UPDATE      ->      INSERT.
    **   op1=INSERT, op2=DELETE      ->      (none)
    **
    **   op1=UPDATE, op2=INSERT      ->      Unsupported. Discard op2.
    **   op1=UPDATE, op2=UPDATE      ->      UPDATE.
    **   op1=UPDATE, op2=DELETE      ->      DELETE.
    **
    **   op1=DELETE, op2=INSERT      ->      UPDATE.
    **   op1=DELETE, op2=UPDATE      ->      Unsupported. Discard op2.
    **   op1=DELETE, op2=DELETE      ->      Unsupported. Discard op2.
    */   
    if( (op1==SQLITE_INSERT && op2==SQLITE_INSERT)
     || (op1==SQLITE_UPDATE && op2==SQLITE_INSERT)
     || (op1==SQLITE_DELETE && op2==SQLITE_UPDATE)
     || (op1==SQLITE_DELETE && op2==SQLITE_DELETE)
    ){
      pNew = pExist;
    }else if( op1==SQLITE_INSERT && op2==SQLITE_DELETE ){
      sqlite3_free(pExist);
      assert( pNew==0 );
    }else{
      u8 *aExist = pExist->aRecord;
      int nByte;
      u8 *aCsr;

      /* Allocate a new SessionChange object. Ensure that the aRecord[]
      ** buffer of the new object is large enough to hold any record that
      ** may be generated by combining the input records.  */
      nByte = sizeof(SessionChange) + pExist->nRecord + nRec;
      pNew = (SessionChange *)sqlite3_malloc(nByte);
      if( !pNew ){
        sqlite3_free(pExist);
        return SQLITE_NOMEM;
      }
      memset(pNew, 0, sizeof(SessionChange));
      pNew->bIndirect = (bIndirect && pExist->bIndirect);
      aCsr = pNew->aRecord = (u8 *)&pNew[1];

      if( op1==SQLITE_INSERT ){             /* INSERT + UPDATE */
        u8 *a1 = aRec;
        assert( op2==SQLITE_UPDATE );
        pNew->op = SQLITE_INSERT;
        if( bPatchset==0 ) sessionSkipRecord(&a1, pTab->nCol);
        sessionMergeRecord(&aCsr, pTab->nCol, aExist, a1);
      }else if( op1==SQLITE_DELETE ){       /* DELETE + INSERT */
        assert( op2==SQLITE_INSERT );
        pNew->op = SQLITE_UPDATE;
        if( bPatchset ){
          memcpy(aCsr, aRec, nRec);
          aCsr += nRec;
        }else{
          if( 0==sessionMergeUpdate(&aCsr, pTab, bPatchset, aExist, 0,aRec,0) ){
            sqlite3_free(pNew);
            pNew = 0;
          }
        }
      }else if( op2==SQLITE_UPDATE ){       /* UPDATE + UPDATE */
        u8 *a1 = aExist;
        u8 *a2 = aRec;
        assert( op1==SQLITE_UPDATE );
        if( bPatchset==0 ){
          sessionSkipRecord(&a1, pTab->nCol);
          sessionSkipRecord(&a2, pTab->nCol);
        }
        pNew->op = SQLITE_UPDATE;
        if( 0==sessionMergeUpdate(&aCsr, pTab, bPatchset, aRec, aExist,a1,a2) ){
          sqlite3_free(pNew);
          pNew = 0;
        }
      }else{                                /* UPDATE + DELETE */
        assert( op1==SQLITE_UPDATE && op2==SQLITE_DELETE );
        pNew->op = SQLITE_DELETE;
        if( bPatchset ){
          memcpy(aCsr, aRec, nRec);
          aCsr += nRec;
        }else{
          sessionMergeRecord(&aCsr, pTab->nCol, aRec, aExist);
        }
      }

      if( pNew ){
        pNew->nRecord = (int)(aCsr - pNew->aRecord);
      }
      sqlite3_free(pExist);
    }
  }

  *ppNew = pNew;
  return SQLITE_OK;
}

/*
** Add all changes in the changeset traversed by the iterator passed as
** the first argument to the changegroup hash tables.
*/
static int sessionChangesetToHash(
  sqlite3_changeset_iter *pIter,   /* Iterator to read from */
  sqlite3_changegroup *pGrp        /* Changegroup object to add changeset to */
){
  u8 *aRec;
  int nRec;
  int rc = SQLITE_OK;
  SessionTable *pTab = 0;


  while( SQLITE_ROW==sessionChangesetNext(pIter, &aRec, &nRec) ){
    const char *zNew;
    int nCol;
    int op;
    int iHash;
    int bIndirect;
    SessionChange *pChange;
    SessionChange *pExist = 0;
    SessionChange **pp;

    if( pGrp->pList==0 ){
      pGrp->bPatch = pIter->bPatchset;
    }else if( pIter->bPatchset!=pGrp->bPatch ){
      rc = SQLITE_ERROR;
      break;
    }

    sqlite3changeset_op(pIter, &zNew, &nCol, &op, &bIndirect);
    if( !pTab || sqlite3_stricmp(zNew, pTab->zName) ){
      /* Search the list for a matching table */
      int nNew = (int)strlen(zNew);
      u8 *abPK;

      sqlite3changeset_pk(pIter, &abPK, 0);
      for(pTab = pGrp->pList; pTab; pTab=pTab->pNext){
        if( 0==sqlite3_strnicmp(pTab->zName, zNew, nNew+1) ) break;
      }
      if( !pTab ){
        SessionTable **ppTab;

        pTab = sqlite3_malloc(sizeof(SessionTable) + nCol + nNew+1);
        if( !pTab ){
          rc = SQLITE_NOMEM;
          break;
        }
        memset(pTab, 0, sizeof(SessionTable));
        pTab->nCol = nCol;
        pTab->abPK = (u8*)&pTab[1];
        memcpy(pTab->abPK, abPK, nCol);
        pTab->zName = (char*)&pTab->abPK[nCol];
        memcpy(pTab->zName, zNew, nNew+1);

        /* The new object must be linked on to the end of the list, not
        ** simply added to the start of it. This is to ensure that the
        ** tables within the output of sqlite3changegroup_output() are in 
        ** the right order.  */
        for(ppTab=&pGrp->pList; *ppTab; ppTab=&(*ppTab)->pNext);
        *ppTab = pTab;
      }else if( pTab->nCol!=nCol || memcmp(pTab->abPK, abPK, nCol) ){
        rc = SQLITE_SCHEMA;
        break;
      }
    }

    if( sessionGrowHash(pIter->bPatchset, pTab) ){
      rc = SQLITE_NOMEM;
      break;
    }
    iHash = sessionChangeHash(
        pTab, (pIter->bPatchset && op==SQLITE_DELETE), aRec, pTab->nChange
    );

    /* Search for existing entry. If found, remove it from the hash table. 
    ** Code below may link it back in.
    */
    for(pp=&pTab->apChange[iHash]; *pp; pp=&(*pp)->pNext){
      int bPkOnly1 = 0;
      int bPkOnly2 = 0;
      if( pIter->bPatchset ){
        bPkOnly1 = (*pp)->op==SQLITE_DELETE;
        bPkOnly2 = op==SQLITE_DELETE;
      }
      if( sessionChangeEqual(pTab, bPkOnly1, (*pp)->aRecord, bPkOnly2, aRec) ){
        pExist = *pp;
        *pp = (*pp)->pNext;
        pTab->nEntry--;
        break;
      }
    }

    rc = sessionChangeMerge(pTab, 
        pIter->bPatchset, pExist, op, bIndirect, aRec, nRec, &pChange
    );
    if( rc ) break;
    if( pChange ){
      pChange->pNext = pTab->apChange[iHash];
      pTab->apChange[iHash] = pChange;
      pTab->nEntry++;
    }
  }

  if( rc==SQLITE_OK ) rc = pIter->rc;
  return rc;
}

/*
** Serialize a changeset (or patchset) based on all changesets (or patchsets)
** added to the changegroup object passed as the first argument.
**
** If xOutput is not NULL, then the changeset/patchset is returned to the
** user via one or more calls to xOutput, as with the other streaming
** interfaces. 
**
** Or, if xOutput is NULL, then (*ppOut) is populated with a pointer to a
** buffer containing the output changeset before this function returns. In
** this case (*pnOut) is set to the size of the output buffer in bytes. It
** is the responsibility of the caller to free the output buffer using
** sqlite3_free() when it is no longer required.
**
** If successful, SQLITE_OK is returned. Or, if an error occurs, an SQLite
** error code. If an error occurs and xOutput is NULL, (*ppOut) and (*pnOut)
** are both set to 0 before returning.
*/
static int sessionChangegroupOutput(
  sqlite3_changegroup *pGrp,
  int (*xOutput)(void *pOut, const void *pData, int nData),
  void *pOut,
  int *pnOut,
  void **ppOut
){
  int rc = SQLITE_OK;
  SessionBuffer buf = {0, 0, 0};
  SessionTable *pTab;
  assert( xOutput==0 || (ppOut==0 && pnOut==0) );

  /* Create the serialized output changeset based on the contents of the
  ** hash tables attached to the SessionTable objects in list p->pList. 
  */
  for(pTab=pGrp->pList; rc==SQLITE_OK && pTab; pTab=pTab->pNext){
    int i;
    if( pTab->nEntry==0 ) continue;

    sessionAppendTableHdr(&buf, pGrp->bPatch, pTab, &rc);
    for(i=0; i<pTab->nChange; i++){
      SessionChange *p;
      for(p=pTab->apChange[i]; p; p=p->pNext){
        sessionAppendByte(&buf, p->op, &rc);
        sessionAppendByte(&buf, p->bIndirect, &rc);
        sessionAppendBlob(&buf, p->aRecord, p->nRecord, &rc);
      }
    }

    if( rc==SQLITE_OK && xOutput && buf.nBuf>=SESSIONS_STRM_CHUNK_SIZE ){
      rc = xOutput(pOut, buf.aBuf, buf.nBuf);
      buf.nBuf = 0;
    }
  }

  if( rc==SQLITE_OK ){
    if( xOutput ){
      if( buf.nBuf>0 ) rc = xOutput(pOut, buf.aBuf, buf.nBuf);
    }else{
      *ppOut = buf.aBuf;
      *pnOut = buf.nBuf;
      buf.aBuf = 0;
    }
  }
  sqlite3_free(buf.aBuf);

  return rc;
}

/*
** Allocate a new, empty, sqlite3_changegroup.
*/
SQLITE_API int SQLITE_STDCALL sqlite3changegroup_new(sqlite3_changegroup **pp){
  int rc = SQLITE_OK;             /* Return code */
  sqlite3_changegroup *p;         /* New object */
  p = (sqlite3_changegroup*)sqlite3_malloc(sizeof(sqlite3_changegroup));
  if( p==0 ){
    rc = SQLITE_NOMEM;
  }else{
    memset(p, 0, sizeof(sqlite3_changegroup));
  }
  *pp = p;
  return rc;
}

/*
** Add the changeset currently stored in buffer pData, size nData bytes,
** to changeset-group p.
*/
SQLITE_API int SQLITE_STDCALL sqlite3changegroup_add(sqlite3_changegroup *pGrp, int nData, void *pData){
  sqlite3_changeset_iter *pIter;  /* Iterator opened on pData/nData */
  int rc;                         /* Return code */

  rc = sqlite3changeset_start(&pIter, nData, pData);
  if( rc==SQLITE_OK ){
    rc = sessionChangesetToHash(pIter, pGrp);
  }
  sqlite3changeset_finalize(pIter);
  return rc;
}

/*
** Obtain a buffer containing a changeset representing the concatenation
** of all changesets added to the group so far.
*/
SQLITE_API int SQLITE_STDCALL sqlite3changegroup_output(
    sqlite3_changegroup *pGrp,
    int *pnData,
    void **ppData
){
  return sessionChangegroupOutput(pGrp, 0, 0, pnData, ppData);
}

/*
** Streaming versions of changegroup_add().
*/
SQLITE_API int SQLITE_STDCALL sqlite3changegroup_add_strm(
  sqlite3_changegroup *pGrp,
  int (*xInput)(void *pIn, void *pData, int *pnData),
  void *pIn
){
  sqlite3_changeset_iter *pIter;  /* Iterator opened on pData/nData */
  int rc;                         /* Return code */

  rc = sqlite3changeset_start_strm(&pIter, xInput, pIn);
  if( rc==SQLITE_OK ){
    rc = sessionChangesetToHash(pIter, pGrp);
  }
  sqlite3changeset_finalize(pIter);
  return rc;
}

/*
** Streaming versions of changegroup_output().
*/
SQLITE_API int SQLITE_STDCALL sqlite3changegroup_output_strm(
  sqlite3_changegroup *pGrp,
  int (*xOutput)(void *pOut, const void *pData, int nData), 
  void *pOut
){
  return sessionChangegroupOutput(pGrp, xOutput, pOut, 0, 0);
}

/*
** Delete a changegroup object.
*/
SQLITE_API void SQLITE_STDCALL sqlite3changegroup_delete(sqlite3_changegroup *pGrp){
  if( pGrp ){
    sessionDeleteTable(pGrp->pList);
    sqlite3_free(pGrp);
  }
}

/* 
** Combine two changesets together.
*/
SQLITE_API int SQLITE_STDCALL sqlite3changeset_concat(
  int nLeft,                      /* Number of bytes in lhs input */
  void *pLeft,                    /* Lhs input changeset */
  int nRight                      /* Number of bytes in rhs input */,
  void *pRight,                   /* Rhs input changeset */
  int *pnOut,                     /* OUT: Number of bytes in output changeset */
  void **ppOut                    /* OUT: changeset (left <concat> right) */
){
  sqlite3_changegroup *pGrp;
  int rc;

  rc = sqlite3changegroup_new(&pGrp);
  if( rc==SQLITE_OK ){
    rc = sqlite3changegroup_add(pGrp, nLeft, pLeft);
  }
  if( rc==SQLITE_OK ){
    rc = sqlite3changegroup_add(pGrp, nRight, pRight);
  }
  if( rc==SQLITE_OK ){
    rc = sqlite3changegroup_output(pGrp, pnOut, ppOut);
  }
  sqlite3changegroup_delete(pGrp);

  return rc;
}

/*
** Streaming version of sqlite3changeset_concat().
*/
SQLITE_API int SQLITE_STDCALL sqlite3changeset_concat_strm(
  int (*xInputA)(void *pIn, void *pData, int *pnData),
  void *pInA,
  int (*xInputB)(void *pIn, void *pData, int *pnData),
  void *pInB,
  int (*xOutput)(void *pOut, const void *pData, int nData),
  void *pOut
){
  sqlite3_changegroup *pGrp;
  int rc;

  rc = sqlite3changegroup_new(&pGrp);
  if( rc==SQLITE_OK ){
    rc = sqlite3changegroup_add_strm(pGrp, xInputA, pInA);
  }
  if( rc==SQLITE_OK ){
    rc = sqlite3changegroup_add_strm(pGrp, xInputB, pInB);
  }
  if( rc==SQLITE_OK ){
    rc = sqlite3changegroup_output_strm(pGrp, xOutput, pOut);
  }
  sqlite3changegroup_delete(pGrp);

  return rc;
}

#endif /* SQLITE_ENABLE_SESSION && SQLITE_ENABLE_PREUPDATE_HOOK */

/************** End of sqlite3session.c **************************************/
/************** Begin file json1.c *******************************************/
/*
** 2015-08-12
**
** The author disclaims copyright to this source code.  In place of
** a legal notice, here is a blessing:
**