SQLite

  sqlite3_int64 iIntkey;          /* Integer key value */
};

/* The sqlite_dbdata table */
struct DbdataTable {
  sqlite3_vtab base;              /* Base class.  Must be first */
  sqlite3 *db;                    /* The database connection */
  sqlite3_stmt *pStmt;            /* For fetching database pages */
  int bPtr;                       /* True for sqlite3_dbptr table */
};

#define DBDATA_COLUMN_PGNO        0
#define DBDATA_COLUMN_CELL        1
#define DBDATA_COLUMN_FIELD       2
#define DBDATA_COLUMN_VALUE       3

  return rc;
}

/*
** Disconnect from or destroy a dbdata virtual table.
*/
static int dbdataDisconnect(sqlite3_vtab *pVtab){
  DbdataTable *pTab = (DbdataTable*)pVtab;
  if( pTab ){
    sqlite3_finalize(pTab->pStmt);
    sqlite3_free(pVtab);
  }
  return SQLITE_OK;
}

/*
**
** This function interprets two types of constraints:
**
**       schema=?
**       pgno=?
**
** If neither are present, idxNum is set to 0. If schema=? is present,
** the 0x01 bit in idxNum is set. If pgno=? is present, the 0x02 bit
** in idxNum is set.
**
** If both parameters are present, schema is in position 0 and pgno in
** position 1.
*/
static int dbdataBestIndex(sqlite3_vtab *tab, sqlite3_index_info *pIdx){
  DbdataTable *pTab = (DbdataTable*)tab;
  int i;
  int iSchema = -1;
  int iPgno = -1;
  int colSchema = (pTab->bPtr ? DBPTR_COLUMN_SCHEMA : DBDATA_COLUMN_SCHEMA);

  for(i=0; i<pIdx->nConstraint; i++){
    struct sqlite3_index_constraint *p = &pIdx->aConstraint[i];
    if( p->op==SQLITE_INDEX_CONSTRAINT_EQ ){
      if( p->iColumn==colSchema ){
        if( p->usable==0 ) return SQLITE_CONSTRAINT;
        iSchema = i;
      }
      if( p->iColumn==DBDATA_COLUMN_PGNO && p->usable ){
        iPgno = i;
      }
    }
  }

  if( iSchema>=0 ){
    pIdx->aConstraintUsage[iSchema].argvIndex = 1;
    pIdx->aConstraintUsage[iSchema].omit = 1;
  }
  if( iPgno>=0 ){
    pIdx->aConstraintUsage[iPgno].argvIndex = 1 + (iSchema>=0);
    pIdx->aConstraintUsage[iPgno].omit = 1;
    pIdx->estimatedCost = 100;
    pIdx->estimatedRows =  50;

    if( pTab->bPtr==0 && pIdx->nOrderBy && pIdx->aOrderBy[0].desc==0 ){
      int iCol = pIdx->aOrderBy[0].iColumn;
      if( pIdx->nOrderBy==1 ){
        pIdx->orderByConsumed = (iCol==0 || iCol==1);
      }else if( pIdx->nOrderBy==2 && pIdx->aOrderBy[1].desc==0 && iCol==0 ){
        pIdx->orderByConsumed = (pIdx->aOrderBy[1].iColumn==1);
      }
    }

  }else{
    pIdx->estimatedCost = 100000000;
    pIdx->estimatedRows = 1000000000;
  }
  pIdx->idxNum = (iSchema>=0 ? 0x01 : 0x00) | (iPgno>=0 ? 0x02 : 0x00);
  return SQLITE_OK;
}

/*
** Open a new dbdata cursor.
*/
static int dbdataOpen(sqlite3_vtab *pVTab, sqlite3_vtab_cursor **ppCursor){

  }

  *ppCursor = (sqlite3_vtab_cursor *)pCsr;
  return SQLITE_OK;
}

static void dbdataResetCursor(DbdataCursor *pCsr){
  DbdataTable *pTab = (DbdataTable*)(pCsr->base.pVtab);
  if( pTab->pStmt==0 ){
    pTab->pStmt = pCsr->pStmt;
  }else{
    sqlite3_finalize(pCsr->pStmt);
  }
  pCsr->pStmt = 0;
  pCsr->iPgno = 1;
  pCsr->iCell = 0;
  pCsr->iField = 0;
  pCsr->bOnePage = 0;
}

static int dbdataFilter(
  sqlite3_vtab_cursor *pCursor, 
  int idxNum, const char *idxStr,
  int argc, sqlite3_value **argv
){
  DbdataCursor *pCsr = (DbdataCursor*)pCursor;
  DbdataTable *pTab = (DbdataTable*)pCursor->pVtab;
  int rc = SQLITE_OK;
  const char *zSchema = "main";

  dbdataResetCursor(pCsr);
  assert( pCsr->iPgno==1 );
  if( idxNum & 0x01 ){
    zSchema = (const char*)sqlite3_value_text(argv[0]);
  }
  if( idxNum & 0x02 ){
    pCsr->iPgno = sqlite3_value_int(argv[(idxNum & 0x01)]);
    pCsr->bOnePage = 1;
  }

  if( pTab->pStmt ){
    pCsr->pStmt = pTab->pStmt;
    pTab->pStmt = 0;
  }else{
    rc = sqlite3_prepare_v2(pTab->db, 
        "SELECT data FROM sqlite_dbpage(?) WHERE pgno=?", -1,
        &pCsr->pStmt, 0
    );
  }
  if( rc==SQLITE_OK ){
    rc = sqlite3_bind_text(pCsr->pStmt, 1, zSchema, -1, SQLITE_TRANSIENT);
  }else{
    pTab->base.zErrMsg = sqlite3_mprintf("%s", sqlite3_errmsg(pTab->db));
  }
  if( rc==SQLITE_OK ){
    rc = dbdataNext(pCursor);

** This function is called to recover data from the database. A script
** to construct a new database containing all recovered data is output
** on stream pState->out.
*/
static int recoverDatabaseCmd(ShellState *pState){
  int rc = SQLITE_OK;
  sqlite3_stmt *pLoop = 0;        /* Loop through all root pages */
  sqlite3_stmt *pPages = 0;       /* Loop through all pages in a group */
  sqlite3_stmt *pCells = 0;       /* Loop through all cells in a page */

  shellExec(pState->db, &rc, 
    /* Attach an in-memory database named 'recovery'. Create an indexed 
    ** cache of the sqlite_dbptr virtual table. */
    "ATTACH '' AS recovery;"
    "CREATE TABLE recovery.dbptr("
    "      pgno, child, PRIMARY KEY(child, pgno)"

      const char *zCreateTable = (const char*)sqlite3_column_text(pStmt, 0);
      raw_printf(pState->out, "CREATE TABLE IF NOT EXISTS %s;\n", 
          &zCreateTable[12]
      );
    }
    shellFinalize(&rc, pStmt);
  }

  shellPrepare(pState->db, &rc,
      "SELECT pgno FROM recovery.map WHERE root=?", &pPages
  );
  shellPrepare(pState->db, &rc,
      "SELECT max(field), group_concat(shell_escape_crnl(quote(value)), ', ')"
      "FROM sqlite_dbdata WHERE pgno = ? AND field != ?"
      "GROUP BY cell", &pCells
  );

  /* Loop through each root page. */
  shellPrepare(pState->db, &rc, 
      "SELECT root, intkey, max(maxlen) FROM recovery.map" 
      " WHERE root>1 GROUP BY root, intkey ORDER BY root=("
      "  SELECT rootpage FROM recovery.schema WHERE name='sqlite_sequence'"
      ")", &pLoop
  );
  while( rc==SQLITE_OK && SQLITE_ROW==sqlite3_step(pLoop) ){
    int iRoot = sqlite3_column_int(pLoop, 0);
    int bIntkey = sqlite3_column_int(pLoop, 1);
    int nCol = sqlite3_column_int(pLoop, 2);
    RecoverTable *pTab;

    pTab = recoverNewTable(pState, &rc, iRoot, bIntkey, nCol);
    if( pTab ){

      if( 0==sqlite3_stricmp(pTab->zName, "sqlite_sequence") ){
        raw_printf(pState->out, "DELETE FROM sqlite_sequence;\n");
      }


      sqlite3_bind_int(pPages, 1, iRoot);



      sqlite3_bind_int(pCells, 2, pTab->iPk);

      while( rc==SQLITE_OK && SQLITE_ROW==sqlite3_step(pPages) ){
        sqlite3_bind_int(pCells, 1, sqlite3_column_int(pPages, 0));
        while( rc==SQLITE_OK && SQLITE_ROW==sqlite3_step(pCells) ){
          int iMax = sqlite3_column_int(pCells, 0);
          const char *zVal = (const char*)sqlite3_column_text(pCells, 1);
          raw_printf(pState->out, "INSERT INTO %s(%s) VALUES( %s );\n", 
              pTab->zQuoted, pTab->azlCol[iMax>0?iMax:0], zVal
          );
        }
        shellReset(&rc, pCells);
      }
      shellReset(&rc, pPages);
    }
    recoverFreeTable(pTab);
  }
  shellFinalize(&rc, pLoop);
  shellFinalize(&rc, pPages);
  shellFinalize(&rc, pCells);

  /* The rest of the schema */
  if( rc==SQLITE_OK ){
    sqlite3_stmt *pStmt = 0;
    shellPrepare(pState->db, &rc, 
        "SELECT sql, name FROM recovery.schema "
        "WHERE sql NOT LIKE 'create table%'", &pStmt