SQLite

  unsigned char *abTblPk;         /* Array of flags, set on target PK columns */
  int eType;                      /* Table type - an OTA_PK_XXX value */

  /* Output variables. zTbl==0 implies EOF. */
  int bCleanup;                   /* True in "cleanup" state */
  const char *zTbl;               /* Name of target db table */
  const char *zIdx;               /* Name of target db index (or null) */
  int tnum;                       /* Root page of index (not table) */
  int iTnum;                      /* Root page of current object */
  int iPkTnum;                    /* If eType==EXTERNAL, root of PK index */
  int bUnique;                    /* Current index is unique */
  int iVisit;                     /* Number of points visited, incl. current */

  /* Statements created by otaObjIterPrepareAll() */
  int nCol;                       /* Number of columns in current object */
  sqlite3_stmt *pSelect;          /* Source data */
  sqlite3_stmt *pInsert;          /* Statement for INSERT operations */

        pIter->bCleanup = 0;
        rc = sqlite3_step(pIter->pTblIter);
        if( rc!=SQLITE_ROW ){
          rc = sqlite3_reset(pIter->pTblIter);
          pIter->zTbl = 0;
        }else{
          pIter->zTbl = (const char*)sqlite3_column_text(pIter->pTblIter, 0);
          pIter->tnum = sqlite3_column_int(pIter->pTblIter, 1);
          pIter->iTnum = sqlite3_column_int(pIter->pTblIter, 1);
          rc = SQLITE_OK;
        }
      }else{
        if( pIter->zIdx==0 ){
          sqlite3_bind_text(pIter->pIdxIter, 1, pIter->zTbl, -1, SQLITE_STATIC);
        }
        rc = sqlite3_step(pIter->pIdxIter);
        if( rc!=SQLITE_ROW ){
          rc = sqlite3_reset(pIter->pIdxIter);
          pIter->bCleanup = 1;
          pIter->zIdx = 0;
        }else{
          pIter->zIdx = (const char*)sqlite3_column_text(pIter->pIdxIter, 0);
          pIter->tnum = sqlite3_column_int(pIter->pIdxIter, 1);
          pIter->iTnum = sqlite3_column_int(pIter->pIdxIter, 1);
          pIter->bUnique = sqlite3_column_int(pIter->pIdxIter, 2);
          rc = SQLITE_OK;
        }
      }
    }
  }

    int rc2;                      /* sqlite3_finalize() return value */
    int bOtaRowid = 0;            /* If input table has column "ota_rowid" */
    int iOrder = 0;

    /* Figure out the type of table this step will deal with. */
    assert( pIter->eType==0 );
    sqlite3_test_control(
        SQLITE_TESTCTRL_TBLTYPE, p->db, "main", pIter->zTbl, &pIter->eType
        SQLITE_TESTCTRL_TBLTYPE, p->db, "main", pIter->zTbl, &pIter->eType,
        &pIter->iPkTnum
    );
    assert( pIter->eType==OTA_PK_NONE || pIter->eType==OTA_PK_IPK 
         || pIter->eType==OTA_PK_EXTERNAL || pIter->eType==OTA_PK_WITHOUT_ROWID
         || pIter->eType==OTA_PK_VTAB
    );

    /* Populate the azTblCol[] and nTblCol variables based on the columns

static char *otaObjIterGetWhere(
  sqlite3ota *p, 
  OtaObjIter *pIter
){
  char *zList = 0;
  if( pIter->eType==OTA_PK_VTAB || pIter->eType==OTA_PK_NONE ){
    zList = otaMPrintf(p, "_rowid_ = ?%d", pIter->nTblCol+1);
  }else if( pIter->eType==OTA_PK_EXTERNAL ){
    const char *zSep = "";
    int i;
    for(i=0; i<pIter->nTblCol; i++){
      if( pIter->abTblPk[i] ){
        zList = otaMPrintf(p, "%z%sc%d=?%d", zList, zSep, i, i+1);
        zSep = " AND ";
      }
    }
    zList = otaMPrintf(p, 
        "_rowid_ = (SELECT id FROM ota_imposter2 WHERE %z)", zList
    );

  }else{
    const char *zSep = "";
    int i;
    for(i=0; i<pIter->nTblCol; i++){
      if( pIter->abTblPk[i] ){
        const char *zCol = pIter->azTblCol[i];
        zList = otaMPrintf(p, "%z%s\"%w\"=?%d", zList, zSep, zCol, i+1);

    z = otaMPrintf(p, "%z)", z);

    rc = sqlite3_finalize(pXInfo);
    if( p->rc==SQLITE_OK ) p->rc = rc;
  }
  return z;
}

static void otaCreateImposterTable2(sqlite3ota *p, OtaObjIter *pIter){
  if( p->rc==SQLITE_OK && pIter->eType==OTA_PK_EXTERNAL ){
    int tnum = pIter->iPkTnum;    /* Root page of PK index */
    sqlite3_stmt *pQuery = 0;     /* SELECT name ... WHERE rootpage = $tnum */
    const char *zIdx = 0;         /* Name of PK index */
    sqlite3_stmt *pXInfo = 0;     /* PRAGMA main.index_xinfo = $zIdx */
    int rc;

    const char *zComma = "";

    char *zCols = 0;              /* Used to build up list of table cols */
    char *zPk = 0;                /* Used to build up table PK declaration */
    char *zSql = 0;               /* CREATE TABLE statement */

    /* Figure out the name of the primary key index for the current table.
    ** This is needed for the argument to "PRAGMA index_xinfo". Set
    ** zIdx to point to a nul-terminated string containing this name. */
    p->rc = prepareAndCollectError(p->db, &pQuery, &p->zErrmsg, 
        "SELECT name FROM sqlite_master WHERE rootpage = ?"
    );
    if( p->rc==SQLITE_OK ){
      sqlite3_bind_int(pQuery, 1, tnum);
      if( SQLITE_ROW==sqlite3_step(pQuery) ){
        zIdx = (const char*)sqlite3_column_text(pQuery, 0);
      }
      if( zIdx==0 ){
        p->rc = SQLITE_CORRUPT;
      }
    }
    assert( (zIdx==0)==(p->rc!=SQLITE_OK) );

    if( p->rc==SQLITE_OK ){
      p->rc = prepareFreeAndCollectError(p->db, &pXInfo, &p->zErrmsg,
          sqlite3_mprintf("PRAGMA main.index_xinfo = %Q", zIdx)
      );
    }
    sqlite3_finalize(pQuery);

    while( p->rc==SQLITE_OK && SQLITE_ROW==sqlite3_step(pXInfo) ){
      int bKey = sqlite3_column_int(pXInfo, 5);
      if( bKey ){
        int iCid = sqlite3_column_int(pXInfo, 1);
        int bDesc = sqlite3_column_int(pXInfo, 3);
        const char *zCollate = (const char*)sqlite3_column_text(pXInfo, 4);
        zCols = otaMPrintf(p, "%z%sc%d %s COLLATE %s", zCols, zComma, 
            iCid, pIter->azTblType[iCid], zCollate
        );
        zPk = otaMPrintf(p, "%z%sc%d%s", zPk, zComma, iCid, bDesc?" DESC":"");
        zComma = ", ";
      }
    }
    zCols = otaMPrintf(p, "%z, id INTEGER", zCols);
    rc = sqlite3_finalize(pXInfo);
    if( p->rc==SQLITE_OK ) p->rc = rc;

    zSql = otaMPrintf(p, 
        "CREATE TABLE ota_imposter2(%z, PRIMARY KEY(%z)) WITHOUT ROWID", 
        zCols, zPk
    );
    assert( (zSql==0)==(p->rc!=SQLITE_OK) );
    if( zSql ){
      sqlite3_test_control(SQLITE_TESTCTRL_IMPOSTER, p->db, "main", 1, tnum);
      p->rc = sqlite3_exec(p->db, zSql, 0, 0, &p->zErrmsg);
      sqlite3_test_control(SQLITE_TESTCTRL_IMPOSTER, p->db, "main", 0, 0);
    }
    sqlite3_free(zSql);
  }
}

/*
** If an error has already occurred when this function is called, it 
** immediately returns zero (without doing any work). Or, if an error
** occurs during the execution of this function, it sets the error code
** in the sqlite3ota object indicated by the first argument and returns
** zero.

**     precisely, the "same schema" means the same columns, types, collation
**     sequences and primary key declaration.
**
**   OTA_PK_VTAB:
**     No imposters required. 
**
**   OTA_PK_EXTERNAL:
**     Two imposters are required (TODO!!)
**     Two imposters are required. The first has the same schema as the
**     target database table, with no PRIMARY KEY or UNIQUE clauses. The
**     second is used to access the PK b-tree index on disk.
*/
static void otaCreateImposterTable(sqlite3ota *p, OtaObjIter *pIter){
  if( p->rc==SQLITE_OK && pIter->eType!=OTA_PK_VTAB ){
    int tnum = pIter->tnum;
    int tnum = pIter->iTnum;
    const char *zComma = "";
    char *zSql = 0;
    int iCol;
    sqlite3_test_control(SQLITE_TESTCTRL_IMPOSTER, p->db, "main", 0, 1);

    for(iCol=0; p->rc==SQLITE_OK && iCol<pIter->nTblCol; iCol++){
      const char *zPk = "";

static int otaObjIterPrepareAll(
  sqlite3ota *p, 
  OtaObjIter *pIter,
  int nOffset                     /* Add "LIMIT -1 OFFSET $nOffset" to SELECT */
){
  assert( pIter->bCleanup==0 );
  if( pIter->pSelect==0 && otaObjIterCacheTableInfo(p, pIter)==SQLITE_OK ){
    const int tnum = pIter->tnum;
    const int tnum = pIter->iTnum;
    char *zCollist = 0;           /* List of indexed columns */
    char **pz = &p->zErrmsg;
    const char *zIdx = pIter->zIdx;
    char *zLimit = 0;

    if( nOffset ){
      zLimit = sqlite3_mprintf(" LIMIT -1 OFFSET %d", nOffset);

              zCollist, (bOtaRowid ? ", ota_rowid" : ""), zTbl, zLimit
            )
        );
      }

      /* Create the imposter table or tables (if required). */
      otaCreateImposterTable(p, pIter);
      otaCreateImposterTable2(p, pIter);
      zWrite = (pIter->eType==OTA_PK_VTAB ? zTbl : "ota_imposter");

      /* Create the INSERT statement to write to the target PK b-tree */
      if( p->rc==SQLITE_OK ){
        p->rc = prepareFreeAndCollectError(p->db, &pIter->pInsert, pz,
            sqlite3_mprintf(
              "INSERT INTO main.%Q(%s%s) VALUES(%s)", 

    case 2: /* create_ota_delta */ {
      sqlite3 *db = sqlite3ota_db(pOta);
      int rc = sqlite3_create_function(
          db, "ota_delta", -1, SQLITE_UTF8, (void*)interp, test_ota_delta, 0, 0
      );
      Tcl_SetObjResult(interp, Tcl_NewStringObj(sqlite3ErrName(rc), -1));
      sqlite3_exec(db, "PRAGMA vdbe_trace = 1", 0, 0, 0);
      ret = (rc==SQLITE_OK ? TCL_OK : TCL_ERROR);
      break;
    }

    default: /* seems unlikely */
      assert( !"cannot happen" );
      break;

      if( db->init.busy==0 && db->init.newTnum>0 ){
        sqlite3ResetAllSchemasOfConnection(db);
      }
      sqlite3_mutex_leave(db->mutex);
      break;
    }

    /* sqlite3_test_control(SQLITE_TESTCTRL_TBLTYPE, db, dbName, zTbl, peType)
    /* sqlite3_test_control(TESTCTRL_TBLTYPE, db, dbName, zTbl, peType, piPk)
    **
    **   peType is of type (int*), a pointer to an output parameter of type
    **   (int). This call sets the output parameter as follows, depending
    **   on the type of the table specified by parameters dbName and zTbl.
    **
    **     0: No such table.
    **     1: Table has an implicit rowid.
    **     2: Table has an explicit IPK column.
    **     3: Table has an external PK index.
    **     4: Table is WITHOUT ROWID.
    **     5: Table is a virtual table.
    **
    **   Argument *piPk is also of type (int*), and also points to an output
    **   parameter. Unless the table has an external primary key index 
    **   (i.e. unless *peType is set to 3), then *piPk is set to zero. Or,
    **   if the table does have an external primary key index, then *piPk
    **   is set to the root page number of the primary key index before
    **   returning.
    */
    case SQLITE_TESTCTRL_TBLTYPE: {
      sqlite3 *db = va_arg(ap, sqlite3*);
      const char *zDb = va_arg(ap, const char*);
      const char *zTab = va_arg(ap, const char*);
      int *peType = va_arg(ap, int*);
      int *piPk = va_arg(ap, int*);
      Table *pTab;
      *piPk = 0;
      sqlite3_mutex_enter(db->mutex);
      sqlite3BtreeEnterAll(db);
      pTab = sqlite3FindTable(db, zTab, zDb);
      if( pTab==0 ){
        *peType = 0;
      }else if( IsVirtual(pTab) ){
        *peType = 5;
      }else if( HasRowid(pTab)==0 ){
        *peType = 4;
      }else if( pTab->iPKey>=0 ){
        *peType = 2;
      }else{
        Index *pPk = sqlite3PrimaryKeyIndex(pTab);
        if( pPk ){
        *peType = (pPk ? 3 : 1);
          *peType = 3;
          *piPk = pPk->tnum;
        }else{
          *peType = 1;
        }
      }
      sqlite3BtreeLeaveAll(db);
      sqlite3_mutex_leave(db->mutex);
      break;
    }
  }
  va_end(ap);