code: function() {
        var has_created = updated_count == schema.stores.length;
        if (!executed) {
          // success callback without actually executing
          goog.log.warning(me.logger, dbname + ': ' + action + ' voided.');
          //if (!me.df_sql_db_.hasFired()) { // FIXME: why need to check ?
          // this checking is necessary when browser prompt user,
          // this migration function run two times: one creating table
          // and one without creating table. How annoying ?
          // testing is in /test/test_multi_storage.html page.
        } else {
          var msg = '.';
          if (updated_count != schema.stores.length) {
            msg = ' but unexpected stores exists.';
          }
          goog.log.finest(me.logger, dbname + ':' + db.version + ' ready' + msg);
          setDb(db);
        }
      }
docs: SQLVoidCallback