Doctrine_Search:readTableData method is supposed to return array of record ids, which are not indexed

$query = 'SELECT * FROM ' . $conn->quoteIdentifier($tableName)
               . ' WHERE ' . $conn->quoteIdentifier($id)
               . ' IN (SELECT ' . $conn->quoteIdentifier($id)
               . ' FROM ' . $conn->quoteIdentifier($this->_table->getTableName())
               . ' WHERE keyword IS NULL)';

this query always returns empty array, i think, it should be replaced by something like

$query = 'SELECT * FROM ' . $conn->quoteIdentifier($tableName)
               . ' WHERE ' . $conn->quoteIdentifier($id)
               . ' NOT IN (SELECT ' . $conn->quoteIdentifier($id)
               . ' FROM ' . $conn->quoteIdentifier($this->_table->getTableName()) . ')';