protected function _getIdentColNames()
    {
        $aColNames = $this->_getColNames();
        $aCols = [];
        foreach ($aColNames as $iKey => $aCol) {
            // ident ?
            if ($aCol[4]) {
                $aCols[$iKey] = $aCol;
            }
        }

        return $aCols;
    }