public function get_row_format_sql($engine = null, $collation = null) {

        if (!isset($engine)) {
            $engine = $this->get_dbengine();
        }
        $engine = strtolower($engine);

        if (!isset($collation)) {
            $collation = $this->get_dbcollation();
        }

        $rowformat = '';
        if (($engine === 'innodb' || $engine === 'xtradb') && strpos($collation, 'utf8mb4_') === 0) {
            if ($this->is_compressed_row_format_supported()) {
                $rowformat = "ROW_FORMAT=Compressed";
            } else {
                $rowformat = "ROW_FORMAT=Dynamic";
            }
        }
        return $rowformat;
    }