private function printList($list)
    {
        $result = "";
        $comma = 0;
        for ($i = 0, $_i = count($list); $i < $_i; $i++) {
            $col = $list[$i];
            if ($col->isPrimaryKey()) {
                $result .= ($comma++ ? ',' : '') . $this->getDatabase()->getPlatform()->quoteIdentifier($col->getName());
            }
        }

        return $result;
    }