public function getParentContentUidByUid($contentUid)
    {
        $q = $this->_em->getConnection()
                ->createQueryBuilder()
                ->select('c.parent_uid')
                ->from('content_has_subcontent', 'c')
                ->where('c.content_uid = :uid')
                ->setParameter('uid', $contentUid);

        return $q->execute()->fetchAll(\PDO::FETCH_COLUMN);
    }