private function buildDeleteQuery(EntityManagerInterface $em)
    {
        $qb = $em->createQueryBuilder()
            ->delete($this->sharingClass, 's')
        ;

        $this->buildCriteria($qb, $this->deleteSharingSubjects, 'subjectClass', 'subjectId');
        $this->buildCriteria($qb, $this->deleteSharingIdentities, 'identityClass', 'identityName');

        return $qb->getQuery();
    }