public function deleteRegistrationsOnCollection(\collection $collection)
    {
        $qb = $this->repository->createQueryBuilder('d');
        $qb->delete('Phraseanet:Registration', 'd');
        $qb->where($qb->expr()->eq('d.baseId', ':base'));
        $qb->setParameter(':base', $collection->get_base_id());
        $qb->getQuery()->execute();
    }