private function &getCollection()
    {
        if (null === $this->collection) {
            $qb = $this->createAndFilterQueryBuilder($this->getEntityAlias());
            if ($this->isHydrationDisabled()) {
                $this->collection = $qb->getQuery()->getScalarResult();
            } else {
                $this->collection = $qb->getQuery()->getResult();
            }
        }
        return $this->collection;
    }