public function findCrashedExports(\DateTime $before = null)
    {
        $qb = $this->createQueryBuilder('e');
        $qb->where($qb->expr()->gte('e.crash', 'e.nbretry'));

        if (null !== $before) {
            $qb->andWhere($qb->expr()->lte('e.created', ':created'));
            $qb->setParameter(':created', $before);
        }

        return $qb->getQuery()->getResult();
    }