public function isQueued($alias)
    {
        $query = $this->createQueryBuilder('c')
            ->where('c.alias = :alias')
            ->andWhere('c.ended is NULL')
            ->setParameter('alias', $alias)
            ->getQuery();

        $result = $query->setMaxResults(1)->getOneOrNullResult();

        if ($result)
            return true;

        return false;
    }