[Flow] Find all Objects with an empty Collection

[David Sporer]

Hi,
I have a Model containing an 1:n relationship:/**	 * The pushNotificationRegistrations	 * @var \Doctrine\Common\Collections\Collection<\My\Project\Domain\Model\Registration>	 * @ORM\OneToMany(mappedBy="User")	 */	protected $registrations;
Is it possible to find all Objects  where the count of the Collection is 0?I tried this in the Repository but it doesn't work:public function countEmpty(){		$query = $this->createQuery();		return $query->matching($query->equals('registrations.count', 0))->count();	}
But this doesn't seem to work.
Do you have an idea how to solve this?
RegardsDavid