Deleting search objects related many-to-one to a given posting

gistfile1.txt

// In my Search entity class:

    /**
     * @ORM\ManyToOne(targetEntity="Posting", inversedBy="words")
     * @ORM\JoinColumn(name="posting_id", referencedColumnName="id", onDelete="cascade")
     */
    protected $posting;

// Later, when I want to delete the Search objects for a given Posting entity:

        foreach ($entity->getWords() as $search)
        {
            $em->persist($search);
            $em->remove($search);
        }

// This produces:

  A new entity was found through the relationship 'Duke\DukeListBundle\Entity\Posting#words' that was not configured to cascade persist operations for entity: Duke\DukeListBundle\Entity\Search@000000003fbc63ae000000000717a61e. Explicitly persist the new entity or configure cascading persist operations on the relationship. If you cannot find out which entity causes the problem implement 'Duke\DukeListBundle\Entity\Search#__toString()' to get a clue.