$batchSize = 100; //Entity Manager will flush every batchSize times
            $i = 0;

            foreach ($aTagCollection as $oTag) {
                $aMapping = $oTag->getMapping();

                foreach ($aMapping as $oMapping) {

                }

                if (($i % $batchSize) === 0) {
                    $this->em->flush(); //Execute all updates every 100 times
                    $this->em->clear(); //Detaches all objects from Doctrine
                }

                $i++;
            }

            $this->em->flush();

/** @ORMOneToMany(targetEntity="Mapping",
        mappedBy="customerLabel", fetch="EXTRA_LAZY",
        cascade={"persist"}, orphanRemoval=true)
    */
    private $mapping;


    public function __construct()
    {
        $this->mapping = new ArrayCollection();
    }


    public function addMapping(Mapping $mapping)
    {
        $this->mapping[] = $mapping;

        return $this;
    }


    public function removeMapping(Mapping $mapping)
    {
        $this->mapping->removeElement($mapping);
    }


    public function getMapping()
    {
        return $this->mapping;
    }

/**
     * @ORMManyToOne(targetEntity="Tag", inversedBy="mapping", cascade={"persist"})
     * @ORMJoinColumn(name="tag_id", referencedColumnName="id", onDelete="CASCADE")
     */
  private $tag;

  public function setTag(Tag $tag = null)
    {
        $this->tag= $tag;

        return $this;
    }

    public function getTag()
    {
        return $this->tag;
    }