Doctrine cascade persistence never check if object exists Symfony 2 - symfony

Question

I have a form which save queries. This is organized in the way of a people who ask is saved also this create a threat where is saving the id_question and emailperson. The issue is that the same person does another question. Logically, this report a primary key error:
SQLSTATE[23000]: Integrity constraint violation: 1062 Duplicate entry 'drj00003#ujaen.es' for key 'PRIMARY'
How do I fix it? In the constructor of class I cannot check if this exists and all registers are generated automatically in cascade without form.
It should be easy but I can't solve this.
class HiloType extends AbstractType{
/**
* #param FormBuilderInterface $builder
* #param array $options
*/
public function buildForm(FormBuilderInterface $builder, array $options)
{
$builder
->add('consultanteemail', new ConsultanteType(), array ('label' => false))
->add('personalemail', 'entity', array(
'label' => 'Personal de Soporte',
'class' => 'GuiasDocentes\AppBundle\Entity\Personal',
'property' => 'Enunciado',
'by_reference' => 'false',
'query_builder' => function(PersonalRepository $pr) {
$query= $pr->createQueryBuilder('u')
;
return $query;
},
'empty_value' => 'Elige un perfil de consulta:',
))
;
}
...
class Hilo{
/**
* #var integer
*
* #ORM\Column(name="id", type="integer", nullable=false)
* #ORM\Id
* #ORM\GeneratedValue(strategy="IDENTITY")
*/
private $id;
/**
* #var \GuiasDocentes\AppBundle\Entity\Personal
*
* #ORM\ManyToOne(targetEntity="Personal", inversedBy="hilos", cascade ={"ALL"})
* #ORM\JoinColumns({
* #ORM\JoinColumn(name="personalEmail", referencedColumnName="email")
* })
*/
private $personalemail;
/**
* #var \GuiasDocentes\AppBundle\Entity\Consultante
*
* #ORM\ManyToOne(targetEntity="Consultante", inversedBy="hilos", cascade ={"ALL"} )
* #ORM\JoinColumns({
* #ORM\JoinColumn(name="consultanteEmail", referencedColumnName="email")
* })
*/
private $consultanteemail;
/* Customized code */
/**
* #ORM\OneToMany(targetEntity="GuiasDocentes\AppBundle\Entity\Consulta", mappedBy="hiloid")
* #Assert\Valid()
*/
private $consultas;
public function __construct(){
$this->consultas = new ArrayCollection();
}
public function setConsultas (Consulta $consulta){
$this->hilos[]=$consulta;
}
public function addConsulta (\GuiasDocentes\AppBundle\Entity\Consulta $consulta){
$this->hilos[] = $consulta;
}
/* End customized code */
...
class Consultante{
/**
* #var string
*
* #ORM\Column(name="email", type="string", length=50, nullable=false)
* #ORM\Id
*/
private $email;
/**
* #var string
*
* #ORM\Column(name="nombre", type="string", length=30, nullable=true)
*/
private $nombre;
/**
* #var string
*
* #ORM\Column(name="apellidos", type="string", length=50, nullable=true)
*/
private $apellidos;
/* Customized code */
/**
* #ORM\OneToMany(targetEntity="GuiasDocentes\AppBundle\Entity\Hilo", mappedBy="consultanteemail")
* #Assert\Valid()
*/
private $hilos;
public function __construct(){
$this->hilos = new ArrayCollection();
}
public function setHilos (Hilo $hilo){
$this->hilos[]=$hilo;
}
public function addHilo (\GuiasDocentes\AppBundle\Entity\Hilo $hilo){
$this->hilos[] = $hilo;
}
public function setEmail($email)
{
$this->email = $email;
return $this;
}
/* End customize code */
...
public function contactoAction (Request $request){
$session = $request->getSession();
$perfil = $session->get('perfil');
$consultaHasAsignatura = new ConsultaHasAsignatura();
$form = $this->createForm(new ConsultaHasAsignaturaType(), $consultaHasAsignatura);
if ($request->isMethod('POST')){
$form->handleRequest($request);
if($form->isValid()){
$em = $this->getDoctrine()->getManager();
$em->persist($consultaHasAsignatura);
$em->flush();
return $this->redirectToRoute('guias_docentes_app_homepage');
}
}
return $this->render('GuiasDocentesAppBundle:FAQ:contacto.html.twig', array('perfil'=>$perfil,
'form' => $form->createView()
));
}