Symfony 2 - findall() too many DB queries - symfony

Question

why Symfony2 performs 40 DB queries if I use following code:
$em = $this->getDoctrine()->getManager();
$records = $em->getRepository('MyWebBundle:Highlight')->findAll();
I thought that findAll() method returns only all items from Highlight entity and associations to other entities replaces Proxy objects. But now findAll() method gettings all associations entities.
Do you know where is the problem ?
indexAction
public function indexAction() {
$em = $this->getDoctrine()->getManager();
$records = $em->getRepository('MyWebBundle:Highlight')->findAll();
$csrf = $this->get('security.csrf.token_manager');
$token = $csrf->refreshToken(self::FORM_TOKEN_ID);
$params = array(
"data" => array(
"all" => $records,
),
"token" => $token->getValue(),
"static" => array(
"add" => $this->generateUrl("admin_highlight_add"),
"edit" => $this->generateUrl("admin_highlight_edit"),
"del" => $this->generateUrl("admin_highlight_del"),
),
);
$ser = $this->get('jms_serializer');
$jsonContent = $ser->serialize($params, 'json');
return array('jsonContent' => $jsonContent);
}
Highlight entity
namespace My\WebBundle\Entity;
use Doctrine\ORM\Mapping as ORM;
use JMS\Serializer\Annotation as JMS;
/**
* Highlight
*
* #JMS\ExclusionPolicy("none")
* #ORM\Table()
* #ORM\Entity(repositoryClass="My\WebBundle\Entity\HighlightRepository")
*/
class Highlight {
/**
* #var integer
*
* #ORM\Column(name="id", type="integer")
* #ORM\Id
* #ORM\GeneratedValue(strategy="AUTO")
*/
private $id;
/**
* #var string
*
* #ORM\Column(name="abbreviation", type="string", length=8, unique=true)
*/
private $abbreviation;
/**
* #var string
*
* #ORM\Column(name="description", type="string", length=80, nullable=true)
*/
private $description;
/**
* #var string
*
* #ORM\Column(name="color", type="string", length=7)
*/
private $color;
/**
* #var ArrayCollection
* #ORM\OneToMany(targetEntity="Goods", mappedBy="highlight")
*/
private $goods;
/**
* #var ArrayCollection
* #ORM\OneToMany(targetEntity="Calibration", mappedBy="highlight")
*/
private $calibrations;
/**
* Constructor
*/
public function __construct() {
$this->goods = new \Doctrine\Common\Collections\ArrayCollection();
$this->calibrations = new \Doctrine\Common\Collections\ArrayCollection();
}
/**
* Get id
*
* #return integer
*/
public function getId() {
return $this->id;
}
/**
* Set abbreviation
*
* #param string $abbreviation
* #return Highlight
*/
public function setAbbreviation($abbreviation) {
$this->abbreviation = $abbreviation;
return $this;
}
/**
* Get abbreviation
*
* #return string
*/
public function getAbbreviation() {
return $this->abbreviation;
}
/**
* Set description
*
* #param string $description
* #return Highlight
*/
public function setDescription($description) {
$this->description = $description;
return $this;
}
/**
* Get description
*
* #return string
*/
public function getDescription() {
return $this->description;
}
/**
* Set color
*
* #param string $color
* #return Highlight
*/
public function setColor($color) {
$this->color = $color;
return $this;
}
/**
* Get color
*
* #return string
*/
public function getColor() {
return $this->color;
}
/**
* Add goods
*
* #param \My\WebBundle\Entity\Goods $goods
* #return Highlight
*/
public function addGood(\My\WebBundle\Entity\Goods $goods) {
$this->goods[] = $goods;
return $this;
}
/**
* Remove goods
*
* #param \My\WebBundle\Entity\Goods $goods
*/
public function removeGood(\My\WebBundle\Entity\Goods $goods) {
$this->goods->removeElement($goods);
}
/**
* Get goods
*
* #return \Doctrine\Common\Collections\Collection
*/
public function getGoods() {
return $this->goods;
}
/**
* Add calibrations
*
* #param \My\WebBundle\Entity\Calibration $calibrations
* #return Highlight
*/
public function addCalibration(\My\WebBundle\Entity\Calibration $calibrations) {
$this->calibrations[] = $calibrations;
return $this;
}
/**
* Remove calibrations
*
* #param \My\WebBundle\Entity\Calibration $calibrations
*/
public function removeCalibration(\My\WebBundle\Entity\Calibration $calibrations) {
$this->calibrations->removeElement($calibrations);
}
/**
* Get calibrations
*
* #return \Doctrine\Common\Collections\Collection
*/
public function getCalibrations() {
return $this->calibrations;
}
}
Highlight repository is empty

Answer 1

I think the problem comes from the serializer. Since you serializer highliths, each of them has their properties serialized as well which means that lazy query will be performed to retieved Goods which will be also serialized.
You should then prevent this behaviour by adding annotations to highlight's goods property as this
use ...
use JMS\SerializerBundle\Annotation\ExclusionPolicy;
use JMS\SerializerBundle\Annotation\Exclude;
/**
* ...
* #ExclusionPolicy("none")
*/
class Highlight
{
/**
* ...
* #Exclude
*/
private $goods;
}
You can have further details about exclusion stratigies from JMSSerializer doc

Answer 2

findAll itself does not perform many queries. Queries are executed when you access related entity via getters. As relation are not fetched eagerly, they first time are fetched when you are acessing them.
I think serializer access all children to send your object.
See Doctrine documentation
Whenever you have a managed entity instance at hand, you can traverse
and use any associations of that entity that are configured LAZY as if
they were in-memory already. Doctrine will automatically load the
associated objects on demand through the concept of lazy-loading.
To prevent this either disable children serialization or use fetch EAGER or build a DQL query, which prefetch all the children alongside with parents, like (just sample, not valid DQL)
SELECT Highlight, Good, Calibration
FROM Highlights Highlight
LEFT JOIN Highlight.googs Good
LEFT JOIN Goog.calibrations Calibration
WHERE ...