Doctrine query builder offset changeable - php

Question

I'm a Symfony beginner & I'm trying to load my contact from the database using the Doctrine Query Builder as follows:
ContactRepository.php:
public function getcontactByLimit($offset, $limit)
{
$queryBuilder = $this->_em->createQueryBuilder()
->select('contact')
->from($this->_entityName, 'contact')
->setFirstResult( $offset )
->setMaxResults( $limit )
$query = $queryBuilder->getQuery();
$results = $query->getResult();
return $results;
}
DefaultController.php:
$contacts = $repository->getContactByLimit(0, 3);
Now I want to get all contacts I have in the database but just 3 by 3, what means I'm supposed to change the offset value at every loop (to 3 then 6 then 9...)
Have you any idea how to do it ?

Answer 1

It seems for me, that you want to load objects in parts to save memory.
For that, you can use an Iterator:
$query = $queryBuilder->getQuery();
$iterator = $query->iterate();
return $iterator;
And iterate in your Controller
foreach ($iterator as $row) {
}
What will happen, is that doctrine uses PDO and select your result but not read it out directly. There is a cursor on the ResultSet of the Database, which is moving on each iteration. So your PHP-Application will get each Row from Database one by one.
To get 3 by 3 packages, you could use the internal position:
$currentPackage = array();
foreach ($iterator as $position => $row) {
if($position % 3){
// do here something with your 3er package before unset
$currentPackage = array();
$entityManager->clear(); // clear doctrine, could free memory
}
$currentPackage[] = $row;
}

Answer 2

That what I did, & it works fine !
DefaultController.php:
$offset = 0;
$limit = 2;
$sizeData /= $limit;
for( $i = 0; $i < $sizeData; $i++)
{
$contacts = $repository->getListByLimit($offset, $limit);
$sender->setContacts($contacts);
$offset += $limit;
}
ContactRepository.php:
public function getListByLimit($offset, $limit)
{
$queryBuilder = $this->_em->createQueryBuilder()
->select('contact')
->from($this->_entityName, 'contact')
->setFirstResult( $offset )
->setMaxResults( $limit );
$query = $queryBuilder->getQuery();
$results = $query->getResult();
return $results;