OutOfMemoryException in PDOConnection using Doctrine iterate result

query.php

<?php
// 7041 rows with content being BLOB content - total table size ~ 2.4 GB
$instructionRepository = $this->getDoctrine()->getRepository('PlusquamContractBundle:Instruction');
$instructionQueryBuilder = $instructionRepository->createQueryBuilder('i')
    ->where('i.content IS NOT NULL')
    ->orderBy('i.id', 'desc');

$instructions = $instructionQueryBuilder->getQuery()->iterate();
?>

I tried to use raw SQL too:

        $sql = "SELECT i.id, i.content FROM instructions AS i";

        $em = $this->getDoctrine()->getManager();
        $stmt = $em->getConnection()->prepare($sql);
        $stmt->execute();

Againg: memory exhausted!

Maybe this helps: http://stackoverflow.com/a/27186091/693546

You made my day @mablae!

Indeed changing the USE_BUFFERED_QUERY attribute on PDO prevents loading anything into memory:

$pdo = $this->getDoctrine()->getManager()->getConnection()->getWrappedConnection();
$pdo->setAttribute(\PDO::MYSQL_ATTR_USE_BUFFERED_QUERY, false);

$sql = "SELECT i.id FROM instructions AS i WHERE i.content IS NOT NULL";

$em = $this->getDoctrine()->getManager();
$stmt = $em->getConnection()->prepare($sql);
$stmt->execute();
$instructionIds = $stmt->fetchAll();

I also tried using the repository too. But it looks like the Manager then does not recognize my attribute change then?

$pdo = $this->getDoctrine()->getManager()->getConnection()->getWrappedConnection();
$pdo->setAttribute(\PDO::MYSQL_ATTR_USE_BUFFERED_QUERY, false);

$instructionQueryBuilder = $instructionRepository->createQueryBuilder('i')
    ->where('i.content IS NOT NULL')
    ->orderBy('i.id', 'desc');

Nice!