Doctrine 2 bulk insert/update memory

Question

Consider this code (wrapped inside a function):

    $manager = $this->manager; // local ref
    $q = $manager->createQuery('select c from VendorFeedBundle:Category c');
    $iterableResult = $q->iterate();
    $i = 0;
    $batchSize = 500;

    foreach($iterableResult as $row) {
        $category = $row[0];

        $struct = explode(' ' . $this->separator . ' ', $category->getPath());
        unset($struct[count($struct) - 1]);
        $path = implode(' ' . $this->separator . ' ', $struct);

        if (!$parent = $this->repo->findOneBy(['path' => $path])) {
            continue;
        }

        $category->setParent($parent);

        // flush every x entities
        if (($i % $batchSize) == 0) {
            echo 'Flushing batch...' . "\n";
            echo 'Memory: ' . $this->getReadableSize(memory_get_usage()) . "\n";

            $manager->flush();
            $manager->clear();

            echo 'After batch...' . "\n";
            echo 'Memory: ' . $this->getReadableSize(memory_get_usage()) . "\n";
        }
        ++$i;
    }

    // flush the remaining
    $manager->flush();
    $manager->clear();

It logs the following in my terminal:

Creating tree...
Memory: 14.91 MB
Flushing batch...
Memory: 18.46 MB
After batch...
Memory: 18.79 MB
Flushing batch...
Memory: 21.01 MB
After batch...
Memory: 23.29 MB
Flushing batch...
Memory: 25.36 MB
After batch...
Memory: 27.87 MB
Flushing batch...
Memory: 29.88 MB
.... etc

The getReadAbleSize method is not leaking any variables to a global scope or anything. I've read and followed advice about doctrine2 bulk inserts/updates (batch processing): http://docs.doctrine-project.org/en/latest/reference/batch-processing.html

What am I doing wrong? 3~4 MB memory increase per 500 items seems like a (little) leak to me.

Sidenote: I need to update the items this way because my system is split up in 2 processes; first I insert the categories and secondly I update the parent relationship.

My category class is a basic Doctrin2 entity with a few Gedmo extensions added to it (tree, translateable, timestampable) See: http://pastie.org/private/oiiyf54zjuouhiqjsjislg

My complete script (which is iterating and updating categories): http://pastie.org/private/k5x240vr4taepczhqa4tva

Answer 1

1. Set SQL logger to null

$em->getConnection()->getConfiguration()->setSQLLogger(null);

2. Manually call function gc_collect_cycles() after $em->clear()

$em->clear(); gc_collect_cycles();

Don't forget to set zend.enable_gc to 1, or manually call gc_enable() before use gc_collect_cycles()

3. Add --no-debug option if you run command from console.