How to stop Doctrine 2 from caching a result in Symfony 2?

Question

I want to be able to retrieve the existing version of an entity so I can compare it with the latest version. Eg Editing a file, I want to know if the value has changed since being in the DB.

    $entityManager = $this->get('doctrine')->getEntityManager();
    $postManager = $this->get('synth_knowledge_share.manager');

    $repository = $entityManager->getRepository('KnowledgeShareBundle:Post');
    $post = $repository->findOneById(1); 

    var_dump($post->getTitle()); // This would output "My Title"
    $post->setTitle("Unpersisted new title");

    $existingPost = $repository->findOneById(1); // Retrieve the old entity

    var_dump($existingPost->getTitle()); // This would output "Unpersisted new title" instead of the expected "My Title"

Does anyone know how I can get around this caching?

Answer 1

It's a normal behavior.

Doctrine stores a reference of the retrieved entities in the EntityManager so it can return an entity by it's id without performing another query.

You can do something like :

$entityManager = $this->get('doctrine')->getEntityManager();
$repository = $entityManager->getRepository('KnowledgeShareBundle:Post');
$post = $repository->find(1);

$entityManager->detach($post);

// as the previously loaded post was detached, it loads a new one
$existingPost = $repository->find(1);

But be aware of that as the $post entity was detached, you must use the ->merge() method if you want to persist it again.

Answer 2

You can also use the refresh method, which refreshes the persistent state of an entity from the database, overriding any local changes that have not yet been persisted. Something like:

$entityManager = $this->get('doctrine')->getEntityManager();
$repository = $entityManager->getRepository('KnowledgeShareBundle:Post');
$post = $repository->find(1);

$entityManager->refresh($post);

now $post contains the last version from database.