How to make query & result cache working for query of associated entity in Symfony2 and Doctrine2?

Question

I'm using memcahe for Symfony Doctrine cache drivers as below:

doctrine:
    orm:
        metadata_cache_driver: memcache
        result_cache_driver: memcache
        query_cache_driver: memcache

I have Article and Tag entities which are manyToMany relationship. I have a controller which fetches all articles (with pagination) and renders them to twig. The below code is in Article repository that uses useQueryCache() and useResultCache() :

$articles = $this->createQueryBuilder('a')
    ->orderBy('a.created_at', 'DESC')
    ->getQuery()
    ->useQueryCache(true)
    ->useResultCache(true)
    ->getResult();

That DQL is perfectly cached for query and result as I did not see the query executed in Symfony Profiler Doctrine section. The problem is the result of the associated entity Tag not being cached. I have the following code in twig:

{% for article in articles %}
    // ...
    {% if article.tags|length %}
        <div class="tag-wrapper clearfix">
            {% for tag in article.tags %}
                // ...
            {% endfor %}
        </div>
    {% endif %}
    // ...
{% endfor %}

The call article.tags seems fetching the tags of the related article all the time without caching. I see all queries are executing on every page load in the Symfony Profiler Doctrine section. Is it possible to cache this?

Answer 1

You're missing a couple of things:

1. you're not joining the tags relation and you're not selecting from it in your query
2. you need to have eager fetching enabled as well for this to work

Take a look here for some pointers: Doctrine2 (Doctrine 2.1) eager loading in Symfony2 .

On another note, I'd be careful doing this if you anticipate a lot of articles with a lot of tags on that one page. Even with caching, you might run into time and/or memory problems down the road.