Does calling a method from template query the database each time?

Question

Say you have the following method in a model:

    def get_images(self):
        return ReleaseImage.objects.filter(release=self.id)

And you call it from a template like so:

{% if release.get_images %}{{ MEDIA_URL }}{{ release.get_images.first }}{% endif %}

Does the database get queried twice, or is there some behind-the-scenes optimization that prevents this? It might be highly inefficient if not.

willeM_ Van Onsem · Accepted Answer · 2025-02-01 08:48:59Z

1

It queries twice here, yes. But we can optimize it with a {% with … %} template tag ^[Django-doc]:

{% with images=release.get_images %}
{% if images %}{{ MEDIA_URL }}{{ images.0 }}{% endif %}
{% endwith %}

As with (most) Django template tags, you can not add spaces around the equal sign (=).

edited Feb 1 at 8:48

answered Jan 31 at 21:14

willeM_ Van Onsem

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2 Comments

bur Jan 31 at 21:49

It's useful to add that the with tag does not accept spaces around the = , I struggled with that for a fair few minutes before I realized haha.

willeM_ Van Onsem Feb 1 at 8:48

@bur: yes, although I think that is the case for (most) template tags. The Django template engine has some peculiarities regarding syntax. I actually don't really understand why they keep maintaining it, and just don't switch to Jinja, which is very similar.

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