Question

This is a hypothetical for simplicity. In my Django app I have models for Kit, KitSku, and Sku. The KitSku model associates a Sku with a Kit and also provides the quantity of that Sku in that kit. In the template I have something like:

<!-- SELECT * FROM kitsku_table WHERE kit_id = <Kit.id> -->
{% for kitsku in kit.kitsku_set.all %}
  <!-- SELECT * FROM sku_table WHERE sku = <KitSku.sku> -->
  <div>{{ kitsku.sku.name }}</div>
{% endfor %}

Now, the problem here is that Django is querying all of the KitSku rows and then it queries each sku within that for loop in a separate SQL query for each iteration.

Can I make the SQL query resulting from the kitsku_set.all() call perform a JOIN with the Sku model?

That first query needs to be more like:

SELECT * FROM kitsku_table k LEFT JOIN sku_table s ON (k.sku = s.sku) 
WHERE k.kit_id = <Kit.id>

Answer 1

Do this type of logic in the view, and use select_related() to directly query the foreign keys

kitskus = Kit.objects.get(id=3).kitsku_set.select_related('sku')
return direct_to_template(request, "mytemplate.html", {'kitskus': kitskus})