I haven't used Rails or ActiveRecord for a long time, but from memory it gives you an escape hatch in the form of Arel that lets you represent parts of your query as SQL while still using the ORM for the rest.

Edit: I think it's something like

    Album
      .select(:id, :name, "SUM(songs.length) AS total_length")
      .left_outer_joins(:songs)
      .group(:id)
      .order("SUM(songs.length) ASC")

I think you don't even need to explicitly wrap it in Arel.

I use rails every day. Looks close enough. You’d just need to specify the fields with the table name, I.e. ‘albums.id’.

Also, for anyone reading, a total_length method dynamically will be added objects returned. :)

I don't know about ActiveRecord or Django specifically, but: the obvious way in their query builder? Adding a joined collection, doing an aggregation on it, and sorting by it, are all easy in any ORM worth bothering with. What did you try and where did you get stuck?

In Django, you would write an annotation as documented at https://docs.djangoproject.com/en/4.1/topics/db/aggregation/...

So something like

  Album.objects.annotate(duration=Sum('track__length')).order_by('duration')

There are also libraries that enable you to define an annotation or aggregation inside a model, that you can then get with a call like select_properties, similar to the built-in select_related (which you use to get a foreign key in one query) and prefetch_related (which is select_related for many-to-many fields).

Thanks. I haven't used Django for ages, but do recall using annotate() in the past. At that time, I didn't need to worry about performance, so didn't look into what happens under the hood, i.e. whether the call generates more than one SQL query.