Aggregate or Annotaion on previously Annotated values

[eye-see-you@…]

from django.db.models import Count, Sum, F

myModel.objects \
               .annotate(a_count=Count('field_a'), b_count=Count('field_b')) \
               .annotate(total=F('a_count')+F('b_count')) \
               .order_by('total')

This query is going to raise AttributeError: 'ExpressionNode' object has no attribute 'split'

I don't find any method in django ORM to support such kind of operations (in which two fields are involved).

[anonymous]

Instead of using .extra

myModel.objects.extra(select={'total': 'Count(field_a)+Count(field_b)'})

The method which I don't want to use because its not cool(violation of ORM concept).

[Aymeric Augustin]

The ORM isn't intended to be a complete abstraction to SQL; it's just a shortcut for the most common queries. Dropping to raw SQL (or .extra if you really need to) isn't a violation of the ORM concept; it's part of the ORM concept — at least, as understood in Django.

The docs talk about ​aggregating annotations, but not about re-annotating annotations. I'm not sure it's possible to support it while keeping the code complexity under control.

[Aymeric Augustin]

If someone has a good patch for this, why not, but at the moment there isn't one.