annotate, default aggregation naming and filter annoyance

[dirleyrls]

Going straight to the point, if I do the following:

from django.db import models
...
class Answer(models.Model):
    entry = models.ForeignKey(Question)
...
qsa = Question.objects.annotate(answer_count=models.Count('answer')).filter(answer_count=0)
qsb = Question.objects.annotate(models.Count('answer')).filter(answer__count=0)

qsa will be correctly evaluted, but qsb will raise a "FieldError: Cannot resolve keyword 'count' into field. Choices are ... answer_ _count".

Now, isn't this annoying? The error message is lying!

[dirleyrls]

The patch applies to trunk r14233.

[Russell Keith-Magee]

There's a slight problem here in that filter(answer__count) could be referring to a default aggregate alias, or a field called count on the answer model. However, I think we can live with that ambiguity.

Patch requires tests.

[Ramiro Morales]

In [16252]:

Fixed #14476 -- Fixed resolution of automatically generated annotation names so e.g. filtering based on them works. Thanks dirleyls for the report and patch.

[Tai Lee]

This is still a problem for aggregates.

>>> from django.contrib.auth.models import *
>>> from django.db.models import *
>>> User.objects.annotate(xyz=Count('groups')).aggregate(Max('xyz'))
{'xyz__max': 13}
>>> User.objects.annotate(Count('groups')).aggregate(Max('groups__count'))
Traceback (most recent call last):
  File "<console>", line 1, in <module>
  File "/Users/mrmachine/django/db/models/query.py", line 331, in aggregate
    is_summary=True)
  File "/Users/mrmachine/django/db/models/sql/query.py", line 1000, in add_aggregate
    field_list, opts, self.get_initial_alias(), False)
  File "/Users/mrmachine/django/db/models/sql/query.py", line 1288, in setup_joins
    "Choices are: %s" % (name, ", ".join(names)))
FieldError: Cannot resolve keyword 'count' into field. Choices are: id, name, permissions, user, groups__count

exclude(), filter(), values(), values_list() and order_by() all work, so I assume that aggregate() should as well.

Can we apply the same fix? Let me know if I should open a new ticket instead of re-opening this one.

[Tim Graham]

That test case is fixed by f59fd15c4928caf3dfcbd50f6ab47be409a43b01 (Django 1.8). I will commit the test.

[Tim Graham <timograham@…>]

In 3e1bb5c:

Refs #14476 -- Added a test for default annotation name access in aggregate.

Fixed in f59fd15c4928caf3dfcbd50f6ab47be409a43b01