[Django] #36292: Group By Aggregations are Breaking in 5.2

[Django]

#36292: Group By Aggregations are Breaking in 5.2
-------------------------------------+-------------------------------------
Reporter: Patrick Altman | Type: Bug
Status: new | Component: Database
| layer (models, ORM)
Version: 5.2 | Severity: Normal
Keywords: | Triage Stage:
| Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------
When I upgraded to 5.2 today, a number of my query sets broke tracebacks
on building the query. I didn't notice anything in the BIC of the release
notes.

I tossed together a project to make it easier to clone and repro:
https://github.com/paltman/groupby-demo-dj52

But in summary, when I have some models like:

{{{
from django.db import models


class Bag(models.Model):
kind = models.PositiveBigIntegerField(unique=True)


class Order(models.Model):
blended_at = models.DateTimeField(null=True, default=None)
gross_weight = models.FloatField(null=True, default=None)
tare_weight = models.FloatField(null=True, default=None)
total_tons = models.FloatField(null=True, default=None)
blend_status = models.CharField(max_length=2, blank=True)
bag_type = models.ForeignKey(Bag, on_delete=models.CASCADE, null=True)
}}}

and try to build a queryset like:

{{{
from django.db.models import Case, When, F, FloatField, Value, Sum

from .models import Order


TONS_ANNOTATION = dict(
blended_tons=Case(
When(
gross_weight__gt=0,
then=(F("gross_weight") - F("tare_weight")) / Value(2000)
),
default=F("total_tons"),
output_field=FloatField()
)
)

dry_tons = Order.objects.filter(
blended_at__date__range=["2025-03-01", "2025-03-31"],
).annotate(
**TONS_ANNOTATION
).values(
"blend_status",
"blended_at__date",
"bag_type__kind",
).annotate(
tons=Sum("blended_tons")
)
}}}

I get the following traceback when trying to just print the query out:

{{{
>>> print(dry_tons.query)
Traceback (most recent call last):
File "<console>", line 1, in <module>
File "/usr/local/lib/python3.13/site-
packages/django/db/models/sql/query.py", line 342, in __str__
sql, params = self.sql_with_params()
~~~~~~~~~~~~~~~~~~~~^^
File "/usr/local/lib/python3.13/site-
packages/django/db/models/sql/query.py", line 350, in sql_with_params
return self.get_compiler(DEFAULT_DB_ALIAS).as_sql()
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^
File "/usr/local/lib/python3.13/site-
packages/django/db/models/sql/compiler.py", line 765, in as_sql
extra_select, order_by, group_by = self.pre_sql_setup(
~~~~~~~~~~~~~~~~~~^
with_col_aliases=with_col_aliases or bool(combinator),
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
)
^
File "/usr/local/lib/python3.13/site-
packages/django/db/models/sql/compiler.py", line 85, in pre_sql_setup
self.setup_query(with_col_aliases=with_col_aliases)
~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/usr/local/lib/python3.13/site-
packages/django/db/models/sql/compiler.py", line 74, in setup_query
self.select, self.klass_info, self.annotation_col_map =
self.get_select(
~~~~~~~~~~~~~~~^
with_col_aliases=with_col_aliases,
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
)
^
File "/usr/local/lib/python3.13/site-
packages/django/db/models/sql/compiler.py", line 286, in get_select
expression = cols[expression]
~~~~^^^^^^^^^^^^
IndexError: tuple index out of range
}}}

Posted here earlier: https://forum.djangoproject.com/t/my-group-by-
aggregations-are-breaking-in-5-2/40162/1 but after I posted I realized
this seems like a bug just in the fact that it's been working for a while
now in previous versions.
--
Ticket URL: <https://code.djangoproject.com/ticket/36292>
Django <https://code.djangoproject.com/>
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[Django]

#36292: Group By Aggregations are Breaking in 5.2
-------------------------------------+-------------------------------------

Reporter: Patrick Altman | Owner: Simon
| Charette
Type: Bug | Status: assigned
Component: Database layer | Version: 5.2
(models, ORM) |
Severity: Release blocker | Resolution:
Keywords: | Triage Stage: Accepted

Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------

Changes (by Simon Charette):

* owner: (none) => Simon Charette
* severity: Normal => Release blocker
* stage: Unreviewed => Accepted
* status: new => assigned

Comment:

I haven't figured out a solution yet but this is a regression due to
#28900 (65ad4ade74dc9208b9d686a451cd6045df0c9c3a).
--
Ticket URL: <https://code.djangoproject.com/ticket/36292#comment:1>