[Django] #37402: AttributeError when calling first()/last() on an unordered queryset performing aggregation and grouping by an annotation

[Django]

#37402: AttributeError when calling first()/last() on an unordered queryset
performing aggregation and grouping by an annotation
-------------------------------------+-------------------------------------
Reporter: Jacob | Owner: Django Sprints
Walls |
Type: Bug | Status: assigned
Component: Database | Version: 5.2
layer (models, ORM) |
Severity: Normal | Keywords:
Triage Stage: | Has patch: 0
Unreviewed |
Needs documentation: 0 | Needs tests: 0
Patch needs improvement: 0 | Easy pickings: 0
UI/UX: 0 |
-------------------------------------+-------------------------------------
02eed4f37879b2077496f86bb1378a076b981233 (#36648) assumed all members of a
`GROUP BY` were `Col`s. That introduced an `AttributeError` for cases
involving a function output like `Lower`, shown here:

{{{#!py
from django.db import models
from django.db.models.functions import Lower

class Person(models.Model):
name = models.CharField(max_length=100)

def run():
# Should raise informative TypeError:
# Cannot use QuerySet.first() on an unordered queryset performing
aggregation.
# Add an ordering with order_by().
first = (
Person.objects
.values("name")
.annotate(lower=Lower("name"), count=models.Count("id"))
.first()
)
}}}
{{{#!py
File "/usr/local/lib/python3.12/site-
packages/django/db/models/query.py", line 1187, in first
self._check_ordering_first_last_queryset_aggregation(method="first")
File "/usr/local/lib/python3.12/site-
packages/django/db/models/query.py", line 2330, in
_check_ordering_first_last_queryset_aggregation
{col.target for col in self.query.group_by}
^^^^^^^^^^
AttributeError: 'Ref' object has no attribute 'target'
}}}

It's introduced in 5.2, but we could consider backporting to 6.1 as a
"crashing bug".
--
Ticket URL: <https://code.djangoproject.com/ticket/37402>
Django <https://code.djangoproject.com/>
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[Django]

#37402: AttributeError when calling first()/last() on an unordered queryset
performing aggregation and grouping by an annotation
-------------------------------------+-------------------------------------

Reporter: Jacob Walls | Owner: Django
| Sprints
Type: Bug | Status: assigned
Component: Database layer | Version: 5.2
(models, ORM) |
Severity: Normal | 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 Sarah Boyce):

* stage: Unreviewed => Accepted

--
Ticket URL: <https://code.djangoproject.com/ticket/37402#comment:1>