id	summary	reporter	owner	description	type	status	component	version	severity	resolution	keywords	cc	stage	has_patch	needs_docs	needs_tests	needs_better_patch	easy	ui_ux
37355	Filtering on a window expression drops duplicated values() columns from the result	Dave Gaeddert		"Filtering against a window function wraps the query (`SQLCompiler.get_qualify_sql()`). If the same column is selected through two lookup paths, the outer query only selects it once, so rows come back one column short:

{{{
class Classification(models.Model):
    pass

class Employee(models.Model):
    name = models.CharField(max_length=40)
    department = models.CharField(max_length=40)
    salary = models.PositiveIntegerField()
    classification = models.ForeignKey(Classification, models.CASCADE, null=True)

Employee.objects.annotate(
    rank=Window(Rank(), partition_by=""department"", order_by=""-salary"")
).filter(rank=1).values_list(""classification_id"", ""classification__id"", ""name"")
# [(1, 'Adams'), (1, 'Wilkinson'), ...]
# expected [(1, 1, 'Adams'), (1, 1, 'Wilkinson'), ...]
}}}

Asked for three fields, got 2-tuples, no exception. Adding `.order_by(""department"")` turns it into `ORDER BY position 3 is not in select list` on PostgreSQL.

Reproduces on 5.2, 6.0, and main, on PostgreSQL 16 and SQLite.

Cause: `get_qualify_sql()` collects the aliases to keep in the outer query in a dict keyed by expression (`{expr: alias for expr, _, alias in self.get_select(with_col_aliases=True)[0]}`), so two selections of an equal expression collapse into one entry. This is the duplicate-''expression'' half of #36288, which fixed the duplicate-''field name'' case (`values_list(""x"", ""x"")`) from the same regressing commit.

Found while verifying the fix for #37222. Jacob Walls agreed this is a bug on the PR thread: https://github.com/django/django/pull/21659#discussion_r3899304732

Fix with a regression test on my fork: https://github.com/davegaeddert/django/pull/5 — happy to open it against main if accepted.

(AI assistance: Claude Code was used to find and reproduce this and draft the fix; I verified the reproducer and test results.)"	Bug	new	Database layer (models, ORM)	5.2	Normal		window expressions		Unreviewed	0	0	0	0	0	0