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
37474	Combined queries with values() ordered by a non-selected field crash with IndexError after a clone is	cheek-walnut		"On a combined query (e.g. `union()`) using `values()` and ordered by a field that isn't in `values()`, evaluating one queryset breaks other querysets cloned from the same query.

{{{#!python
class Author(models.Model):
    name = models.CharField(max_length=20)
    age = models.IntegerField()

class Book(models.Model):
    title = models.CharField(max_length=20)
    pages = models.IntegerField()
    author = models.ForeignKey(Author, models.CASCADE, related_name=""books"")
}}}

With two books (pages 10 and 20):

{{{#!python
qs = Book.objects.filter(pages__gt=0).union(Book.objects.filter(pages__gt=0))
qs = qs.values(""title"").order_by(""pages"")
qs2 = qs.all()
list(qs)   # [{'title': 'b1'}, {'title': 'b2'}]
list(qs2)  # IndexError
}}}

{{{
  File ""django/db/models/sql/compiler.py"", line 77, in setup_query
    self.select, self.klass_info, self.annotation_col_map = self.get_select(
  File ""django/db/models/sql/compiler.py"", line 295, in get_select
    expression = cols[expression]
IndexError: tuple index out of range
}}}

Evaluating `qs2` first breaks `qs` instead. `list(qs[:1])` followed by `list(qs)`, or evaluating `qs.all()` twice, crash the same way. Ordering by a selected field (`order_by(""title"")`) works.

Expected: both evaluations return `[{'title': 'b1'}, {'title': 'b2'}]`, as on Django 5.1.

Regression in 65ad4ade74dc9208b9d686a451cd6045df0c9c3a (Refs #28900): the queries work on its parent and fail on it. Reproduced on 5.2.20, 6.0.11, 6.1.4 and main (5bd95c57a2) with SQLite; 5.1.16 is not affected.

The cause appears to be that `Query.clone()` (django/db/models/sql/query.py:387-395) doesn't copy the `selected` dict, so clones share it, while `Query.add_select_col()` (:2265, called from `SQLCompiler.get_order_by()` at compiler.py:544 for combined queries) mutates it in place and each clone keeps its own `select` tuple. This is different from #37466, which is about composite primary keys.

AI disclosure: found during a code audit with Claude Code 2.1.317 (Claude Opus 5.5), which also reduced the test case and ran it on the versions above and on 65ad4ade74 and its parent. I reviewed this report and re-ran the reproduction on main and 5.1.16."	Bug	new	Database layer (models, ORM)	6.1	Low				Unreviewed	0	0	0	0	0	0