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
26959	AssertionError in query.py change_aliases	Andrew Brown	nobody	"I'm running into this AssertionError on a fairly complex query in my app, involving ORing two querysets together.

I've tried on both Django 1.9.8 and 1.10rc1

Here's the backtrace:
{{{
Traceback (most recent call last):
  File ""/.../app/tests.py"", line 32, in test_asserterror
    return qs1 | qs2
  File ""/.../env/local/lib/python2.7/site-packages/django/db/models/query.py"", line 318, in __or__
    combined.query.combine(other.query, sql.OR)
  File ""/.../env/local/lib/python2.7/site-packages/django/db/models/sql/query.py"", line 573, in combine
    w.relabel_aliases(change_map)
  File ""/.../env/local/lib/python2.7/site-packages/django/db/models/sql/where.py"", line 129, in relabel_aliases
    child.relabel_aliases(change_map)
  File ""/.../env/local/lib/python2.7/site-packages/django/db/models/sql/where.py"", line 131, in relabel_aliases
    self.children[pos] = child.relabeled_clone(change_map)
  File ""/.../env/local/lib/python2.7/site-packages/django/db/models/lookups.py"", line 103, in relabeled_clone
    new.rhs = new.rhs.relabeled_clone(relabels)
  File ""/.../env/local/lib/python2.7/site-packages/django/db/models/sql/query.py"", line 346, in relabeled_clone
    clone.change_aliases(change_map)
  File ""/.../env/local/lib/python2.7/site-packages/django/db/models/sql/query.py"", line 793, in change_aliases
    assert set(change_map.keys()).intersection(set(change_map.values())) == set()
AssertionError
}}}

And I've managed to simplify down a test case the best I could.

models.py:

{{{#!python
class Group(models.Model):
    pass

class User(models.Model):
    groups = models.ManyToManyField(Group, related_name=""members_of"")
    friends = models.ManyToManyField('self')
}}}

test case:
{{{#!python
g1 = models.Group.objects.create()
g2 = models.Group.objects.create()
g3 = models.Group.objects.create()

u1 = models.User.objects.create()

otherusers = models.User.objects.exclude(
    pk=u1.pk
).exclude(
    friends=u1
)

qs1 = otherusers.filter(
    groups=g1
).filter(
    groups=g2
)

qs2 = otherusers.filter(
    groups=g1
).filter(
    groups=g3
)

list(qs1 | qs2)
}}}

Let me know if I can provide any other information that would  be helpful. Oddly enough in my app it only happens part of the time, seemingly at random, but this test case seems to hit the assertion every time for me."	Bug	closed	Database layer (models, ORM)	1.9	Normal	duplicate			Unreviewed	0	0	0	0	0	0