AssertionError in query.py change_aliases

[Andrew Brown]

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:

class Group(models.Model):
    pass

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

test case:

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
)

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.