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
11052	Q-Object disjunction join promotion .. bug	Johannes Dollinger	Malcolm Tredinnick	"(someone who understands why this fails should fix the summary)

Here's a minimal test:
{{{
#!python
from unittest import TestCase
from django.db import models

class A(models.Model):
    name = models.CharField(max_length=30)
    bs = models.ManyToManyField('B')
        
class B(models.Model):
    name = models.CharField(max_length=30)
    c = models.ForeignKey('C')
    
class C(models.Model):
    name = models.CharField(max_length=30)

class ABCTest(TestCase):
    def test(self):
        c = C.objects.create(name='the c')
        b = B.objects.create(c=c, name='the b')
        a_with_b = A.objects.create(name='a with b')
        a_with_b.bs.add(b)
        a_without_b = A.objects.create(name='a without b')
        
        q0 = models.Q(name__contains='without')
        q1 = models.Q(bs__name__contains='foo')
        q2 = models.Q(bs__c__name__contains='foo')
        
        self.assertEqual([a_without_b], list(A.objects.filter(q0)))
        self.assertEqual([a_without_b], list(A.objects.filter(q0 | q1)))
        self.assertEqual([a_without_b], list(A.objects.filter(q0 | q2)))

        # this fails:
        self.assertEqual([a_without_b], list(A.objects.filter(q0 | q1 | q2)))
        
}}}
The offensive query (edited for readabiliy):
{{{
#!sql
SELECT a.id, a.name
FROM a 
  LEFT OUTER JOIN a_bs ON (a.id = a_bs.a_id) 
  LEFT OUTER JOIN b ON (a_bs.b_id = b.id)
  INNER JOIN c ON (b.c_id = c.id) 
WHERE (a.name LIKE %without% OR b.name LIKE %foo% OR c.name LIKE %foo%)
}}}

Obviously this `INNER JOIN` should be a `LEFT OUTER JOIN`.
"	Bug	closed	Database layer (models, ORM)	dev	Normal	duplicate	m2m, join, null, q	Torsten Bronger Dan Watson	Accepted	1	0	1	1	0	0