Q | Q with nullable related fields generates INNER JOIN where it should be LEFT JOIN

[Simon Percivall]

The following example shows that when ORing Q's Person is LEFT OUTER JOINed and House is erroneously INNER JOINed. At the same time ORing querysets works.

from django.db import models
from django.db.models import Q

class House(models.Model):
    streetname = models.CharField(max_length=255)

class Person(models.Model):
    home = models.ForeignKey(House)

class Rock(models.Model):
    owner = models.ForeignKey(Person, null=True)

# with Q | Q
print Rock.objects.filter(Q(owner__isnull=True) | (Q(owner__home__streetname=''))).query

# with qs | qs
print (Rock.objects.filter(Q(owner__isnull=True)) | Rock.objects.filter(Q(owner__home__streetname=''))).query

This of course means that owner__is_null=True won't work with Q's becaues of the INNER JOIN.

Tested with 1.0.4+, 1.2.3+ and 1.3 trunk@14864

[Tomek Paczkowski]

After countless hours of debugging, one line fix patch is ready. Test included. Done by me & ethlinn (Aleksandra Sendecka).

[Harro]

Tested, works perfect.

[Johannes Dollinger]

cleanup for r16622

[Johannes Dollinger]

I can confirm that this patch also fixes #11052.

[Russell Keith-Magee]

In [16648]:

Fixed #14876 -- Ensure that join promotion works correctly when there are nullable related fields. Thanks to simonpercivall for the report, oinopion and Aleksandra Sendecka for the original patch, and to Malcolm for helping me wrestle the edge cases to the ground.

[Russell Keith-Magee]

In [16671]:

[1.3.X] Fixed #14876 -- Ensure that join promotion works correctly when there are nullable related fields. Thanks to simonpercivall for the report, oinopion and Aleksandra Sendecka for the original patch, and to Malcolm for helping me wrestle the edge cases to the ground.

Backport of r16648 from trunk.