Filtering queryset via ForeignKey to legacy model with OneToOneField as primary doesn't evaluate primary key

[Sam Thompson]

If you have one model with a OneToOneField as primary_key and also specify a db_column and another model with a foreign key to the first, like this:

class UserProfile(models.Model):
    user = models.OneToOneField(User, primary_key=True, db_column='uid')
    email = models.CharField(max_length=255, unique=True)
    username = models.CharField(unique=True, max_length=150)
    class Meta:
        db_table = u'legacy_user'

class OtherModel(models.Model):
    user = models.ForeignKey('my_app.UserProfile', db_column='uid')
    some_data = models.IntegerField()
    another_model = models.ForeignKey('other_app.AnotherModel', db_column='related')
    class Meta:
        db_table = u'legacy_other_model'

When you perform this queryset you get weird SQL:

my_user = UserProfile.objects.get(username='foo')
count = OtherModel.objects.filter(user=my_user).count()
SELECT COUNT(*) FROM `legacy_other_model` WHERE `legacy_other_model`.`uid` = None

But if you explicitly filter on the object's pk, it works:

count = OtherModel.objects.filter(user=my_user.pk).count()
SELECT COUNT(*) FROM `legacy_other_model` WHERE `legacy_other_model`.`uid` = 12345

This doesn't seem to be the expected behavior, looking at: ​http://docs.djangoproject.com/en/dev/topics/db/queries/#queries-over-related-objects

[Carl Meyer]

Using the provided models and queries, I can't replicate this problem in either trunk or 1.2, on SQLite, MySQL, or Postgres. The first query (by my_user) generates the correct SQL for me in every case.

Thanks for the report. Please reopen if you can demonstrate the problem as a patch against Django's own test suite with a failing test case, or in a brand-new simplest-case project running on Django trunk.