Filtering by ForeignKey with a legacy model doesn't work without .pk

I have a legacy database that I've set up some models to use. The models look开发者_运维知识库 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 I perform this queryset:

my_user = UserProfile.objects.get(username='foo')
count = OtherModel.objects.filter(user=my_user).count()

I get SQL that looks like:

SELECT COUNT(*) FROM `legacy_other_model` WHERE `legacy_other_model`.`uid` = None

But if I change the count query to this (note the .pk):

count = OtherModel.objects.filter(user=my_user.pk).count()

I get SQL that looks like:

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

Did I set up something wrong in my models?

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Suspect you might need to specify to_field on your OneToOne definition:

user = models.ForeignKey('my_app.UserProfile', db_column='uid', to_field='user')

Does that help?

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At this point, I believe this is a bug in Django.

For future reference, I've reported it here: http://code.djangoproject.com/ticket/15164