Generic Relation query generates incorrect SQL

[Jamie.Norrish@…]

Given the following models:

class Entity (models.Model):
    entity_type = models.CharField(maxlength=30)

class PropertyAssertion (models.Model):
    entity = models.ForeignKey(Entity)
    assertion = models.GenericForeignKey()
    content_type = models.ForeignKey(ContentType, core=True)
    object_id = models.PositiveIntegerField()

class Name (models.Model):
    display_form = models.CharField(maxlength=400, blank=True)
    assertion = models.GenericRelation(PropertyAssertion)

having a method on the Entity class which performs

Name.objects.filter(assertion__entity=self, assertion__content_type=name_content_type)

(where name_content_type is whatever the content_type of the Name model is in the particular database), the generated SQL (slightly abbreviated in terms of the fields selected) is bogus:

SELECT "eats_core_name".*
FROM "eats_core_name" LEFT OUTER JOIN "eats_core_propertyassertion" AS "m2m_eats_core_name__assertion"
  ON "eats_core_name"."id" = "m2m_eats_core_name__assertion"."object_id"
 INNER JOIN "eats_core_propertyassertion" AS "eats_core_name__assertion"
  ON "m2m_eats_core_name__assertion"."object_id" = "eats_core_name__assertion"."id"
WHERE ("m2m_eats_core_name__assertion"."entity_id" = 1 AND "m2m_eats_core_name__assertion"."content_type_id" = 31)

This is joining the propertyassertion table to itself, linked by an identity between object_id and id, which have nothing to do with each other. The results of this query are predictably incorrect.

I don't know what the query was which 0.95 generated, but the code seemed to work then and does not with 0.96.

[fiman]

I believe I am having a problem like this as well, any idea if this can be fixed?

[codefi@…]

generic.py patch

[coderfi@…]

Ok, I poked around the code, and I think I may have fixed it.
Revision: 5818 django/contrib/contenttypes/generic.py
has the following lines:

def m2m_column_name(self):

return self.object_id_field_name

def m2m_reverse_name(self):

return self.object_id_field_name

Does this seem funny to you?
So I poked around the history, and found that the m2m_reverse_name(self) method use to be:

def m2m_reverse_name(self):

return self.model._meta.pk.attname

When I changed the file to that, querying on the 'backwards' generic relationship now seems to work! Awesome!
Not sure if this fixes your problem, but it fixed my problem!

Added generic.py.patch

[Malcolm Tredinnick]

(In [6900]) Fixed #3906 -- Fixed the reverse_m2m_name for a generic relation. Refs #2749.