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
26042	types for GenericForeignKey object_pk?	Brian May	nobody	"Hello,

The documentation suggests that object_id associated with GenericForeignKey should be a PositiveIntegerField. To be precise, the documentation says: ""For most models, this means a PositiveIntegerField."" but doesn't give any more details.

However, this will not work for pk that are not integer. So for the case for django-guardian, where we want be more generic, we use a TextField.

I notice that object_id in django.contrib.admin.models LogEntry is a TextField - although it doesn't use a GenericForeignKey.

The problem with this is when making table joins on Postgresql - postgresql gets upset that the object_id is a string, and a different type on the destination table.

e.g. simplified, we have a db model:

{{{
class UserObjectPermissionBase(models.Model):
    content_type = models.ForeignKey(ContentType)
    object_pk = models.CharField(_('object ID'), max_length=255)
    content_object = GenericForeignKey(fk_field='object_pk')
}}}

We lookup certain objects from this table. For simplicity, lets assume they *all* point to Group  (django.contrib.auth) - i.e. content_type points to the Group content type - as this is where the test case fails. Also we use values, as we only are interested in the object_pk field.

{{{
user_obj_perms_queryset = UserObjectPermissionBase.objects.filter(....).values('object_pk')
}}}

Then we want to lookup all groups that the results of this queryset point to:

{{{
queryset = Group.objects.all()
queryset.filter(Q(pk__in=user_obj_perms_queryset))
}}}

On sqlite and Mysql this works fine. On Postgresql it fails with a Postgresql error:

{{{
======================================================================
ERROR: test_empty_perms_sequence (guardian.testapp.tests.test_shortcuts.GetObjectsForUser)
----------------------------------------------------------------------
Traceback (most recent call last):
  File ""/home/brian/tree/debian/upstream/django-guardian/guardian/testapp/tests/test_shortcuts.py"", line 474, in test_empty_perms_sequence
    set(objects),
  File ""/usr/lib/python2.7/dist-packages/django/db/models/query.py"", line 162, in __iter__
    self._fetch_all()
  File ""/usr/lib/python2.7/dist-packages/django/db/models/query.py"", line 965, in _fetch_all
    self._result_cache = list(self.iterator())
  File ""/usr/lib/python2.7/dist-packages/django/db/models/query.py"", line 238, in iterator
    results = compiler.execute_sql()
  File ""/usr/lib/python2.7/dist-packages/django/db/models/sql/compiler.py"", line 840, in execute_sql
    cursor.execute(sql, params)
  File ""/usr/lib/python2.7/dist-packages/django/db/backends/utils.py"", line 64, in execute
    return self.cursor.execute(sql, params)
  File ""/usr/lib/python2.7/dist-packages/django/db/utils.py"", line 97, in __exit__
    six.reraise(dj_exc_type, dj_exc_value, traceback)
  File ""/usr/lib/python2.7/dist-packages/django/db/backends/utils.py"", line 64, in execute
    return self.cursor.execute(sql, params)
ProgrammingError: operator does not exist: integer = character varying
LINE 1: ...""name"" FROM ""auth_group"" WHERE (""auth_group"".""id"" IN (SELECT...
                                                             ^
HINT:  No operator matches the given name and argument type(s). You might need to add explicit type casts.
}}}

The full SQL of the failing query in this case is:

{{{
SELECT ""auth_group"".""id"", ""auth_group"".""name"" FROM ""auth_group"" WHERE (""auth_group"".""id"" IN (SELECT U0.""object_pk"" FROM ""guardian_userobjectpermission"" U0 INNER JOIN ""auth_permission"" U2 ON ( U0.""permission_id"" = U2.""id"" ) WHERE (U0.""user_id"" = 1 AND U2.""content_type_id"" = 2)) OR ""auth_group"".""id"" IN (SELECT U0.""object_pk"" FROM ""guardian_groupobjectpermission"" U0 INNER JOIN ""auth_group"" U1 ON ( U0.""group_id"" = U1.""id"" ) INNER JOIN ""testapp_customuser_groups"" U2 ON ( U1.""id"" = U2.""group_id"" ) INNER JOIN ""auth_permission"" U4 ON ( U0.""permission_id"" = U4.""id"" ) WHERE (U2.""customuser_id"" = 1 AND U4.""content_type_id"" = 2)))
}}}

Where I believe the problem is that ""auth_group"".""id"" is integer and U0.""object_pk"" is a string, and they can't be compared.

{{{
... WHERE ... ""auth_group"".""id"" IN (SELECT U0.""object_pk"" FROM ...) ...
}}}

So is this a problem with our code? Maybe GenericForeignKey must have an integer value, which excludes it from non-integer pks? Or is this a problem with Django?

Would be interested in feedback.

Thanks"	Bug	closed	contrib.contenttypes	1.9	Normal	duplicate			Unreviewed	0	0	0	0	0	0