ModelFormSet may query wrong database backend

[Pierre Chifflier]

When using a ModelFormSet with a queryset using a DB different from the 'default' one, the validation of the fields fails.

debugging the code shows that the db used is the wrong one:

-> self.instance.clean_fields(exclude=exclude)
  /usr/lib/pymodules/python2.5/django/db/models/base.py(902)clean_fields()
-> setattr(self, f.attname, f.clean(raw_value, self))
  /usr/lib/pymodules/python2.5/django/db/models/fields/__init__.py(194)clean()
-> self.validate(value, model_instance)
  /usr/lib/pymodules/python2.5/django/db/models/fields/related.py(831)validate()
-> qs = self.rel.to._default_manager.filter(**{self.rel.field_name:value})
> /usr/lib/pymodules/python2.5/django/db/models/manager.py(141)filter()
-> return self.get_query_set().filter(*args, **kwargs)
(Pdb) p self.get_query_set().db
'default'

The ModelFormSet was created by creating Form with a queryset:

def make_projecttask_formset(p, extra=0):
    class _ProjectTaskForm(forms.ModelForm):
        project = forms.ModelChoiceField(label="Project",
                queryset=Project.objects.using('otherdb').filter(project_id=p.project_id))
...
    return modelformset_factory(ew_projecttask, form=_ProjectTaskForm, extra=extra)

Expected behavior: used db should be the same as in the queryset

Note: it seems the problems is known (bug not fixed):

• discussed in ​http://groups.google.com/group/django-developers/browse_thread/thread/22e52a2fd03eac82
• someone proposed a patch at ​http://github.com/aparo/django/commit/edcdc1d9364224fcbc3b810b9d9fa19a10cd537c (only the fields/related part imho)

[patchhammer]

13677.diff fails to apply cleanly on to trunk

[Jacob]

Milestone 1.3 deleted

[Aymeric Augustin]

Change UI/UX from NULL to False.

[Tobias Kunze]

I tried to build a ModelFormSet that uses the alternative database, and as long as you specify for related objects to use the alternative database, too, the validation is successful. (If you forget to specify the second database, it throws a very explicit error stating that this model relation is not possible).

My test case is avaliable here: ​https://github.com/rixx/django_ticket13667 - please provide a failing example if you want to reopen this ticket.

[Tim Graham]

Just to be sure, could you clarify what the mistake is in the test in the patch attached to the ticket (13677.diff​)?

[Tobias Kunze]

I'm sorry: I made a mistake in reproducing the issue and porting the patch to current Django. After porting the patch I can confirm that the regression test is valid. I'm not quite sure the implementation is what we want, but I'll push it and we can discuss the PR.

[Tim Graham]

I left some comments for improvement on the PR.