"pk" alias doesn't work for Meta option "ordering"

[peterd12]

Using the model below:

class MyModel(models.Model):
    part_number = models.CharField(max_length=128)

    class Meta:
        ordering = ['pk']

... yields the error message: "ordering" refers to "pk", a field that doesn't exist

[Malcolm Tredinnick]

From memory, it was fiddly to make this work. I'll have another look at it at some point, but it's not really necessary. Just use "id" instead (or whatever you've named your primary key if there's an explicit key).

[evan_schulz]

Simply skipping validation of 'pk' values (see attached diff) seems like it works with some limited testing, though I'm not sure about all potential implications.

While it is certainly not necessary, it would be nice to be able to use the pk alias consistently.

[Jacob]

It would be nice, but not necessary.

[(none)]

Milestone post-1.0 deleted

[Karen Tracey]

#13297 reported this again and has patches.

[Filip Gruszczyński]

I have added two patches from other ticket with different approaches and a simple test for this bug.

[Julien Phalip]

dgouldin's patch seems like the most promising and the one with the most thorough tests. However, the tests would need to be rewritten using unittests since this is now Django's preferred way.

[Marc Egli]

i basicly picked the patches from evan_schulz and dgouldin, reordered something to not have code before the docstring and wrote a testcase for it.

[Karen Tracey]

Restoring Accepted state; triage state refers to the overall state of the ticket, not the state of the patch.

[Ivan Sagalaev]

Stumbled on this ticket while trying to fix validation errors in admin_views tests. The latest patch applies, fixes the problem and looks correct to me. Marking RFC.

[Luke Plant]

The tests pass without the patch to django/db/models/options.py, haven't investigated why.

It would also be better if the test was put in its own method, for easier testing.

[David Gouldin]

It looks like the resolution of ordering fields now gets run through Query.setup_joins which uses get_field_by_name by resolve the pk alias to the actual primary key field. So, lukeplant, you're correct that the change to options.py is no longer necessary. Now to look at validation.py and see if there's a better general purpose solution than excluding "pk" from going through ordering validation ...

[David Gouldin]

Ok looks like setup_joins includes code to specifically handle the pk case:

​https://github.com/django/django/blob/3904f208b979e55356eefcd0291fb0d7fdfebe45/django/db/models/sql/query.py#L1284

So I feel fine excluding pk specifically from ordering validation in validation.py. I'll update the patch, removing changes to options.py.

[Julien Phalip]

In [17445]:

Fixed #8291 -- Allowed 'pk' to be used as an ordering option in Model.Meta. Thanks to peterd12 for the report and to evan_schulz, gruszczy, frog32 and David Gouldin for their work on the patch.