Inherited model doesn't correctly order by "-pk" when specified on Parent.Meta.ordering

[Jon Dufresne]

Given the following model definition:

from django.db import models

class Parent(models.Model):
    class Meta:
        ordering = ["-pk"]

class Child(Parent):
    pass

Querying the Child class results in the following:

>>> print(Child.objects.all().query)
SELECT "myapp_parent"."id", "myapp_child"."parent_ptr_id" FROM "myapp_child" INNER JOIN "myapp_parent" ON ("myapp_child"."parent_ptr_id" = "myapp_parent"."id") ORDER BY "myapp_parent"."id" ASC

The query is ordered ASC but I expect the order to be DESC.

[Simon Charette]

Interesting ordering is effectively one of the rare Meta ​attribute preserved during MTI inheritance.

I also wonder if ordering = ('pk',) should be special cased to order by the local child class primary key which would be "myapp_child"."parent_ptr_id" in this case since it should result in the same resulset because of foreign key integrity and avoid an unnecessary JOIN in the cases where no parent fields are involved.

[Jon Dufresne]

​https://github.com/django/django/pull/12470

I also wonder if ordering = ('pk',) should be special cased to order by the local child class primary key which would be "myapp_child"."parent_ptr_id" in this case since it should result in the same resulset because of foreign key integrity and avoid an unnecessary JOIN in the cases where no parent fields are involved.

Interesting enough, ordering by ["-id"] was already doing that. So I agree that "-pk" should behave the same.

[Simon Charette]

I would expect Parent.meta.ordering = ["id"] to result in ORDER BY "myapp_parent"."id" while Parent.meta.ordering = ["pk"] results in ORDER BY "myapp_child"."parent_ptr_id".

Isn't that the case right now?

[Abhijeet Viswa]

I'm changing the owner and status since there already is a patch by the reporter.

[Mariusz Felisiak <felisiak.mariusz@…>]

In 013147fa:

Fixed #31285 -- Fixed inherited Meta.ordering of "-pk".