Extra order by ignores descending orderings

[Bertrand Bordage]

Consider this simple model:

class Test(Model):
    name = CharField(max_length=50)
    class Meta(object):
        db_table = 'test'

Test.objects.extra(order_by=['-name']) should be converted to something like SELECT * FROM test ORDER BY name DESC, but instead it becomes SELECT * FROM test ORDER BY name ASC. The minus is ignored.

It wasn’t happening in Django 1.6 and 1.7.

(This issue was discovered in ​the test suite of django-cachalot)

[Josh Smeaton]

Based on looking at the models of the linked test suite I'm guessing that this is hitting the "duplicate" order by clause. It's keeping the default ordering of the model, which is by name ascending, and removing the extra which is by name descending. Extra ordering should prevent the default ordering from being applied, and the negative sign should be preserved.

[Bertrand Bordage]

I tested without default ordering, the issue is still there.

But I wasn’t precise enough in my report, it’s only happening when we specify the table name:

>>> print Test.objects.all().query
SELECT […] FROM "test"
>>> print Test.objects.extra(order_by=['-name']).query
SELECT […] FROM "test" ORDER BY "test"."name" DESC
>>> print Test.objects.extra(order_by=['-test.name']).query
SELECT […] FROM "test" ORDER BY ("test".name) ASC
>>> print Test.objects.extra(order_by=['-"test"."name"']).query
SELECT […] FROM "test" ORDER BY ("test"."name") ASC

[Josh Smeaton]

Thanks for the follow up. That makes it even easier to track down.

​https://github.com/django/django/blob/6e13c0490d67cdf210411f08feca3b78a49645ea/django/db/models/sql/compiler.py#L259

This is the block responsible, and should be fairly trivial to fix.

[Josh Smeaton]

​https://github.com/django/django/pull/3947

[Josh Smeaton <josh.smeaton@…>]

In 69c6a6868f0b4137bb293ff4326ecf4681506c37:

Fixed #24174 -- Fixed extra order by descending

[Josh Smeaton <josh.smeaton@…>]

In 0c910823c166b827b090df5c5c8be9e502a14d8c:

[1.8.x] Fixed #24174 -- Fixed extra order by descending

Backport of 69c6a6868f0b4137bb293ff4326ecf4681506c37 from master