nulls_distinct not honored for ALTER

[Peter Thomassen]

The SQL template for creating uniqueness constraints (BaseDatabaseSchemaEditor.sql_create_unique) does not include the nulls_distinct field necessary to support #34701.

As a result, adding a UNIQUE NULLS NOT DISTINCT on migration will end up with standard UNIQUE constraint.

Replacing

        "UNIQUE (%(columns)s)%(deferrable)s"

with

        "UNIQUE%(nulls_distinct)s (%(columns)s)%(deferrable)s"

on line 114 (5.0rc1) worked for me. I'll be happy to create a PR for that.

Also, I noticed that the include field does not appear to be rendered in this template as well, although the UniqueConstraint class does have an include argument. I wonder if it should also be included there, as follows (inspired by the sql_create_unique_index template, which I think should only differ w.r.t. to the condition field):

        "UNIQUE%(nulls_distinct)s (%(columns)s)%(include)s%(deferrable)s"

I picked "release blocker" because it's a new feature that's broken, not a random bug unrelated to this release. I hope that was right.

[Simon Charette]

Definitely a release blocker thanks for testing against the release candidate.

Please submit a PR with the proposed changes and a regression test. I'd suggest making the includes change in a distinct commit as this feature was added in 3.2 and thus I don't think it will qualify for a backport.

[Mariusz Felisiak]

Peter, Do you have time today or tomorrow to work on this? The final 5.0 release is scheduled for Monday, so we're in a hurry. If you don't have time, I can handle it.

[Peter Thomassen]

I should be able to do it tomorrow.

[Peter Thomassen]

I should be able to do it tomorrow.

[Peter Thomassen]

FYI, I am on it. -- I found that the includes field missing in this template isn't a bug, because when that modifier is given, another template is used (sql_create_unique_index). The patch will thus contain only the fix for sql_create_unique.

[Peter Thomassen]

Patch is here: ​https://github.com/django/django/pull/17567

Note the comment there regarding the second test.

[Mariusz Felisiak <felisiak.mariusz@…>]

In 54cb1a7e:

Fixed #35002 -- Made UniqueConstraints with fields respect nulls_distinct.

Regression in 595a2abb58e04caa4d55fb2589bb80fb2a8fdfa1.

[Mariusz Felisiak <felisiak.mariusz@…>]

In cb013fc:

[5.0.x] Fixed #35002 -- Made UniqueConstraints with fields respect nulls_distinct.

Regression in 595a2abb58e04caa4d55fb2589bb80fb2a8fdfa1.

Backport of 54cb1a7e160089cea438f50fdb70aaaf6823786e from main