inspectdb creates a redundant unique_together for composite primary keys

[Baptiste Mispelon]

With the following table:

CREATE TABLE example (
    a integer,
    b integer,
    c integer,
    PRIMARY KEY (a, c)
);

Running inspectdb produces the following model definition:

class Example(models.Model):
    pk = models.CompositePrimaryKey('a', 'c')
    a = models.IntegerField()
    b = models.IntegerField(blank=True, null=True)
    c = models.IntegerField()

    class Meta:
        managed = False
        db_table = 'example'
        unique_together = (('a', 'c'),)

I'm pretty sure the last unique_together = (('a', 'c'),) is redundant since the pk = models.CompositePrimaryKey('a', 'c') already implies uniqueness, no?

[Baptiste Mispelon]

Here's a draft PR with a test and a fix: ​https://github.com/django/django/pull/19430

I'll add release notes if the ticket is accepted.

[Simon Charette]

Thanks for the report Baptiste.

Marked as a bug in a newly released feature.

[nessita <124304+nessita@…>]

In 66f9eb0f:

Fixed #36357 -- Skipped unique_together in inspectdb output for composite primary keys.

Thanks to Baptiste Mispelon for the report and quick fix, and to Simon
Charette and Jacob Walls for the reviews.

Co-authored-by: Natalia <124304+nessita@…>

[Natalia <124304+nessita@…>]

In 1367a197:

[5.2.x] Fixed #36357 -- Skipped unique_together in inspectdb output for composite primary keys.

Thanks to Baptiste Mispelon for the report and quick fix, and to Simon
Charette and Jacob Walls for the reviews.

Co-authored-by: Natalia <124304+nessita@…>

Backport of 66f9eb0ff1e7147406318c5ba609729678e4e6f6 from main.