Foreign key constraint in m2m tables is not recreated when altering type of referenced primary key on Oracle.

[Fabio Sangiovanni]

Hi,

I'm experiencing a weird behaviour migrating from Django 3.1.13 to 3.2.6.

With the following setup:

• Python 3.8.10
• PostgreSQL 11.12
• custom user model with AutoField pk
• model (also with AutoField pk) related to User via ManyToManyField

upgrading to Django 3.2.6 with DEFAULT_AUTO_FIELD = 'django.db.models.BigAutoField' leads to a DROP of the foreign key constraints on the (implicit) through model.
The field types on the through model referencing the related models get upgraded correctly; only FK constraints go missing.

I've setup a small reproducer at ​https://github.com/sanjioh/django32fk
Interested tables: app_pet_owner and Django owned ones involving the User model (app_user_groups and app_user_user_permissions).

Please let me know if I can be of further help.

Fabio

[Mariusz Felisiak]

Duplicate of #32743 fixed in Django 4.0+, see 3d9040a50b160f8b4bb580e09f4120d4979fe29e.

[Fabio Sangiovanni]

Hi Mariusz,

thanks, I somehow missed that searching for previous tickets about this issue.

I see that the test in the PR detects the problem in case of model inheritance, while my reproducer triggers it via a ManyToManyField relation.

Do you think an additional test specifically targeting ManyToManyField relations would add any value?

Fabio

[Mariusz Felisiak]

Do you think an additional test specifically targeting ManyToManyField relations would add any value?

Yes it is. I noticed that it doesn't work on Oracle, see ​PR.

[GitHub <noreply@…>]

In 1eb3f500:

Fixed #33057 -- Fixed recreation of foreign key constraints in m2m tables when altering type of referenced primary key on Oracle.