id	summary	reporter	owner	description	type	status	component	version	severity	resolution	keywords	cc	stage	has_patch	needs_docs	needs_tests	needs_better_patch	easy	ui_ux
33462	Altering type of referenced primary key with MTI causes duplicated operations.	bcail	Mariusz Felisiak	"I ran into an intermittent migration issue on Django 4.x and PostgreSQL.
The migrations work fine on Django 3.2.x, but intermittently fail on
Django 4.x with the following exception:

django.db.utils.ProgrammingError: constraint
""polls_questioncontribution_base_question_id_25bfb2a8_fk"" for relation
""polls_questioncontribution"" already exists

I made a small demo repo to show the problem:
https://github.com/bcail/migration_error. I put the sqlmigrate output
from Django 3.2 and Django 4 in the repo, and it looks like Django 4
(sometimes) creates duplicate SQL statements.

I also ran git bisect on the Django code, and it looks like the problem
starts showing up with this commit:
https://github.com/django/django/commit/3d9040a50b160f8b4bb580e09f4120d4979fe29e."	Bug	closed	Migrations	4.0	Release blocker	fixed		David Wobrock	Accepted	1	0	0	0	0	0