#35679: Existing old migrations with migrations.AlterIndexTogether seem to break
after Django 5.1
--------------------------------+-----------------------------------------
Reporter: Simon Willison | Type: Uncategorized
Status: new | Component: Migrations
Version: 5.1 | Severity: Normal
Keywords: | Triage Stage: Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
--------------------------------+-----------------------------------------
I may be wrong about this, but it appears as if having an existing
migration in a Django project that includes something like this:
{{{
from django.db import migrations, models
class Migration(migrations.Migration):
initial = True
dependencies = []
operations = [
migrations.CreateModel(
name="SubscriberCount",
fields=[
(
"id",
models.AutoField(
auto_created=True,
primary_key=True,
serialize=False,
verbose_name="ID",
),
),
("path", models.CharField(max_length=128)),
("count", models.IntegerField()),
("created", models.DateTimeField(auto_now_add=True)),
("user_agent", models.CharField(db_index=True,
max_length=128)),
],
),
migrations.AlterIndexTogether(
name="subscribercount",
index_together=set([("path", "user_agent", "count",
"created")]),
),
]
}}}
No longer works in the latest Django (I think since 5.1) - attempts to run
migrations produce errors that look like this:
{{{
File "/Users/simon/.local/share/virtualenvs/simonwillisonblog-
izSE3ZQu/lib/python3.10/site-packages/django/db/models/base.py", line 371,
in add_to_class
value.contribute_to_class(cls, name)
File "/Users/simon/.local/share/virtualenvs/simonwillisonblog-
izSE3ZQu/lib/python3.10/site-packages/django/db/models/options.py", line
220, in contribute_to_class
raise TypeError(
TypeError: 'class Meta' got invalid attribute(s): index_together
}}}
If I'm right, this is happening because `index_together` was deprecated
and removed from Django. The problem is that this means projects with
existing migrations can no longer run.
Potential solutions here:
1. Make sure `index_together` in older migrations does not cause an error.
2. Provide documentation describing how to repair projects which are
affected by this bug. I hacked around it with some rough commenting out of
code in old migrations but I'm not at all confident it was the right thing
to do:
https://github.com/simonw/simonwillisonblog/pull/480/commits/f0aa2d69ddeca2acf7badc9ec68dfb7c5b0086ab
3. A combination of the above - make sure it works, but also document what
people should do in an upgrade scenario.
--
Ticket URL: <https://code.djangoproject.com/ticket/35679>
Django <https://code.djangoproject.com/>
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