Django 5.1 Migration Issue with AlterIndexTogether

You're encountering a known issue when upgrading to Django 5.1.3 with historical migrations that use AlterIndexTogether. This is indeed problematic because while the documentation states that AlterIndexTogether is maintained for backward compatibility with pre-Django 4.2 migration files, the error you're seeing suggests there's an implementation issue.

Understanding the Issue

The error TypeError: 'class Meta' got invalid attribute(s): index_together occurs because in Django 5.1, the index_together option has been fully removed from the Meta class validation, even though the migration operation itself is still part of the public API.

Possible Workarounds

Since squashing migrations doesn't solve your problem (as it doesn't remove the problematic operation), here are some potential workarounds:

1. Create a custom migration operation that replaces AlterIndexTogether but doesn't trigger the validation error:

   PYTHONCopied
   from django.db.migrations.operations.models import AlterIndexTogether as DjangoAlterIndexTogether
   
   class CustomAlterIndexTogether(DjangoAlterIndexTogether):
       def state_forwards(self, app_label, state):
           # Custom implementation that doesn't set index_together on the model's Meta
           # but still performs the database changes
           pass

2. Manually edit historical migrations to replace AlterIndexTogether with equivalent AddIndex and RemoveIndex operations.

3. Create a fake initial migration that represents the current state of your database schema, and use that as a starting point for future migrations, effectively bypassing the historical migrations.

Filing a Bug Report

Given that the documentation explicitly states that AlterIndexTogether should still work for backward compatibility reasons, but it's failing in practice, filing a new bug ticket would be appropriate. This appears to be a regression in Django 5.1 where the backward compatibility promise isn't being fulfilled.

When filing the bug, include:

• The exact error message
• Your Django version (5.1.3)
• A minimal reproduction case showing a pre-Django 4.2 migration with AlterIndexTogether failing
• References to the related tickets you mentioned (#35749 and #34856)

This would help the Django team address the inconsistency between the documented behavior and the actual implementation.