RenameField on m2m causes error when new m2m field is added with old name

[skyjur]

Given I have a field

   many = ManyToManyField()

I create a migration:

   RenameField: "many" to "many_legacy"
   Create Field: "many" as ManyToManyField()

When I run the migration I get:

...
  File "django/db/backends/utils.py", line 64, in execute
    return self.cursor.execute(sql, params)
  File "django/db/utils.py", line 97, in __exit__
    six.reraise(dj_exc_type, dj_exc_value, traceback)
  File "django/db/backends/utils.py", line 64, in execute
    return self.cursor.execute(sql, params)
django.db.utils.ProgrammingError: relation "cms_test_many_2e06cda4" already exists

It seems the problem is that RenameField does not rename database indexes, and then when new m2m field is being added it tries to create index with same name and so I get database error.

Here is full migration code which throws this error:

class Migration(migrations.Migration):

    dependencies = [
    ]

    operations = [
        migrations.RenameField(
            'test',
            'many',
            'many_legacy',
        ),
        migrations.AddField(
            model_name='test',
            name='many',
            field=models.ManyToManyField(to='cms.NewRel2'),
        ),
    ]

Initially I noticed this error on 1.7, then I also managed to replicate it on 1.8

Error happened on postgres database.

[skyjur]

The workaround I used was to rename those sql indexes with additional RunSQL:

    migrations.RunSQL(
        'alter table cms_test_many_2e06cda4 rename to cms_test_many_legacy_2e06cda4',
        'alter table cms_test_many__legacy_2e06cda4 rename to cms_test_many_2e06cda4'
    )

[Tim Graham]

Could it be a duplicate of #23577?