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
25752	RenameField on m2m causes error when new m2m field is added with old name	skyjur	nobody	"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."	Bug	closed	Migrations	1.7	Normal	duplicate	postgres migrations renamefield		Unreviewed	0	0	0	0	0	0