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
23014	Renaming a field in a unique_together fails	Stephen Burrows	Tim Graham	"To reproduce this, set up a model with two fields and a unique_together constraint. Now try to rename one of the fields to something else. You'll get an error like this (at least for SQLite):

{{{
  File ""./manage.py"", line 10, in <module>
    execute_from_command_line(sys.argv)
  File "".../django/django/core/management/__init__.py"", line 385, in execute_from_command_line
    utility.execute()
  File "".../django/django/core/management/__init__.py"", line 377, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "".../django/django/core/management/base.py"", line 288, in run_from_argv
    self.execute(*args, **options.__dict__)
  File "".../django/django/core/management/base.py"", line 337, in execute
    output = self.handle(*args, **options)
  File "".../django/django/core/management/commands/migrate.py"", line 160, in handle
    executor.migrate(targets, plan, fake=options.get(""fake"", False))
  File "".../django/django/db/migrations/executor.py"", line 62, in migrate
    self.apply_migration(migration, fake=fake)
  File "".../django/django/db/migrations/executor.py"", line 96, in apply_migration
    migration.apply(project_state, schema_editor)
  File "".../django/django/db/migrations/migration.py"", line 107, in apply
    operation.database_forwards(self.app_label, schema_editor, project_state, new_state)
  File "".../django/django/db/migrations/operations/fields.py"", line 84, in database_forwards
    schema_editor.remove_field(from_model, from_model._meta.get_field_by_name(self.name)[0])
  File "".../django/django/db/backends/sqlite3/schema.py"", line 158, in remove_field
    self._remake_table(model, delete_fields=[field])
  File "".../django/django/db/backends/sqlite3/schema.py"", line 110, in _remake_table
    self.create_model(temp_model)
  File "".../django/django/db/backends/schema.py"", line 261, in create_model
    columns = [model._meta.get_field_by_name(field)[0].column for field in fields]
  File "".../django/django/db/models/options.py"", line 420, in get_field_by_name
    % (self.object_name, name))
django.db.models.fields.FieldDoesNotExist: OrderDiscount has no field named 'event_person'
}}}

The only ""workaround"" I was able to find is to first add the ""new"" field, then alter the unique_together constraint, then remove the old field. That works for me since we don't have any data we care about - and if we did, we could just add a data operation - but it seems like this should just work."	Bug	closed	Migrations	1.7-rc-1	Release blocker	fixed		Stephen Burrows mathieu@…	Accepted	1	0	0	0	0	0