#23014: Renaming a field in a unique_together fails
----------------------------+----------------------
Reporter: melinath | Owner: nobody
Type: Bug | Status: new
Component: Migrations | Version: 1.7-rc-1
Severity: Normal | Keywords:
Triage Stage: Unreviewed | Has patch: 0
Easy pickings: 0 | UI/UX: 0
----------------------------+----------------------
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.
--
Ticket URL: <https://code.djangoproject.com/ticket/23014>
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