Proxy model foreign keys not created properly by syncdb
|Reported by:||akaariai||Owned by:||nobody|
|Component:||Database layer (models, ORM)||Version:||1.4|
|Has patch:||no||Needs documentation:||no|
|Needs tests:||no||Patch needs improvement:||yes|
Add this test to modeltests/proxy_models/tests.py:
class TransactionalProxyModelTests(TransactionTestCase): def test_proxy_fk(self): """ Test that the DB contains proper foreign keys for proxy model references. """ @transaction.commit_on_success def create_failing_pk(): t = TrackerUser.objects.create(status='bar') Improvement.objects.create(summary='foof', version='foof', reporter_id=1, associated_bug_id=1, assignee=t) self.assertRaises(IntegrityError, create_failing_pk)
On MySQL this does not fail when using InnoDB. It should fail, as both reporter and associated bug with ID=1 are missing.
The reason for this is that in django/db/backends/creation.py, sql_for_pending_references() is a check:
if not model._meta.managed or model._meta.proxy: skip creation
Now, that is incorrect: the model in question is the model we are _referring_, not the model from where the PK is from. So, under MySQL foreign keys to proxy models do not get enforced in the DB.
In addition the same bug is there for other databases, too. However, this one does not show under PostgreSQL as the foreign key is created inline. However, were the order of the models different in models.py also PostgreSQL would fail to create the foreign key.
The fix is luckily very simple: just remove the "or proxy" part. The managed part is correct: the referenced model can be a view for example, in which case referencing it would be a failure.