Mixing local test models with non-local models resulted in a referential
integrity error during tear down since the models are removed in separate
schema editor instances which each check constraints.
Failure appeared after 7289874adc.
The test was expecting connections used by DiscoverRunner.setup_databases()
to be the ones defined in django.test.runner but this doesn't hold true
since this method was made a proxy of django.test.utils.setup_databases.
This broke the TransactionTestCase.serialized_rollback feature in the test
suite because calls to create_db_test() cleared the test data persisted on
connections objects.
Added an assertions to prevent this from happening again.
This order of operations is more in line with SQLite's documented table
rebuild procedure and ensures that changes aren't committed if foreign key
integrity is broken.
SQLite 3.26 changed the behavior of table and column renaming operations to
repoint foreign key references even if foreign key checks are disabled.
This makes the workarounds in place to simulate this behavior unnecessary on
SQLite 3.26+. Refs #30033.
Refs #29182.
The previous implementation was following a procedure explicitly documented
as incorrect and was the origin of the breakage experienced on SQLite 3.26
release that were addressed by c8ffdbe514.
Thanks to Richard Hipp for pointing out the usage of the incorrect procedure.
Prior to this change foreign key constraint references could be left pointing
at tables dropped during operations simulating unsupported table alterations
because of an unexpected failure to disable foreign key constraint checks.
SQLite3 does not allow disabling such checks while in a transaction so they
must be disabled beforehand.
Thanks ezaquarii for the report and Carlton and Tim for the review.
SQLite 3.26 repoints foreign key constraints on table renames even when
foreign_keys pragma is off which breaks every operation that requires
a table rebuild to simulate unsupported ALTER TABLE statements.
The newly introduced legacy_alter_table pragma disables this behavior
and restores the previous schema editor assumptions.
Thanks Florian Apolloner, Christoph Trassl, Chris Lamb for the report and
troubleshooting assistance.
