Test nested concurrent transactions with multiple operations.

Nested contexts work correctly.

Test that nested rollback doesn't enable autocommit.

Test nested savepoint rollback while other nested transactions succeed.

Test nested savepoint rollbacks.

Test that nested transactions don't commit if outer fails.

Basic select_related test cases provided by @https://github.com/Terrance. The idea was that on the moment of writing this feature, there were no

Test non-concurrent get_or_create.

Test non-concurrent get_or_create within transaction.

Test not filter on custom enum field.

Test not filter on array field.

Test not_in filter on custom enum field.

Test not_isnull filter on custom enum field.

Now construction.

Now emits CURRENT_TIMESTAMP(6) for MySQL.

Now emits plain CURRENT_TIMESTAMP for non-MySQL dialects.

Now repr.

Nullable FK/O2O relation fields should be optional (default=None) in the schema, not marked as required. This is the fix for issue #1481.

Test .only() combined with .distinct()

Test .only() with no fields (should raise an error)

Test .only() combined with .exclude()

Test .only() combined with .limit()

Test .only() with a field that doesn't exist

Test .only() with just the primary key field

Test .only() with .select_related() for basic functionality

Test .only() combined with .values()