Simon Charette

@timgraham after thinking more about it the problem is really complex to solve for backends that don't carry over ordering of single derived tables like CockroachDB. The main issue is...

> As mentioned above, the SQL standard (and the Postgres docs) don't guarantee ordering across subqueries I assume you are referring to the F851 feature? I don't have access to...

> If sorting is not chosen, the rows will be returned in an unspecified order. The actual order in that case will depend on the scan and join plan types...

Spent some time working on it in https://github.com/django/django/pull/16040. Still not convinced this should be merged given this is not an issue for any officially supported backends.

buildbot, test on oracle.

@felixxm not sure if it's known but Jenkins Oracle nodes seem to be broken 

Good old Oracle with a surprising failure. From all the tests that do complex union and ordering the one that fails seem pretty trivial https://github.com/django/django/blob/6f80050496780e2f8a65e2a4374dd6375c9fbfa5/tests/queries/test_qs_combinators.py#L418-L422 I don't have an Oracle...

Thanks to both of you! So it seems that we could work around this obscure issue on Oracle by performing a subquery wrapping of the query combination ```sql SELECT *...

FWIW this is still on my radar, I've just been kept away from my keyboard for a while :) I should be able to commit some time in early August.

buildbot, test on oracle.