Le mercredi 21 juillet 2021, 04:25:00 CEST David Rowley a écrit : > Here the test claims that it wants to ensure that the order by using > operator(public.<^) is not pushed down into the foreign scan. > However, unless I'm mistaken, it seems there's a completely wrong > assumption there that the planner would even attempt that. In current > master we don't add PathKeys for ORDER BY aggregates, why would that > sort get pushed down in the first place?
The whole aggregate, including it's order by clause, can be pushed down so there is nothing related to pathkeys here. > > If I adjust that query to something that would have the planner set > pathkeys for, it does push the ORDER BY to the foreign server without > any consideration that the sort operator is not shippable to the > foreign server. > > Am I missing something here, or is postgres_fdw.c's > get_useful_pathkeys_for_relation() just broken? I think you're right, we need to add a check if the opfamily is shippable. I'll submit a patch for that including regression tests. Regards, -- Ronan Dunklau
