On 2016-05-23 13:10:29 -0400, Tom Lane wrote: > Andres Freund <and...@anarazel.de> writes: > > One idea I circulated was to fix that by interjecting a special executor > > node to process SRF containing targetlists (reusing Result possibly?). > > That'd allow to remove the isDone argument from ExecEval*/ExecProject* > > and get rid of ps_TupFromTlist which is fairly ugly. > > Would that not lead to, in effect, duplicating all of execQual.c? The new > executor node would still have to be prepared to process all expression > node types.
I don't think it necessarily has to. ISTM that if we add a version of ExecProject()/ExecTargetList() that continues returning multiple rows, we can make the knowledge about the one type of expression we allow to return multiple rows. That'd require a bit of uglyness to implement stuff like SELECT generate_series(1, 2)::text, generate_series(1, 2) * 5; etc. It seems we'd basically have to do one projection step for the SRFs, and then another for the rest. I'm inclined to think that's acceptable to get rid of a lot of the related uglyness. > > One issue with removing targetlist SRFs is that they're currently > > considerably faster than SRFs in FROM: > > I suspect that depends greatly on your test case. But in any case > we could put more effort into optimizing nodeFunctionscan. I doubt you'll find cases where it's significantly the other way round for percall SRFs. The fundamental issue is that targetlist SRFs don't have to spill to a tuplestore, whereas nodeFunctionscan ones have to (even if they're percall). -- Sent via pgsql-hackers mailing list (email@example.com) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers