On Thu, May 14, 2015 at 07:50:31AM +0200, Andres Freund wrote: > I still believe that the general approach of chaining vs. a union or CTE > is correct due to the efficiency arguments upthread. My problem is > that, unless I very much misunderstand something, the current > implementation can end up requiring roughly #sets * #input of additional > space for the "sidechannel tuplestore" in some bad cases. That happens > if you group by a couple clauses that each lead to a high number of > groups.
Correct. > Andrew, is that a structure you could live with, or not? > > Others, what do you think? Andrew and I discussed that very structure upthread: http://www.postgresql.org/message-id/20141231085845.ga2148...@tornado.leadboat.com http://www.postgresql.org/message-id/87d26zd9k8....@news-spur.riddles.org.uk http://www.postgresql.org/message-id/20141231210553.gb2159...@tornado.leadboat.com I still believe the words I wrote in my two messages cited. -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
