"Jonathan Hoover" <jhoover@xxxxxxxxxxxxx> writes: > [ poor performance with NOT IN ] > Query E then is apparently the way to go, but shouldn't there be a way > to get the query planner to take these steps itself? If A had ever > finished, I'd sure like to have seen an EXPLAIN ANALYZE on it. Well, just an EXPLAIN would have told you what the plan was like. What I suspect was happening was that your manipulations of the query altered the planner's estimate of the number of rows in the NOT IN's subquery, causing it to pick (or not) a hash-table-based implementation of NOT IN. The hashed approach is a lot faster but requires the subquery's output to fit in work_mem. In general, NOT IN is hard to optimize because of its weird behavior for NULLs. I'd suggest looking into converting the query to use an EXISTS instead. regards, tom lane -- Sent via pgsql-admin mailing list (pgsql-admin@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-admin
