Johann Spies <johann.spies@xxxxxxxxx> writes: > I would appreciate some help optimising the following query: It's a mistake to imagine that indexes are going to help much with a join of this size. Hash or merge join is going to be a lot better than nestloop. What you need to do is make sure those will perform as well as possible, and to that end, it'd likely help to raise work_mem. I'm not sure if you can sanely put it high enough to make the query operate totally in memory --- it looks like you'd need work_mem of 500MB or more to prevent any of the sorts or hashes from spilling to disk, and keep in mind that this query is going to use several times work_mem because there are multiple sorts/hashes going on. But if you can transiently dedicate a lot of RAM to this query, that should help some. I'd suggest increasing work_mem via a SET command in the particular session running this query --- you don't want such a high value to be the global default. regards, tom lane -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
