> "Gary Doades" <gpd@xxxxxxxxxxxx> writes: >> I think the reason I wasn't seeing performance issues with normal sort >> operations is because they use work_mem not maintenance_work_mem which >> was >> only set to 2048 anyway. Does that sound right? > > Very probable. Do you want to test the theory by jacking that up? ;-) Hmm, played around a bit. I have managed to get it to do a sort on one of the "bad" columns using a select of two whole tables that results in a sequntial scan, sort and merge join. I also tried a simple select column order by column for a bad column. I tried varying maintenance_work_mem and work_mem up and down between 2048 and 65536 but I always get similar results. The sort phase always takes 4 to 5 seconds which seems about right for 900,000 rows. This was on a colunm that took 12 minutes to create an index on. I've no idea why it should behave this way, but probably explains why I (and others) may not have noticed it before. Regards, Gary.
