On Mon, Nov 5, 2012 at 2:40 PM, Claudio Freire <klaussfreire@xxxxxxxxx> wrote: > On Mon, Nov 5, 2012 at 2:09 PM, Jeff Janes <jeff.janes@xxxxxxxxx> wrote: >>>> In my experience when doing sorts in isolation, having more work_mem >>>> is a bad thing, unless it enables you to remove a layer of >>>> tape-merging. I always blamed it on the L1/L2 etc. levels of caching. >>> >>> Blame it on quicksort, which is quite cache-unfriendly. >> >> The observation applies to heap sort. > > Well, heapsort is worse, but quicksort is also quite bad. Here[0], an interesting analysis. I really believe quicksort in PG (due to its more complex datatypes) fares a lot worse. [0] http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&ved=0CD0QFjAB&url=http%3A%2F%2Fwww.cs.auckland.ac.nz%2F~mcw%2FTeaching%2Frefs%2Fsorting%2Fladner-lamarca-cach-sorting.pdf&ei=PPqXUMnEL9PaqQHntoDgDQ&usg=AFQjCNE3mDf6ydj1MHUzfQw13TccOa895A -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
