Re: Slow query problem

On Thu, Jan 08, 2004 at 19:27:16 -0800,
  Mike Glover <mpg4@duluoz.net> wrote:
> 
> You should bump sort_mem as high as you can stand.  with only 8MB sort
> memory available, you're swapping intermediate sort pages to disk --
> a lot. Try the query with sort_mem set to 75MB (to do the entire sort in
> memory). 

Postgres also might be able to switch to a hash aggregate instead of
using a sort if sortmem is made large enough to hold the results for
all of the (estimated) groups.