On Thu, Apr 21, 2005 at 08:24:15AM -0400, Jeff wrote: > > On Apr 21, 2005, at 7:49 AM, Shoaib Burq (VPAC) wrote: > > >Now I have not touch the $PGDATA/postgresql.conf (As I know very little > >about memory tuning) Have run VACCUM & ANALYZE. > > > You should really, really bump up shared_buffers and given you have 8GB > of ram this query would likely benefit from more work_mem. > > >and the time taken is *twice* that for the original. The modification > >was > >minor. The queries do make use of both CPUs: > > > Is this an IO intensive query? If running both in parellel results in > 2x the run time and you have sufficient cpus it would (to me) indicate > you don't have enough IO bandwidth to satisfy the query. >
I would add to Jeff's comments, that the default configuration parameters are fairly-to-very conservative which tends to produce plans with more I/O. Bumping your shared_buffers, work_mem, and effective_cache_size should allow the planner to favor plans that utilize more memory but require less I/O. Also, with small amounts of work_mem, hash joins cannot be used and the planner will resort to nested loops. Ken ---------------------------(end of broadcast)--------------------------- TIP 7: don't forget to increase your free space map settings
