On 01/27/2014 08:48 AM, Mitsumasa KONDO wrote: > > > The issue of concern is not the performance of pg_stat_statements, > AUIU. The issue is whether this patch affects performance > generally, i.e. is there a significant cost in collecting these > extra stats. To test this you would compare two general pgbench > runs, one with the patch applied and one without. > > I showed first test result which is compared with without > pg_stat_statements and without patch last day. They ran in same server > and same benchmark settings(clients and scale factor) as today's > result. When you merge and see the results, you can confirm not to > affect of performance in my patch. > >
Yeah, sorry, I misread your message. I think this is good to go from a performance point of view, although I'm still a bit worried about the validity of the method (accumulating a sum of squares). OTOH, Welford's method probably requires slightly more per statement overhead, and certainly requires one more accumulator per statement. I guess if we find ill conditioned results it wouldn't be terribly hard to change. cheers andrew -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
