On Mon, Dec 1, 2008 at 9:32 PM, Greg Smith <[EMAIL PROTECTED]> wrote: > On Mon, 1 Dec 2008, Mark Wong wrote: > >> So then I attempted to see if there might have been difference between the >> executing time of each individual query with the above parameters. The >> queries that don't seem to be effected are Q1, Q4, Q12, Q13, and Q15. Q17 >> suggests that anything higher than default_statistics_target=10 is an >> improvement. The rest of the queries appears not to follow any particular >> trend with respect to default_statistics_target. > > The interesting ones are Q2, Q9, Q17, Q18, and Q20, and that data is much > more useful than the summary. As you mention, Q17 improves significantly > with a higher target. All of the rest are dramatically slower in one or > both tests going from default_statistics_target=10 to 100. Those look like > the most useful data points on the X axis--the increases from 100 up to 1000 > aren't particularly interesting in most of these, except in Q20 where the > "Power Test" seems to oscillate between degrees of good and bad behavior > seemingly at random. > > My picks for the most useful graphs from the long list Mark sent: > > http://207.173.203.223/~markwkm/pgsql/default_statistics_target/q2.png > http://207.173.203.223/~markwkm/pgsql/default_statistics_target/q9.png > http://207.173.203.223/~markwkm/pgsql/default_statistics_target/q17.png > http://207.173.203.223/~markwkm/pgsql/default_statistics_target/q18.png > http://207.173.203.223/~markwkm/pgsql/default_statistics_target/q20.png > > I think the tests you could consider next is to graph the target going from > 10 to 100 in steps of 10 just for those 5 queries. If it gradually > degrades, that's interesting but hard to nail down. But if there's a sharp > transition, getting an explain plan for the two sides of that should provide > some insight. I'm really more interested in the ones that slowed down than > the one that improved, understanding that might finally provide some > evidence against increasing it by default.
I've updated the charts to include results from setting default_statistics_target from 20-90. The links to the charts are the same. The links to the raw data are in http://207.173.203.223/~markwkm/community6/dbt3/ in directories 45-52. Regards, Mark -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
