2008/1/29, Vlad Marchenko <[EMAIL PROTECTED]>: > Tom: > > Yes, they are ints. To (somewhat) check your guess on the role of the hash > aggregation speed, I just ran oltp test from sysbench > (http://sysbench.sourceforge.net/docs/#database_mode) on a table with 1mln > of records. That test uses pretty simple queries (that do not use > aggregation) and 8.3 showed about the same performance as 8.2 (strictly > speaking 8.3 was about 1-2% slower, but not 10-15% like on my query). > > I'm curious if that new hash aggregation algorithm was put in 8.3 with the > performance increase as a goal or it was simply a required change to support > some other new feature of 8.3? Right now the switch from 8.2 to 8.3 doesn't > seems a favorable step for the type of application that we have...
Vlad, What happens if you run the 8.3 test with enable_hashagg set to off? Saudações, Clodoaldo Pinto Neto > ----- Original Message ----- > From: "Tom Lane" <[EMAIL PROTECTED]> > To: "Vlad" <[EMAIL PROTECTED]> > Cc: "PG-General" <pgsql-general@postgresql.org> > Sent: Monday, January 28, 2008 9:13 PM > Subject: Re: [GENERAL] 8.3RC2 vs 8.2.6 testing results > > > > Vlad <[EMAIL PROTECTED]> writes: > >> 2. We ran several tests and found 8.3 generally 10% slower than 8.2.6. > > > > The particular case you are showing here seems to be all about the speed > > of hash aggregation --- at least the time differential is mostly in the > > HashAggregate step. What is the data type of a_id? I speculate that > > you're noticing the slightly slower/more complicated hash function that > > 8.3 uses for integers. On a case where the data was well distributed > > you'd not see any countervailing efficiency gain from those extra > > cycles. > > > > regards, tom lane > > > > > ---------------------------(end of broadcast)--------------------------- > TIP 5: don't forget to increase your free space map settings > ---------------------------(end of broadcast)--------------------------- TIP 6: explain analyze is your friend
