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Re: Performance regression on CVS head

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Heikki Linnakangas <heikki(at)enterprisedb(dot)com>
Cc: PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Performance regression on CVS head
Date: 2007-06-05 01:11:44
Message-ID: 2277.1181005904@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-hackers
Heikki Linnakangas <heikki(at)enterprisedb(dot)com> writes:
> I tried to repeat the DBT-2 runs with the "oldestxmin refresh" patch, 
> but to my surprise the baseline run with CVS head, without the patch, 
> behaved very differently than it did back in March.

> I rerun the a shorter 1h test with CVS head from May 20th, and March 6th 
> (which is when I ran the earlier tests), and something has clearly been 
> changed between those dates that affects the test. Test run 248 is with 
> CVS checkout from May 20th, and 249 is from March 6th:

May 20th is not quite my idea of "HEAD" ;-).  It might be worth checking
current code before investing any think-time on this.  But having said
that, it looks a bit like a planner problem --- if I'm reading the
graphs correctly, I/O wait time goes through the roof, suggesting a
change to a much less efficient plan.

			regards, tom lane

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