Message-ID: <45EF090C.6070503@kaltenbrunner.cc>
Date: Wed, 07 Mar 2007 19:48:44 +0100
From: Stefan Kaltenbrunner <stefan@kaltenbrunner.cc>
User-Agent: Icedove 1.5.0.9 (X11/20061220)
MIME-Version: 1.0
To: Tom Lane <tgl@sss.pgh.pa.us>
CC: Arjen van der Meijden <acmmailing@tweakers.net>,
	pgsql-performance@postgresql.org
Subject: Re: [kris@obsecurity.org: Progress on scaling of FreeBSD
	on 8 CPU systems]
References: <20070227182621.GE29041@decibel.org>
	<20070302150129.GF4885@alvh.no-ip.org>
	<45E84790.6050609@tweakers.net> <45EBF658.30907@tweakers.net>
	<45EC02B4.2070409@kaltenbrunner.cc> <45EC0443.1070107@tweakers.net>
	<45EC7AC3.2030408@kaltenbrunner.cc>
	<22074.1173127131@sss.pgh.pa.us>
In-Reply-To: <22074.1173127131@sss.pgh.pa.us>
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: 7bit

Tom Lane wrote:
> Stefan Kaltenbrunner <stefan@kaltenbrunner.cc> writes:
>> Arjen van der Meijden wrote:
>>> Stefan Kaltenbrunner wrote:
>>>> ouch - do I read that right that even after tom's fixes for the
>>>> "regressions" in 8.2.0 we are still 30% slower then the -HEAD checkout
>>>> from the middle of the 8.2 development cycle ?
>>> Yes, and although I tested about 17 different cvs-checkouts, Tom and I
>>> weren't really able to figure out where "it" happened. So its a bit of a
>>> mystery why the performance is so much worse.
> 
>> double ouch - losing that much in performance without an idea WHY it
>> happened is really unfortunate :-(
> 
> Keep in mind that Arjen's test exercises some rather narrow scenarios;
> IIRC its performance is mostly determined by some complicated
> bitmap-indexscan cases.  So that "30% slower" bit certainly doesn't
> represent an across-the-board figure.  As best I can tell, the decisions
> the planner happened to be making in late June were peculiarly nicely
> suited to his test, but not so much for other cases.

understood - I was not trying to imply that we suffer a 30% performance
drop overall.
But still it means we know about a set of queries that we once could
handle faster than we can now ...

Stefan