From: Stefan Kaltenbrunner <stefan@kaltenbrunner.cc>
To: Bruce Momjian <pgman@candle.pha.pa.us>
Cc: Qingqing Zhou <zhouqq@cs.toronto.edu>
Cc: pgsql-hackers@postgresql.org
Subject: Re: Test request for Stats collector performance improvement
Date: Fri, 16 Jun 2006 18:12:50 +0200
Message-ID: <4492D882.6030109@kaltenbrunner.cc> (raw)
In-Reply-To: <200606161603.k5GG3MS27858@candle.pha.pa.us>
References: <200606161603.k5GG3MS27858@candle.pha.pa.us>
Bruce Momjian wrote:
> OK, based on reports I have seen, generally stats_query_string adds 50%
> to the total runtime of a "SELECT 1" query, and the patch reduces the
> overhead to 25%.
that is actually not true for both of the platforms(a slow OpenBSD
3.9/x86 and a very fast Linux/x86_64) I tested on. Both of them show
virtually no improvement with the patch and even worst it causes
considerable (negative) variance on at least the Linux box.
>
> However, that 25% is still much too large. Consider that "SELECT 1" has
> to travel from psql to the server, go through the
> parser/optimizer/executor, and then return, it is clearly wrong that the
> stats_query_string performance hit should be measurable.
>
> I am actually surprised that so few people in the community are
> concerned about this. While we have lots of people studying large
> queries, these small queries should also get attention from a
> performance perspective.
>
> I have created a new test that also turns off writing of the stats file.
> This will not pass regression tests, but it will show the stats write
> overhead.
will try to run those too in a few.
Stefan
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Reply to all the recipients using the --to and --cc options:
reply via email
To: pgsql-performance@postgresql.org
Cc: stefan@kaltenbrunner.cc, pgman@candle.pha.pa.us, zhouqq@cs.toronto.edu, pgsql-hackers@postgresql.org
Subject: Re: Test request for Stats collector performance improvement
In-Reply-To: <4492D882.6030109@kaltenbrunner.cc>
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
This inbox is served by DDX for PostgreSQL; see mirroring instructions
for how to clone and mirror all data and code used for this inbox