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Re: Stats collector performance improvement

From: Jan Wieck <JanWieck(at)Yahoo(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>, pgsql-hackers(at)postgreSQL(dot)org
Subject: Re: Stats collector performance improvement
Date: 2006-01-03 04:06:57
Message-ID: 43B9F861.5040207@Yahoo.com (view raw or flat)
Thread:
Lists: pgsql-hackerspgsql-patchespgsql-performance
On 1/2/2006 3:20 PM, Tom Lane wrote:

> [ moving to -hackers ]
> 
> Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> writes:
>> I did some research on this because the numbers Tom quotes indicate there
>> is something wrong in the way we process stats_command_string
>> statistics.
>> [ ... proposed patch that seems pretty klugy to me ... ]
> 
> I wonder whether we shouldn't consider something more drastic, like
> getting rid of the intermediate stats buffer process entirely.
> 
> The original design for the stats communication code was based on the
> premise that it's better to drop data than to make backends wait on

The original design was geared towards searching for useless/missing 
indexes and tuning activity like that. This never happened, but instead 
people tried to use it as a reliable debugging or access statistics aid 
... which is fine but not what it originally was intended for.

So yes, I think looking at what it usually is used for, a message 
passing system like SysV message queues (puke) or similar would do a 
better job.


Jan

> the stats collector.  However, as things have turned out I think this
> notion is a flop: the people who are using stats at all want the stats
> to be reliable.  We've certainly seen plenty of gripes from people who
> are unhappy that backend-exit messages got dropped, and anyone who's
> using autovacuum would really like the tuple update counts to be pretty
> solid too.
> 
> If we abandoned the unreliable-communication approach, could we build
> something with less overhead?
> 
> 			regards, tom lane


-- 
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