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Re: Stats collector performance improvement

From: "Qingqing Zhou" <zhouqq(at)cs(dot)toronto(dot)edu>
To: pgsql-hackers(at)postgresql(dot)org
Subject: Re: Stats collector performance improvement
Date: 2006-01-02 21:03:20
Message-ID: dpc4cg$lm6$1@news.hub.org (view raw or flat)
Thread:
Lists: pgsql-hackerspgsql-patchespgsql-performance
"Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote
>
> 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 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.
>

AFAICS if we can maintain the stats counts solid, then it may hurt 
performance dramatically. Think if we maintain 
pgstat_count_heap_insert()/pgstat_count_heap_delete() pretty well, then we 
get a replacement of count(*). To do so, I believe that will add another 
lock contention on the target table stats.

Regards,
Qingqing 



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