Date: Mon, 12 Dec 2005 11:50:16 -0700
From: Michael Fuhr <mike@fuhr.org>
To: Merlin Moncure <merlin.moncure@rcsonline.com>
Cc: pgsql-performance@postgresql.org,
	Carlos Benkendorf <carlosbenkendorf@yahoo.com.br>
Subject: Re: How much expensive are row level statistics?
Message-ID: <20051212185016.GA60523@winnie.fuhr.org>
References: <6EE64EF3AB31D5448D0007DD34EEB3417DDAC9@Herge.rcsinc.local>
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On Mon, Dec 12, 2005 at 01:33:27PM -0500, Merlin Moncure wrote:
> > The cost depends on your usage patterns.  I did tests with one of
> > my applications and saw no significant performance difference for
> > simple selects, but a series of insert/update/delete operations ran
> > about 30% slower when block- and row-level statistics were enabled
> > versus when the statistics collector was disabled.
> 
> That approximately confirms my results, except that the penalty may even
> be a little bit higher in the worst-case scenario.  Row level stats hit
> the hardest if you are doing 1 row at a time operations over a
> persistent connection.

That's basically how the application I tested works: it receives
data from a stream and performs whatever insert/update/delete
statements are necessary to update the database for each chunk of
data.  Repeat a few thousand times.

-- 
Michael Fuhr