Date: Tue, 24 Apr 2007 22:07:10 -0400
From: Robert Treat <xzilla@users.sourceforge.net>
Subject: Re: row-level stats and last analyze time
In-reply-to: <1177450739.16415.249.camel@localhost.localdomain>
To: pgsql-docs@postgresql.org
Cc: Neil Conway <neilc@samurai.com>,
	Guillaume Lelarge <guillaume@lelarge.info>,
	pgsql-hackers <pgsql-hackers@postgresql.org>, Tom Lane <tgl@sss.pgh.pa.us>
Message-id: <200704242207.11093.xzilla@users.sourceforge.net>
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On Tuesday 24 April 2007 17:38, Neil Conway wrote:
> [ CC'ing -hackers ]
>
> On Sun, 2007-04-22 at 16:10 +0200, Guillaume Lelarge wrote:
> > This patch adds a sentence on monitoring.sgml explaining that
> > stats_row_level needs to be enabled if user wants to get last
> > vacuum/analyze execution time.
>
> This behavior was introduced in r1.120 of postmaster/pgstat.c:
>
>     Modify pgstats code to reduce performance penalties from
>     oversized stats data files: avoid creating stats
>     hashtable entries for tables that aren't being touched
>     except by vacuum/analyze [...]
>
> which included other modifications to reduce the pgstat I/O volume in
> 8.1. I don't think this particular change was wise: the reduction in
> pgstat volume is pretty marginal, and it is counter-intuitive for
> stats_row_level to effect whether the last ANALYZE / VACUUM is recorded.
> (Plus, the optimization is not even enabled with the default
> postgresql.conf settings.)
>

+1

-- 
Robert Treat
Build A Brighter LAMP :: Linux Apache {middleware} PostgreSQL