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Re: Huge number of disk writes after migration to 8.1

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Marcin <migor(at)op(dot)pl>
Cc: pgsql-bugs(at)postgreSQL(dot)org, Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org>
Subject: Re: Huge number of disk writes after migration to 8.1
Date: 2006-01-18 15:20:30
Message-ID: 9008.1137597630@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-bugspgsql-patches
Marcin <migor(at)op(dot)pl> writes:
> On Tue, Jan 17, 2006 at 05:12:09PM -0500, Tom Lane wrote:
>> However, that's always been the case, so I don't understand
>> why your stats file is so much bigger in 8.1.  Have you changed your
>> vacuuming strategy at all since the 8.0 installation?  Perhaps row or
>> block statistics weren't enabled in the 8.0 installation and are now?

> The only change was the upgrade to 8.1. I run VACUUM FULL everyday, and
> double checked that it finished succesfully in last two days. 
> The block and row statistics are disabled:
> stats_start_collector = on
> stats_command_string = off 
> stats_block_level = off
> stats_row_level = off
> stats_reset_on_server_start = off

Stats off and it's still bloating the file??

[ studies code... ]  I see the culprit: it's the pgstat_report_vacuum
and pgstat_report_analyze routines that were added in 8.1.  Those send
messages unconditionally, meaning that the collector will create table
entries for every table during a database-wide vacuum, even with stats
turned off.

This seems like a bad idea.  Given the nature of what's counted, I think
that treating these messages as "row level" stats would be appropriate.
Alvaro, what do you think?

			regards, tom lane

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