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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
Subject: Re: Huge number of disk writes after migration to 8.1
Date: 2006-01-17 22:12:09
Message-ID: 22030.1137535929@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-bugspgsql-patches
Marcin <migor(at)op(dot)pl> writes:
> Autovacuum is off.
> The VACUUM FULL  bottom line is:
> INFO:  free space map contains 59842 pages in 25371 relations
> DETAIL:  A total of 426720 page slots are in use (including overhead).
> 426720 page slots are required to track all free space.

> And the quick iterations for all the DBs with psql -t -c "\dt" shows
> 67654 rows.

> So there's not 81952, BUT, the tables are created (and dropped) quite
> often during the work hours (and they're regular, not TEMPORARY tables).
>  I also find out, that there were 11170 tables created (and most of them
> dropped) today.

Looking at the code, stats entries for dropped tables are cleaned out
only when a VACUUM command is done; which is something we probably ought
to change.  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?

			regards, tom lane

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