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Re: Vacuum v/s Autovacuum

From: Bill Moran <wmoran(at)collaborativefusion(dot)com>
To: "Gauri Kanekar" <meetgaurikanekar(at)gmail(dot)com>
Cc: "Michael Glaesemann" <grzm(at)seespotcode(dot)net>, pgsql-performance(at)postgresql(dot)org
Subject: Re: Vacuum v/s Autovacuum
Date: 2007-01-18 14:05:28
Message-ID: 20070118090528.eec9e398.wmoran@collaborativefusion.com (view raw or flat)
Thread:
Lists: pgsql-performance
In response to "Gauri Kanekar" <meetgaurikanekar(at)gmail(dot)com>:
> On 1/18/07, Michael Glaesemann <grzm(at)seespotcode(dot)net> wrote:
> >
> > On Jan 18, 2007, at 22:24 , Gauri Kanekar wrote:
> >
> > > is autovacuum similar to vacuum full analyse verbose.
> >
> > http://www.postgresql.org/docs/8.2/interactive/routine-
> > vacuuming.html#AUTOVACUUM
> >
> > Apparently, no FULL, no VERBOSE (which is only really useful if you
> > want to see the results, not for routine maintenance).

[please don't top-post]

Actually, you can raise the debugging level in PostgreSQL and get something
similar to VERBOSE.  The only problem is that it also increases the amount
of logging that occurs with everything.

> We have autovacuum ON , but still postgres server warns to
> increas max_fsm_pages value.
> 
> Do autovacuum release space after it is over?

Yes.

If you're still getting warnings about max_fsm_pages while autovac is
running, you need to do one of two things:
1) Increase max_fsm_pages
2) Adjust autovacuum's settings so it vacuums more often.

Depending on this, you may also need to temporarily adjust max_fsm_pages,
then manually vacuum -- you may then find that autovacuum can keep everything
clean with lower settings of max_fsm_pages.

Overall, the best settings for 1 and 2 depend on the nature of your
workload, and simulation and monitoring will be required to find the
best values.  I feel that the docs on this are very good.  If the
amount of data that changes between runs of autovacuum is greater
than max_fsm_pages, then vacuum will be unable to reclaim all the
space.

-- 
Bill Moran
Collaborative Fusion Inc.

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Subject: Re: Vacuum v/s Autovacuum
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