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Re: 8.0.3 pg_autovacuum doesn't clear out stats table?

From: "Jim C(dot) Nasby" <jnasby(at)pervasive(dot)com>
To: Robin Iddon <robin(at)edesix(dot)com>
Cc: pgsql-admin(at)postgresql(dot)org
Subject: Re: 8.0.3 pg_autovacuum doesn't clear out stats table?
Date: 2006-02-23 23:58:29
Message-ID: 20060223235829.GP2068@pervasive.com (view raw or flat)
Thread:
Lists: pgsql-admin
On Thu, Feb 23, 2006 at 11:49:46PM +0000, Robin Iddon wrote:
> Jim C. Nasby wrote:
> 
> >Please upgrade.
> >
> >Are you running with the default FSM settings? I'm guessing that
> >pg_statistics has just gotten so large that it's blowing out the FSM.
> >The last few lines from vacuumdb -av would verify that...
> > 
> >
> Jim,
> 
> I am running this in a critical production environment, so I would like 
> to understand whether upgrading is my only option before I do it (I'll 
> need to do some testing first, then organise downtime, etc. - I will do 
> it if required, but would rather a workaround!).  If I do upgrade, I 
> assume you mean upgrade to the current 8.1.x release?

Well, as I mentioned elsewhere, there are some reasons to upgrade to
8.1.x. But no, my comment was specifically about upgrading to the latest
8.0 release. There have been both security and data-loss fixes that you
really should get.

> Yes, I am running with the default FSM settings.
> 
> Here is the output from vacuumdb -v gems (I ran it against my tiny test 
> database, not the production database right now, but remember that even 
> this tiny test database had an enormous pg_statistic table):
> 
> <snip> this is the last few lines as requested
> INFO:  free space map: 182 relations, 25120 pages stored; 98272 total 
> pages needed
> DETAIL:  Allocated FSM size: 1000 relations + 20000 pages = 182 kB 
> shared memory.
> <snip>

You need 100k pages minimum here.

> I don't actually understand exactly what this is telling me though!

Take a look at
http://www.pervasivepostgres.com/lp/newsletters/2005/Insights_opensource_Nov.asp#3
It's a good overview of the FSM, how it works, and how to understand
vacuum verbose output. Though, I guess my opinion is biased since I
wrote it... ;)
-- 
Jim C. Nasby, Sr. Engineering Consultant      jnasby(at)pervasive(dot)com
Pervasive Software      http://pervasive.com    work: 512-231-6117
vcard: http://jim.nasby.net/pervasive.vcf       cell: 512-569-9461

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