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From: Shaun Thomas <sthomas@peak6.com>
To: Scott Marlowe <scott.marlowe@gmail.com>
Cc: felix <crucialfelix@gmail.com>
Cc: pgsql-performance@postgresql.org <pgsql-performance@postgresql.org>
Subject: Re: good old VACUUM FULL
Date: Wed, 23 Mar 2011 08:13:28 -0500
Message-ID: <4D89F1F8.1080609@peak6.com> (raw)
In-Reply-To: <AANLkTi=TfxNpFW-v1vFBjtJLqnWL=Rcu8DrqaL_0KDL5@mail.gmail.com>
References: <AANLkTi=SMx4GiW5DLFTpOm4Go-ibipc6WpTN+4rY7tbF@mail.gmail.com>
	<AANLkTi=TfxNpFW-v1vFBjtJLqnWL=Rcu8DrqaL_0KDL5@mail.gmail.com>

On 03/23/2011 01:16 AM, Scott Marlowe wrote:

> Then either cluster failed (did you get an error message) or the table
> was not bloated.  Given that it looks like it was greatly reduced in
> size by the vacuum full, I'd guess cluster failed for some reason.

Or it just bloated again. Remember, he still hasn't changed his 
max_fsm_pages setting, and that table apparently experiences *very* high 
turnover.

A 25x bloat factor isn't unheard of for such a table. We have one that 
needs to have autovacuum or be manually vacuumed frequently because it 
experiences several thousand update/deletes per minute. The daily 
turnover of that particular table is around 110x. If our fsm settings 
were too low, or we didn't vacuum regularly, I could easily see that 
table quickly becoming unmanageable. I fear for his django_session table 
for similar reasons.

Felix, I know you don't want to "experiment" with kernel parameters, but 
you *need* to increase your max_fsm_pages setting.

-- 
Shaun Thomas
OptionsHouse | 141 W. Jackson Blvd. | Suite 800 | Chicago IL, 60604
312-676-8870
sthomas@peak6.com

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