From: Karl Wright <kwright@metacarta.com>
To: Alvaro Herrera <alvherre@commandprompt.com>
Cc: Tom Lane <tgl@sss.pgh.pa.us>
Cc: pgsql-performance@postgresql.org
Subject: Re: Performance query about large tables, lots of concurrent access
Date: Tue, 19 Jun 2007 09:37:10 -0400
Message-ID: <4677DC06.3000300@metacarta.com> (raw)
In-Reply-To: <20070619132643.GC4265@alvh.no-ip.org>
References: <4676DD57.7070304@metacarta.com>
<14291.1182221811@sss.pgh.pa.us>
<4677B831.8060704@metacarta.com>
<4677D298.2010109@metacarta.com>
<20070619132643.GC4265@alvh.no-ip.org>
Alvaro Herrera wrote:
> Karl Wright wrote:
>
>> This particular run lasted four days before a VACUUM became essential.
>> The symptom that indicates that VACUUM is needed seems to be that the
>> CPU usage of any given postgresql query skyrockets. Is this essentially
>> correct?
>
> Are you saying you weren't used to run VACUUM all the time? If so,
> that's where the problem lies.
>
Postgresql 7.4 VACUUM runs for so long that starting it with a cron job
even every 24 hours caused multiple instances of VACUUM to eventually be
running in my case. So I tried to find a VACUUM schedule that permitted
each individual vacuum to finish before the next one started. A vacuum
seemed to require 4-5 days with this particular database - or at least
it did for 7.4. So I had the VACUUM schedule set to run every six days.
I will be experimenting with 8.1 to see how long it takes to complete a
vacuum under load conditions tonight.
Karl
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To: pgsql-performance@postgresql.org
Cc: kwright@metacarta.com, alvherre@commandprompt.com, tgl@sss.pgh.pa.us
Subject: Re: Performance query about large tables, lots of concurrent access
In-Reply-To: <4677DC06.3000300@metacarta.com>
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