From: | Karl Wright <kwright(at)metacarta(dot)com> |
---|---|
To: | Alvaro Herrera <alvherre(at)commandprompt(dot)com> |
Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, pgsql-performance(at)postgresql(dot)org |
Subject: | Re: Performance query about large tables, lots of concurrent access |
Date: | 2007-06-19 13:37:10 |
Message-ID: | 4677DC06.3000300@metacarta.com |
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Lists: | pgsql-performance |
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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