Re: Performance query about large tables, lots of concurrent access

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