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Re: Problems with autovacuum

From: Scott Marlowe <scott(dot)marlowe(at)gmail(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Alvaro Herrera <alvherre(at)commandprompt(dot)com>, Łukasz Jagiełło <lukasz(dot)jagiello(at)gforces(dot)pl>, Grzegorz Jaśkiewicz <gryzman(at)gmail(dot)com>, pgsql-performance(at)postgresql(dot)org
Subject: Re: Problems with autovacuum
Date: 2009-05-27 01:57:00
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-performance
2009/5/26 Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>:
> Alvaro Herrera <alvherre(at)commandprompt(dot)com> writes:
>> However I think there's a bigger problem here, which is that if the user
>> has set naptime too low, i.e. to a value lower than
>> number-of-databases * 100ms, we'll be running the (expensive)
>> rebuild_database_list function on each iteration ... maybe we oughta put
>> a lower bound on naptime based on the number of databases to avoid this
>> problem.
> Bingo, that's surely exactly what was happening to the OP.  He had 2000
> databases and naptime at (I assume) the default; so he was rerunning
> rebuild_database_list every 100ms.
> So that recovery code path needs some more thought.  Maybe a lower bound
> on how often to do rebuild_database_list?  And/or don't set adl_next_worker
> to less than 100ms in the future to begin with?

I'd be happy with logging telling me when things are getting pathological.

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