Re: Problems with autovacuum - Mailing list pgsql-performance

From Scott Marlowe
Subject Re: Problems with autovacuum
Date
Msg-id dcc563d10905261857s31218249ga7bb33c953a7b748@mail.gmail.com
Whole thread Raw
In response to Re: Problems with autovacuum  (Tom Lane <tgl@sss.pgh.pa.us>)
List pgsql-performance
2009/5/26 Tom Lane <tgl@sss.pgh.pa.us>:
> Alvaro Herrera <alvherre@commandprompt.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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