Re: Problems with autovacuum

From: Tom Lane
Subject: Re: Problems with autovacuum
Date: ,
Msg-id: 22047.1243382359@sss.pgh.pa.us
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In response to: Re: Problems with autovacuum  (Alvaro Herrera)
Responses: Re: Problems with autovacuum  (Scott Marlowe)
Re: Problems with autovacuum  (Alvaro Herrera)
List: pgsql-performance

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Problems with autovacuum  (Łukasz Jagiełło, )
 Re: Problems with autovacuum  (Scott Marlowe, )
  Re: Problems with autovacuum  (Grzegorz Jaśkiewicz, )
   Re: Problems with autovacuum  (Scott Marlowe, )
   Re: Problems with autovacuum  (Łukasz Jagiełło, )
    Re: Problems with autovacuum  (Tom Lane, )
     Re: Problems with autovacuum  (Łukasz Jagiełło, )
     Re: Problems with autovacuum  (Alvaro Herrera, )
      Re: Problems with autovacuum  (Tom Lane, )
       Re: Problems with autovacuum  (Alvaro Herrera, )
        Re: Problems with autovacuum  (Tom Lane, )
         Re: Problems with autovacuum  (Alvaro Herrera, )
          Re: Problems with autovacuum  (Tom Lane, )
           Re: Problems with autovacuum  (Alvaro Herrera, )
            Re: Problems with autovacuum  (Tom Lane, )
             Re: Problems with autovacuum  (Scott Marlowe, )
             Re: Problems with autovacuum  (Alvaro Herrera, )
              Re: Problems with autovacuum  (Tom Lane, )
               Re: Problems with autovacuum  (Alvaro Herrera, )
                Re: Problems with autovacuum  (Alvaro Herrera, )
                Re: Problems with autovacuum  (Tom Lane, )
       Re: Problems with autovacuum  (Łukasz Jagiełło, )
  Re: Problems with autovacuum  (Łukasz Jagiełło, )
   Re: Problems with autovacuum  (Grzegorz Jaśkiewicz, )

Alvaro Herrera <> 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?

            regards, tom lane


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