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Re: Problems with autovacuum

From: Alvaro Herrera
Subject: Re: Problems with autovacuum
Date: ,
Msg-id: 20090526184115.GI32650@alvh.no-ip.org
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In response to: Re: Problems with autovacuum  (Tom Lane)
Responses: Re: Problems with autovacuum  (Tom Lane)
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, ) 
Tom Lane escribió:
> Alvaro Herrera <> writes:
> > Tom Lane escribi�:
> >> I believe the interpretation of autovacuum_naptime is that it should
> >> examine each database that often, ie once a minute by default.  So
> >> it's got more than 30 databases per second to look through.
>
> > Note that this is correct in 8.1 and 8.2 but not 8.3 onwards.
>
> Oh?  The current documentation still defines the variable thusly:
>
>     Specifies the minimum delay between autovacuum runs on any given
>     database. In each round the daemon examines the database and
>     issues VACUUM and ANALYZE commands as needed for tables in that
>     database.

Sorry, it's the other way around actually -- correct for 8.3 onwards,
wrong for 8.1 and 8.2.  In the earlier versions, it would do one run in
a chosen database, sleep during "naptime", then do another run.

> I suppose the use of "minimum" means that this is not technically
> incorrect, but it's sure not very helpful if there is some other
> rule involved that causes it to not behave as I said.  (And if there
> is some other rule, what is that?)

The word "minimum" is there because it's possible that all workers are
busy with some other database(s).

> Please improve the docs.

I'll see about that.

--
Alvaro Herrera                                http://www.CommandPrompt.com/
PostgreSQL Replication, Consulting, Custom Development, 24x7 support

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