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Re: [pgsql-www] pg_autovacuum is nice ... but ...

From: Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>
To: "Marc G(dot) Fournier" <scrappy(at)postgresql(dot)org>
Cc: Justin Clift <justin(at)postgresql(dot)org>,Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: [pgsql-www] pg_autovacuum is nice ... but ...
Date: 2004-11-29 02:03:54
Message-ID: 200411290203.iAT23sk04399@candle.pha.pa.us (view raw or flat)
Thread:
Lists: pgsql-hackerspgsql-www
Should I add a TODO to warn if FSM values are too small?  Is that doable?

---------------------------------------------------------------------------

Marc G. Fournier wrote:
> 
> Moved to -hackers where this belongs :)
> 
> On Fri, 5 Nov 2004, Justin Clift wrote:
> 
> > Tom Lane wrote:
> > <snip>
> >> Yup. 20000 < 23072, so you're losing some proportion of FSM entries.
> >> What's worse, the FSM relation table is maxed out (1000 = 1000) which
> >> suggests that there are relations not being tracked at all; you have
> >> no idea how much space is getting leaked in those.
> >> 
> >> You can determine the number of relations potentially needing FSM
> >> entries by
> >> 	select count(*) from pg_class where relkind in ('r','i','t');
> >> --- sum over all databases in the cluster to get the right result.
> >> 
> >> Once you've fixed max_fsm_relations, do vacuums in all databases, and
> >> then vacuum verbose should give you a usable lower bound for
> >> max_fsm_pages.
> >
> > Would making max_fsm_relations and max_fsm_pages dynamically update 
> > themselves whilst PostgreSQL runs be useful?  Sounds like they're the 
> > kind of things that many people would receive maximum benefit if 
> > PostgreSQL altered these settings as needed itself.
> 
> I'm not sure if I like this one too much ... but it would be nice if 
> something like this triggered a warning in the logs, maybe a feature of 
> pg_autovacuum itself?
> 
> ----
> Marc G. Fournier           Hub.Org Networking Services (http://www.hub.org)
> Email: scrappy(at)hub(dot)org           Yahoo!: yscrappy              ICQ: 7615664
> 
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-- 
  Bruce Momjian                        |  http://candle.pha.pa.us
  pgman(at)candle(dot)pha(dot)pa(dot)us               |  (610) 359-1001
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