From: | Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> |
---|---|
To: | Jan Wieck <JanWieck(at)Yahoo(dot)com> |
Cc: | Manfred Koizar <mkoi-pg(at)aon(dot)at>, shridhar_daithankar(at)persistent(dot)co(dot)in, pgsql-general(at)postgresql(dot)org |
Subject: | Re: Buglist |
Date: | 2003-08-26 04:37:00 |
Message-ID: | 200308260437.h7Q4b0802851@candle.pha.pa.us |
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Lists: | pgsql-general pgsql-hackers |
Jan Wieck wrote:
> Manfred Koizar wrote:
> > On Thu, 21 Aug 2003 21:10:34 +0530, "Shridhar Daithankar"
> > <shridhar_daithankar(at)persistent(dot)co(dot)in> wrote:
> >>Point I am trying to make is to tune FSM and autovacuum frequency
> >>such that you catch all the dead tuples in RAM
> >
> > You might be able to catch the pages with dead tuples in RAM, but
> > currently there's no way to keep VACUUM from reading in all the clean
> > pages, which can be far more ...
>
> Which leads us to a zero gravity vacuum, that does the lazy vacuum for
> pages currently available in the buffer cache only. And another pg_stat
> column telling the number of tuples vacuumed so that an autovac has a
> chance to avoid IO consuming vacuum runs for relations where 99% of the
> dead tuples have been caught in memory.
What would be really interesting is to look for dead tuples when you
write/discard a buffer page and add them to the FSM --- that is probably
the latest time you still have access to the page and has the highest
probability of being recyclable.
--
Bruce Momjian | http://candle.pha.pa.us
pgman(at)candle(dot)pha(dot)pa(dot)us | (610) 359-1001
+ If your life is a hard drive, | 13 Roberts Road
+ Christ can be your backup. | Newtown Square, Pennsylvania 19073
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