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Re: [HACKERS] Autovacuum loose ends

From: Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org>
To: Christopher Kings-Lynne <chriskl(at)familyhealth(dot)com(dot)au>
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>,"Matthew T(dot) O'Connor" <matthew(at)zeut(dot)net>,pgsql-patches(at)postgresql(dot)org
Subject: Re: [HACKERS] Autovacuum loose ends
Date: 2005-07-27 20:26:14
Message-ID: 20050727202614.GE1832@alvh.no-ip.org (view raw or flat)
Thread:
Lists: pgsql-hackerspgsql-patches
On Mon, Jul 25, 2005 at 09:31:15AM +0800, Christopher Kings-Lynne wrote:
> >> We have to consider what
> >> happens at stat reset -- AFAICS there's no problem, because as soon as
> >> the table sees some activity, it will be picked up by pgstat.
> >> However, it would be bad if stats are reset right after some heavy
> >> activity on a table.  Maybe the only thing we need is documentation.
> >
> >What's the use-case for having the stat reset feature at all?
> 
> I believe I was the root cause of the pg_stat_reset() function.  The 
> idea at the time was that if you decide to do a round of index 
> optimisation, you want to be able to search for unused indexes and 
> heavily seq. scanned tables.
> 
> If you reset the stats you have 'clean' data to work with.  For 
> instance, you can get 24 hours of clean stats data.

Ok, so there's a reason for having a manual stat-reset.  However what's
the rationale for cleaning stats at postmaster start?  In fact I think
it's actively bad because you lose any data you had before postmaster
stop/crash.

-- 
Alvaro Herrera (<alvherre[a]alvh.no-ip.org>)
"I personally became interested in Linux while I was dating an English major
who wouldn't know an operating system if it walked up and bit him."
(Val Henson)

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