From: | Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> |
---|---|
To: | Manfred Koizar <mkoi-pg(at)aon(dot)at> |
Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Vivek Khera <khera(at)kcilink(dot)com>, pgsql-general(at)postgresql(dot)org, pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: [HACKERS] Decent VACUUM (was: Buglist) |
Date: | 2003-09-05 02:51:48 |
Message-ID: | 200309050251.h852pmN20750@candle.pha.pa.us |
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Lists: | pgsql-general pgsql-hackers |
Manfred Koizar wrote:
> [ still brainstorming ... ]
>
> On Thu, 21 Aug 2003 17:16:50 -0400, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
> wrote:
> >> Whenever a backend encounters a dead tuple it inserts a reference to
> >> its page into the RSM.
> >
> >This assumes that backends will visit dead tuples with significant
> >probability. I doubt that assumption is tenable;
>
> Good point. What about: Whenever a backend *deletes* a tuple it
> inserts a reference to its page into the RSM? Then an entry in the
> RSM doesn't necessarily mean that the referenced page has reclaimable
> space, but it would still be valueable information.
Added to TODO:
* Maintain a map of recently-expired of pages so vacuum can reclaim
free space without a sequential scan
--
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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