| From: | Bruce Momjian <bruce(at)momjian(dot)us> |
|---|---|
| To: | Martijn van Oosterhout <kleptog(at)svana(dot)org> |
| Cc: | Heikki Linnakangas <hlinnaka(at)iki(dot)fi>, Jan Wieck <JanWieck(at)Yahoo(dot)com>, Hannu Krosing <hannu(at)skype(dot)net>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Csaba Nagy <nagy(at)ecircle-ag(dot)com>, Mark Woodward <pgsql(at)mohawksoft(dot)com>, "Jonah H(dot) Harris" <jonah(dot)harris(at)gmail(dot)com>, Christopher Browne <cbbrowne(at)acm(dot)org>, postgres hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: vacuum, performance, and MVCC |
| Date: | 2006-06-26 13:07:43 |
| Message-ID: | 200606261307.k5QD7hF09297@momjian.us |
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| Lists: | pgsql-hackers |
Martijn van Oosterhout wrote:
-- Start of PGP signed section.
> On Mon, Jun 26, 2006 at 07:17:31AM -0400, Bruce Momjian wrote:
> > Correct! We use the same pointers used by normal UPDATEs, except we set
> > a bit on the old tuple indicating it is a single-index tuple, and we
> > don't create index entries for the new tuple. Index scan routines will
> > need to be taught about the new chains, but because only one tuple in
> > the chain is visible to a single backend, the callers should not need to
> > be modified.
>
> I suppose we would also change the index_getmulti() function to return
> a set of ctids plus flags so the caller knows to follow the chains,
> right? And for bitmap index scans you would only remember the page in
> the case of such a tuple, since you can't be sure the exact ctid you've
> got is the one you want.
>
> Seems doable.
Yes, it just is an issue of where you want to add the complexity ---
scan entire page when no free space, or only an UPDATE.
--
Bruce Momjian bruce(at)momjian(dot)us
EnterpriseDB http://www.enterprisedb.com
+ If your life is a hard drive, Christ can be your backup. +
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