| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | "Heikki Linnakangas" <heikki(at)enterprisedb(dot)com> |
| Cc: | "Pavan Deolasee" <pavan(dot)deolasee(at)gmail(dot)com>, "Gregory Stark" <stark(at)enterprisedb(dot)com>, "Bruce Momjian" <bruce(at)momjian(dot)us>, "PostgreSQL-patches" <pgsql-patches(at)postgresql(dot)org> |
| Subject: | Re: HOT patch - version 15 |
| Date: | 2007-09-06 15:06:46 |
| Message-ID: | 22922.1189091206@sss.pgh.pa.us |
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| Lists: | pgsql-patches |
"Heikki Linnakangas" <heikki(at)enterprisedb(dot)com> writes:
> Tom Lane wrote:
>> I don't follow. HOT chains can only get longer by updates.
> Yes. We don't seem to be on the same wavelength...
> Imagine a page with just one tuple on it:
> 1
> After a bunch of updates, it looks like this
> 1 -> 2 -> 3 -> 4 -> 5
> 1 is the tuple the indexes point to, others are heap only.
But if we were attempting prune at every update, at least some of the
later updates should have managed to prune. "2" should certainly be
gone at this point, unless there's lots of contention for the page,
in which case pruning at select won't make things better.
regards, tom lane
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