| From: | "Heikki Linnakangas" <heikki(at)enterprisedb(dot)com> |
|---|---|
| To: | "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | "Pavan Deolasee" <pavan(dot)deolasee(at)gmail(dot)com>, <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: HOT is applied |
| Date: | 2007-09-21 15:17:50 |
| Message-ID: | 46F3E09E.6060603@enterprisedb.com |
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| Lists: | pgsql-hackers |
Tom Lane wrote:
> I don't much like the idea of adding an xid to the page header --- for
> one thing, *which* xid would you put there, and what would you test it
> against?
I was thinking that you would put the smallest in-progress xmax on the
page there, and you would test it against OldestXmin. If all
transactions commit, there surely isn't anything to prune until that xid
falls beyond the OldestXmin horizon. If an inserting transaction aborts,
we could prune the aborted tuple earlier, but optimizing for aborts
doesn't seem that important.
--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com
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