| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | "Pavan Deolasee" <pavan(dot)deolasee(at)gmail(dot)com> |
| Cc: | "Bruce Momjian" <bruce(at)momjian(dot)us>, "Heikki Linnakangas" <heikki(at)enterprisedb(dot)com>, "Florian Pflug" <fgp(dot)phlo(dot)org(at)gmail(dot)com>, "Simon Riggs" <simon(at)2ndquadrant(dot)com>, "Gregory Stark" <stark(at)enterprisedb(dot)com>, PostgreSQL-patches <pgsql-patches(at)postgresql(dot)org> |
| Subject: | Re: HOT patch - version 15 |
| Date: | 2007-09-11 02:11:04 |
| Message-ID: | 9103.1189476664@sss.pgh.pa.us |
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| Lists: | pgsql-patches |
"Pavan Deolasee" <pavan(dot)deolasee(at)gmail(dot)com> writes:
> Pruning removes intermediate dead tuples by marking their line pointers
> ~LP_USED and redirecting the root line pointer to the first
> live/recently_dead tuple in the chain.
It seems utterly unsafe to do this without a vacuum-grade lock on the
page. Someone might be examining the root tuple (eg, in a SnapshotAny
scan) and I think they are entitled to assume that the line pointer
stays valid while they are looking at the tuple.
regards, tom lane
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