| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Gregory Stark <stark(at)enterprisedb(dot)com> |
| Cc: | "Heikki Linnakangas" <heikki(at)enterprisedb(dot)com>, "Bruce Momjian" <bruce(at)momjian(dot)us>, "PostgreSQL-patches" <pgsql-patches(at)postgresql(dot)org> |
| Subject: | Re: Improvement of procArray.xmin for VACUUM |
| Date: | 2007-03-25 17:35:22 |
| Message-ID: | 7924.1174844122@sss.pgh.pa.us |
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| Lists: | pgsql-patches |
Gregory Stark <stark(at)enterprisedb(dot)com> writes:
> Well I think this would be the same infrastructure we would need to do
> the other discussed improvement to address pg_dump's impact. That
> would require us to publish the youngest xmax of the live
> snapshots. Vacuum could deduce that that xid cannot possibly see any
> transactions between the youngest extant xmax and the oldest
> in-progress transaction.
... and do what with the knowledge? Not remove tuples, because any such
tuples would be part of RECENTLY_DEAD update chains that that xact might
be following now or in the future.
regards, tom lane
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