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Proposed patch for ANALYZE overcounting dead rows

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: pgsql-patches(at)postgreSQL(dot)org
Subject: Proposed patch for ANALYZE overcounting dead rows
Date: 2007-11-16 22:58:23
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-patches
There's been a thread in pgsql-performance about ANALYZE reporting an
overly large number of dead rows because it counts anything that's not
visible-per-SnapshotNow-rules as "dead", in particular
insert-in-progress tuples are reported as "dead".  This seems a bad
idea because it may prompt autovacuum to launch a useless vacuum.

The attached patch revises ANALYZE to distinguish tuple states the same
way VACUUM does, and to not count INSERT_IN_PROGRESS nor
DELETE_IN_PROGRESS tuples as either "live" or "dead".

Comments?  In particular, should we report a count of in-doubt tuples in
the eventual LOG message, and does anyone want to argue for still
counting DELETE_IN_PROGRESS as "dead"?

			regards, tom lane

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