From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
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To: | "Pavan Deolasee" <pavan(dot)deolasee(at)gmail(dot)com> |
Cc: | "Simon Riggs" <simon(at)2ndquadrant(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: Hot Standby (commit fest version - v5) |
Date: | 2008-11-20 15:33:02 |
Message-ID: | 2197.1227195182@sss.pgh.pa.us |
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"Pavan Deolasee" <pavan(dot)deolasee(at)gmail(dot)com> writes:
> I wonder if we should refactor lazy_scan_heap() so that *all* the real work
> of collecting information about dead tuples happens only in
> heap_page_prune(). Frankly, there is only a rare chance that a tuple may
> become DEAD after the pruning happened on the page. We can ignore such
> tuples; they will be vacuumed/pruned in the next cycle.
> This would save us a second check of HeapTupleSatisfiesVacuum on the tuples
> which are just now checked in heap_page_prune(). In addition, the following
> additional WAL records are then not necessary because heap_page_prune() must
> have already logged the latestRemovedXid.
I don't think you can do that. Couldn't someone else have run
heap_page_prune between vacuum's first and second visit to the page?
regards, tom lane
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