Re: Avoiding second heap scan in VACUUM

From: Gregory Stark <stark(at)enterprisedb(dot)com>
To: "Simon Riggs" <simon(at)2ndquadrant(dot)com>
Cc: "Pavan Deolasee" <pavan(dot)deolasee(at)gmail(dot)com>, "Postgres - Hackers" <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Avoiding second heap scan in VACUUM
Date: 2008-05-28 20:55:34
Message-ID: 874p8ip2rd.fsf@oxford.xeocode.com
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"Simon Riggs" <simon(at)2ndquadrant(dot)com> writes:

> So the idea is to have one pass per VACUUM, but make that one pass do
> the first pass of *this* VACUUM and the second pass of the *last*
> VACUUM.

I think that's exactly the same as the original suggestion of having HOT
pruning do the second pass of the last vacuum. The trick is to know whether
the last vacuum committed or not. If it didn't commit then it's not safe to
remove those line pointers yet.

--
Gregory Stark
EnterpriseDB http://www.enterprisedb.com
Ask me about EnterpriseDB's On-Demand Production Tuning

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