Re: HOT breaks CLUSTER, a bit

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: "Heikki Linnakangas" <heikki(at)enterprisedb(dot)com>
Cc: pgsql-hackers(at)postgreSQL(dot)org
Subject: Re: HOT breaks CLUSTER, a bit
Date: 2007-09-12 14:00:54
Message-ID: 20710.1189605654@sss.pgh.pa.us
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"Heikki Linnakangas" <heikki(at)enterprisedb(dot)com> writes:
> Tom Lane wrote:
>> BTW, the proposed HOT code in indexam.c that special-cases SnapshotAny
>> is a crock ...

> It was written under the assumption that all tuples in a HOT chain have
> the same index key, which isn't true after CREATE INDEX as you pointed
> out. Is there something else wrong with it?

It's the wrong special case. It should assume that *all* non-MVCC
snapshots require walking the whole chain.

regards, tom lane

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