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Re: index corruption on composite primary key indexes

From: Alvaro Herrera <alvherre(at)commandprompt(dot)com>
To: "Ng, Stan" <sng(at)automotive(dot)com>
Cc: Mikael Krantz <mk(at)zigamorph(dot)se>, Craig Ringer <craig(at)postnewspapers(dot)com(dot)au>, pgsql-bugs <pgsql-bugs(at)postgresql(dot)org>
Subject: Re: index corruption on composite primary key indexes
Date: 2010-12-16 14:50:00
Message-ID: 1292510876-sup-5298@alvh.no-ip.org (view raw or flat)
Thread:
Lists: pgsql-bugs
Excerpts from Ng, Stan's message of mié dic 15 21:07:57 -0300 2010:

> Now I just need to get my head wrapped around the corner cases of MVCC
> + indexes. From a layman's perspective, it seems the index should only
> operate on the latest version. Perhaps there's a pgsql configuration
> option or hint on the index that I'm missing... The hunt continues!

All tuples need to have index pointers, even the dead ones.  They (the
index pointers to dead tuples) are also cleaned up by vacuum.  There's
an optimization called HOT that allow them to be skipped in some cases;
you may want to read
http://git.postgresql.org/gitweb?p=postgresql.git;a=blob;f=src/backend/access/heap/README.HOT

-- 
Álvaro Herrera <alvherre(at)commandprompt(dot)com>
The PostgreSQL Company - Command Prompt, Inc.
PostgreSQL Replication, Consulting, Custom Development, 24x7 support

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Subject: Re: index corruption on composite primary key indexes
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