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Re: vacuum, performance, and MVCC

From: Bruce Momjian <bruce(at)momjian(dot)us>
To: PFC <lists(at)peufeu(dot)com>
Cc: pgsql-hackers(at)postgresql(dot)org
Subject: Re: vacuum, performance, and MVCC
Date: 2006-06-27 16:18:23
Message-ID: 200606271618.k5RGINR27070@momjian.us (view raw or flat)
Thread:
Lists: pgsql-hackers
PFC wrote:
> 
> > My idea is that if an UPDATE places the new tuple on the same page as
> > the old tuple, it will not create new index entries for any indexes
> > where the key doesn't change.
> 
> 	Basically the idea behind preventing index bloat by updates is to have  
> one index tuple point to several actual tuples having the same value.
> 	

The idea is not to avoid index bloat, but to allow heap reuse, and having
one index entry for multiple versions of an UPDATEd row is merely an
implementation detail.

-- 
  Bruce Momjian   bruce(at)momjian(dot)us
  EnterpriseDB    http://www.enterprisedb.com

  + If your life is a hard drive, Christ can be your backup. +

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