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Re: Where to find information on the new HOT tables?

From: Dimitri Fontaine <dfontaine(at)hi-media(dot)com>
To: Bruce Momjian <bruce(at)momjian(dot)us>
Cc: pgsql-admin(at)postgresql(dot)org, Alvaro Herrera <alvherre(at)commandprompt(dot)com>, Chris Hoover <revoohc(at)gmail(dot)com>
Subject: Re: Where to find information on the new HOT tables?
Date: 2008-02-07 20:00:17
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-admin
Le Thursday 07 February 2008 20:43:57 Bruce Momjian, vous avez écrit :
> Does the release note item on HOT need additions?

If I put the release not item on HOT here:

Heap-Only Tuples (HOT) accelerate space reuse for most UPDATEs and DELETEs 
(Pavan Deolasee, with ideas from many others) 

UPDATEs and DELETEs leave dead tuples behind, as do failed INSERTs. Previously 
only VACUUM could reclaim space taken by dead tuples. With HOT dead tuple 
space can be reclaimed at the time of INSERT or UPDATE if no changes are made 
to indexed columns. This allows for more consistent performance. Also, HOT 
avoids adding duplicate index entries.

I'd say it only misses the transparent & automatic precision, telling the 
users they don't have anything to do about HOT: PostgreSQL is able on its own 
to decide when HOT is or is not safe to use.
And I have to get it back that documentation is not verbose enough about how 
HOT is working, just that you have to know where to look...

What about Alvaro's concern about manual vacuuming policies editing wrt to 


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