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Re: planner/optimizer question

From: Jochem van Dieten <jochemd(at)oli(dot)tudelft(dot)nl>
To: pgsql-performance(at)postgresql(dot)org
Subject: Re: planner/optimizer question
Date: 2004-04-30 17:46:24
Message-ID: 409290F0.10509@oli.tudelft.nl (view raw or flat)
Thread:
Lists: pgsql-performance
Manfred Koizar wrote:
> On Wed, 28 Apr 2004 09:05:04 -0400, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>>> [ ... visibility information in index tuples ... ]
>> 
>> Storing that information would at least double the overhead space used
>> for each index tuple.  The resulting index bloat would significantly
>> slow index operations by requiring more I/O.  So it's far from clear
>> that this would be a win, even for those who care only about select
>> speed.
> 
> While the storage overhead could be reduced to 1 bit (not a joke)

You mean adding an isLossy bit and only where it is set the head 
tuple has to be checked for visibility, if it is not set the head 
tuple does not have to be checked?


> we'd
> still have the I/O overhead of locating and updating index tuples for
> every heap tuple deleted/updated.

Would there be additional I/O for the additional bit in the index 
tuple (I am unable to find the layout of index tuple headers in 
the docs)?

Jochem

-- 
I don't get it
immigrants don't work
and steal our jobs
     - Loesje



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