Message-ID: <4BC4C592.7020400@setonhome.org>
Date: Tue, 13 Apr 2010 15:27:14 -0400
From: Lewis Kapell <lkapell@setonhome.org>
Organization: Seton Home Study School
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To: Kevin Grittner <Kevin.Grittner@wicourts.gov>
CC: pgsql-admin@postgresql.org
Subject: Re: TOAST behavior in 8.3 and 8.4
References: <4BC4BBD4.40706@setonhome.org>
	<4BC4798502000025000307F4@gw.wicourts.gov>
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Thanks for the clarification.

In tuptoaster.h, just above the declaration of TOAST_TUPLES_PER_PAGE, 
there is a comment which begins: "while these can be modified without 
initdb..."

Does this mean that if I reduce the value of TOAST_TUPLE_THRESHOLD and 
rebuild, I can use an existing database cluster without having to run 
initdb again?


On 4/13/2010 3:02 PM, Kevin Grittner wrote:
> Lewis Kapell<lkapell@setonhome.org>  wrote:
>
>> I don't understand what that '256 bytes' refers to.  That is a far
>> cry from 2kb.  I would be grateful if anyone can fill in the
>> evident gap in my knowledge here.
>
> It doesn't try to compress anything unless the tuple (row instance)
> as a whole is above TOAST_TUPLE_THRESHOLD.  In trying to reduce the
> tuple size, it won't consider compressing column values below a
> certain size.  That is where the 256 versus 32 bytes comes in.
>
> -Kevin