Re: TOAST behavior in 8.3 and 8.4

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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@xxxxxxxxxxxxx>  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


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