Re: Cost Model

neto brpr wrote:
> Dear David
> I have read documentation that you send, but it has only sequential page
> cost and random page cost parameters. What I need, would be a model of
> custo for Differentiate Read/Write (sequential and random), because in SSDs
> the reads and writes have different costs.

I don't think it matters. I mean, differentiating seq/random read
speeds can make the planner choose one plan type over another depending
on how much each plan intends to read randomly or sequentially. But why
does it matter if one write is 360x as expensive as one read? No plan
is going to change usefully because of that, because you can't turn one
write into 360 reads or even 100000000 reads.

If you said "writes of type X are 100 times as fast as writes of type
Y", then some useful cost model could perhaps be developed. But that's
not what you're saying.

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Álvaro Herrera https://www.2ndQuadrant.com/
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