Re: New Feature: "Cost Based Transformation"

mccmx_at_hotmail.com wrote:
> Anyone heard of this new feature in 10g: "Cost Based Transformation".
>
> Its basically new functionality which enables the optimizer to cost
> transformation operations like subquery unnesting and predicate pushing
> etc.

I don't understand this concept. Whatever access path is implied by your query-as-written, should still be among the legitimate access paths for the query after it is unnested. So how would it be possible/meaningful for an unnesting not to be costed? It seems like costing the unnesting is an implicit part of the CBO.

Xho

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