The latter ("some unrecognizable unit that only the CBO understands" - though there are probably some mortals that understand it also.) The CBO uses different "weights" for each method it considers, sums the weights for all the methods used in a particular execution plan (which will be the "cost"), and after trying different possibilities, it chooses the execution plan with the smallest total cost. The execution plan with the smallest total cost will also be the execution plan that runs fastest due to the excellence of the algorithm used by the Oracle database engine.
> -----Original Message-----
> Boivin, Patrice J
>
> I am wondering whether the CBO "COST" estimates are in
> seconds, or in some
> unrecognizable unit that only the CBO understands.
>
> In Metalink I found a note stating that we can't even compare
> these values
> between execution plans, they are only valid within each plan.
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Received on Thu Mar 11 2004 - 18:01:00 CST
