RE: Which plan is better - what COST really means ?

>I can't speak for JL but basically I think he's basing cost as the 
optimizer's 
>estimate of IO's to be performed.
Connor,

Which type of IO by your opinion optimizer takes as base type for cost 
estimating?
As far as I know different types of operations (FS, IRS, IQS, IFS, FILTER) 
execute IO differently. I mean CPU utilization is different for single IO 
unit in case of different operations.

Another question is If cost is IO, how optimizer estimates sorting/hash 
etc. actions in IO units?

Jurijs


On 2005.01.15 03:01:20 Connor McDonald wrote:

>I can't speak for JL but basically I think he's basing cost as the 
optimizer's 
>estimate of IO's to be performed.



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