does oracle use something akin to 'estimated LIOs' in order to estimate cost?
Mogens wrote in the oak table book that LIOs do not necessarily translate into CPU. so more LIOs does not necessarily mean more CPU usage. There isn't enough granularity with the different types of LIOs to know which LIOs result in more CPU usage than others.
also, the CBO sometimes is just wrong even with cpu costing. The biggest problems I have had is when i have a table with both Bitmaps and Btree indexes. Oracle occasionally chooses a bitmap when a Btree is more appropriate.
- Original message --------------
> Good afternoon folks...
>
> Continuing our discussion on the optimizer from yesterday. To review:
>
> I have the following statement:
>
> select a.empid, a.ename, b.dname
> from emp a, dept b
> where a.deptno=b.deptno
> and a.empid < 1000
>
--
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Received on Fri Oct 01 2004 - 14:06:32 CDT
