When you have system stats (enabled by default and in fact it's hard to not have it in 10g), you'll have that.
I'm not sure about the actual number. It's probably documented somewhere but I didn't find it. Anybody knows?
If you keep doing:
explain plan for select * from [different size tables]
@?/rdbms/admin/utlxpls
select id, cost, cpu_cost from plan_table;
You may find a pattern. Maybe it's plan_table.cpu_cost divided by sys.aux_stats$.pval1 where pname = 'CPUSPEEDNW' or 'CPUSPEED'?
Yong Huang
[ 本帖最后由 Yong Huang 于 2010-4-6 15:36 编辑 ]
In 9iR2 Performance Tuning Guide, and not in any other documentation, there's this CPU Costing Model:
http://download.oracle.com/docs/ ... 3/ex_plan.htm#19598
---------------- begin quote ----------------
Cost =(#SRds * sreadtim +
#MRds * mreadtim +
#CPUCycles / cpuspeed ) / sreadtim
where:
...
* #CPUCycles is the number of CPU Cycles *)
* sreadtim is the single block read time
...
* cpuspeed is the CPU cycles per second
CPUCycles includes CPU cost of query processing (pure CPU cost) and CPU cost of data retrieval (CPU cost of the buffer cache get).
---------------- end quote ----------------
Yong Huang
