RE: prefixed index - high clustering factor & high cpu

Please supply the tkprof output you are using to get these figures.

Is your "cost about 30k" from the Rowsource Operation output, showing "time = 30000 microseconds" ? Or is it actually from a plan_table.

If the latter, then a CPU cost of around 30,000 (Oracle operations) is perfectly reasonable for 4 buffer visits to acquire a single row by unique index.

Regards

Jonathan Lewis
http://jonathanlewis.wordpress.com

Author: Cost Based Oracle: Fundamentals
http://www.jlcomp.demon.co.uk/cbo_book/ind_book.html

The Co-operative Oracle Users' FAQ
http://www.jlcomp.demon.co.uk/faq/ind_faq.html

• Original Message -----
  > Subject: RE: prefixed index - high clustering factor & high cpu
  

>at the tkprof the cpu cost is very high , its about 30k, rows returned
> is 1 , io cost is 4 , the cost itself only 4.

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