Re: CBO calculates lower cost, but runs slower...

I thought this thread was based on trying to solve a problem on a single database; however, let me rephrase:

on a specific database
with specific set of values for the session parameters on a fixed set of data
for a given set of values for the statistics

(and I think that covers all the bases - and perhaps it ought to be noted on the FAQ)

then the path with the lowest cost if the one which the cost-based optimizer thinks will be the fastest way to satisfy the query according to the specific requirements of the optimizer goal.

--
Jonathan Lewis
http://www.jlcomp.demon.co.uk

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

Author of:
Practical Oracle 8i: Building Efficient Databases

Screen saver or Life saver: http://www.ud.com
Use spare CPU to assist in cancer research.

Nuno Souto wrote in message <3bfa2578.4831636_at_news>...


>In a sudden spasm of awareness,

>Jonathan Lewis doodled thusly:

>

>>

>>For a given SQL statement and optimizer goal, the

>>lowest cost is supposed to be the fastest query path.

>

>Even across databases, Jonathan?  I got the feeling his problem was

>that one db gave him one result, the other another.

>

>

>Cheers

>Nuno Souto

>nsouto_at_optushome.com.au.nospam