Oracle FAQ | Your Portal to the Oracle Knowledge Grid |
Home -> Community -> Usenet -> c.d.o.server -> Re: EXPLAIN PLAN : better with RULE!
Oh dear -
I have to contradict you twice in one day.
Having done a bit of stress-testing and generally having fun with the optimisers, I can tell you that one test involving 255 tables gave me an optimisation time of:
Rule 45 minutes 22 seconds all_rows 3.04 seconds first_rows 3.04 seconds
The CBO usually finds optimal paths in complex joins despite the best efforts of designers and dbas to confuse the issue with unsuitable indexing strategies, inappropriate statistics, and misleading resource definitions.
-- Jonathan Lewis http://www.jlcomp.demon.co.uk Next Seminars UK Sept Australia August Malaysia September USA x 2 November http://www.jlcomp.demon.co.uk/seminar.html Alex Filonov wrote in message <336da121.0207180744.cea7b92_at_posting.google.com>...Received on Thu Jul 18 2002 - 11:10:14 CDT
>
>You can estimate. In reality, it depends also on number of indexes, table
>segments and lots of other things. However, you can safely bet that if you
have
>more than 7 tables in your query, CBO is not gonna give you optimal plan,
ever.
>