RE: Oracle CBO question

  • From: <Joel.Patterson@xxxxxxxxxxx>
  • To: <contactarul@xxxxxxxxx>
  • Date: Thu, 7 Jun 2007 09:59:09 -0400

Thanks for the replies, I believe I have the proper response.


A research project was not the intention.  If the premise were true, I
would imagine someone on the list would know and could answer
immediately.   The responses indicate for the most part that it is
indeed untrue, and that the developer should verify his source or do
some due diligence before requesting the same from the DBA.   


(although I suspect he thought I knew the answer off the top of my head
as well...).   From the sounds of his questions though, something else
is probably going wrong with his queries.





Joel Patterson 
Database Administrator 
904  727-2546 


From: Arul Ramachandran [mailto:contactarul@xxxxxxxxx] 
Sent: Thursday, June 07, 2007 9:53 AM
To: Patterson, Joel
Cc: oracle-l@xxxxxxxxxxxxx
Subject: Re: Oracle CBO question


I'd like to know where the consultant developer got this information :-)

This can't be true, I've been working on CRM application where most
queries are at the very least 25 way joins. No special CBO settings done
for them. 


On 6/7/07, Joel.Patterson@xxxxxxxxxxx <Joel.Patterson@xxxxxxxxxxx >

I have received a question from a consultant developer - below.   Can
anyone answer?


I was once told that the CBO can only handle a certain number of tables
in a query (16 iirc).  Do you know what the CBO does when there are
more?  Try to optimize based on knowledge of the first 16 tables in the
Where clause? 




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