Re: Hints

From: <Laimutis.Nedzinskas_at_seb.lt>
Date: Thu, 18 Aug 2011 11:17:27 +0300
Message-ID: <OF5E5AB575.C69E9AE1-ONC22578F0.002D5BF5-C22578F0.002D8B98_at_seb.lt>

Right. Thank you.
transformations - yes, those are something which can be characterized as a creative part of the optimizer design :)

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  From:       Greg Rahn <greg_at_structureddata.org>                                                                                                     
                                                                                                                                                      
  To:         Laimutis.Nedzinskas_at_seb.lt                                                                                                              
                                                                                                                                                      
  Cc:         oracle-l_at_freelists.org                                                                                                                  
                                                                                                                                                      
  Date:       2011.08.18 11:01                                                                                                                        
                                                                                                                                                      
  Subject:    Re: Hints                                                                                                                               
                                                                                                                                                      

Having FKs allows for table elimination transformations: http://blogs.oracle.com/optimizer/entry/why_are_some_of_the_tables_in_my_query_missing_from_the_plan

2011/8/17 <Laimutis.Nedzinskas_at_seb.lt>:
> As for optimizer and foreign keys then it considers only uniqueness.
> F-keys have no effect on CBO whatsoever. Correct me if I am wrong.

--
Regards,
Greg Rahn
http://structureddata.org



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Received on Thu Aug 18 2011 - 03:17:27 CDT