Re: CBO not using the index even though it is faster when hinted ....

Are any of the columns in the index declared to be NOT NULL - if not, then the hint is invalid because obeying it could produce the wrong answer.

Regards

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

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

-----Original Message-----
To: Multiple recipients of list ORACLE-L <ORACLE-L_at_fatcity.com> Date: 24 January 2003 03:19
....

>Anyone have any problems with the CBO not using
>a index when you know it is faster by forcing a
>hint ?
>
>I have set the following ...
>
>Solaris
>Oracle Version 8.1.7.4
>
>block size = 8
>DB_FILE_MULTIBLOCK_READ_COUNT = 8
>mode = Choose
>
>also using Tim Gormans 90 and 50 values for the other optimizer
parms.
>
>Select col1, col2, col3, blah1, blah2 from table order by col1, col2,
col3;
>
>
>Concatenate index on col1, col2, col3.
>
>

-- 
Please see the official ORACLE-L FAQ: http://www.orafaq.net
-- 
Author: Jonathan Lewis
  INET: jonathan_at_jlcomp.demon.co.uk

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