Re: Why the monstrous SORT?

• Original Message ----- From: <oracle-l-bounce_at_freelists.org> To: <oracle-l_at_freelists.org> Cc: "Vlad Sadilovskiy" <vlovsky_at_gmail.com> Sent: Tuesday, July 12, 2005 12:58 AM Subject: RE: Why the monstrous SORT?

AND NOT upper(a.item_no) LIKE 'AF-%'

      AND NOT upper(a.item_no) LIKE 'IFF%'

I wasn't aware until now that when applying functions in the predicate like this the CBO (apparently) uses a default

selectivity of only 1%.
                        ^^^^^^

This depends on the nature of the predicate. In the case of

    AND NOT upper(a.item_no) LIKE 'AF-%' I think you'll find it's 5%

As far as I know it's only

    function(colx) = const
that gets 1%

Regards

Jonathan Lewis

Now waiting on the publishers: Cost Based Oracle - Volume 1

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

http://www.jlcomp.demon.co.uk/appearances.html Public Appearances - schedule updated 8th July 2005

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http://www.freelists.org/webpage/oracle-l Received on Tue Jul 12 2005 - 03:39:21 CDT