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Regards
Jonathan Lewis
http://www.jlcomp.demon.co.uk
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who can answer the questions, but the
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The Co-operative Oracle Users' FAQ
http://www.jlcomp.demon.co.uk/faq/ind_faq.html
"Mark D Powell" <Mark.Powell_at_eds.com> wrote in message
news:2687bb95.0309201634.79e14a35_at_posting.google.com...
> Joe, what version of Oracle did you do your testing on. In the past
> from version 7 and up and including 8.1.7.4 I have observed
optimizer
> plan changes from rearranging my queries.
This is possible, but statistically a little unlikely when using
only three tables. But arithmetical errors in earlier versions of
the optimizer would increase the chances of the problem
showing up.
In a 'tie-break' for the first join order, Oracle will use the order
of the tables in the FROM list. When examining join orders,
the latest join order is only accepted if it is BETTER than
the previous best. So if you get a join cost on N tables
which is the same, then the one that came later
in the permutation list will be ignored - but its position
in the list (the point at which is gets examined) is determined
by the first join order, which is (as noted above) affected by
the original FROM clause order.
Received on Sun Sep 21 2003 - 08:25:23 CDT
