Comments in-line.
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Jonathan Lewis
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The Co-operative Oracle Users' FAQ
http://www.jlcomp.demon.co.uk/faq/ind_faq.html
"Noons" <wizofoz2k_at_yahoo.com.au> wrote in message
news:3f6cecca$0$23150$afc38c87_at_news.optusnet.com.au...
> Even in the RBO-only days.
> The order of predicates in the "where" clause was not significant.
> It might have been in a point release somewhere, but that most
surely
> would not have lasted long as it would break just about any code
> written prior to it.
It is quite easy with a single table query to switch between
the correct answer and a query failure (i.e. Oracle error) by
switching the order of predicates - both in RBO and CBO.
But it does require bad design in the first place, followed
by queries that then have to use type-coercion inappropriately
>
> Now, IF you want to write your statements in a defensive fashion so
> that they will work well with ot without the CBO (in case the user
has
> CBO on but no stats), there MAY be a case for writing them using the
old
> RBO rules.
>
Not really - RBO works from bottom to top, CBO works from
top to bottom as far as 'tie-breaks' on join orders go.
Received on Sun Sep 21 2003 - 08:13:46 CDT
