On Apr 5, 7:09 pm, "joel garry" <joel-ga..._at_home.com> wrote:
> On Apr 4, 5:16 pm, "Kevin Kirkpatrick" <kvnkrkpt..._at_gmail.com> wrote:
>
>
>
> > > - have no join clause between kk_small and kk_big, yet you list them
> > > in this order, which is obeyed by CBO.
>
> > Did I just step into the twighlight zone? Syband, this comment makes
> > so little sense that I'm literally stumped as to how to reply. Do you
> > know even know what the CBO is?
>
> > > What else do you expect?
>
> > Certainly not a response from a "Senior Oracle DBA" who thinks that
> > the CBO chooses join order based on the order in which tables are
> > listed in a query...
>
> In the case of tie-breakers, that is, where the optimizer thinks the
> cost is equal for two join orders, RBO worked from last to first, CBO
> works in order written, IIRC.
>
> jg
> --
> @home.com is bogus.http://www.speakeasy.org/~jwilton/oracle/oracle-misconceptions.html
I believe the order of listed tables matters in the rare case where
1) enough tables are used that heuristics are brought into play and
2) two tbles are expected to have the exact same cardinality (the
table-ordering heuristic goes by cardinality first, table-ordering-in-
the-sql second)
Received on Fri Apr 06 2007 - 09:44:20 CDT
