On Sun, Jan 21, 2007 at 09:39:32AM +0000, Gregory Stark wrote:
> I guess it's tricky since there may be operators which have valid negators and
> commutators but which don't get used by any btree operator class. Does
> Postgres actually make use of the oprcom and oprnegate in that case? Could
> they be used only for such operators to provide values for when they can't be
> automatically deduced?

Sure, they're used whenever you have expressions of the form (CONST OP
VAR) or NOT(VAR OP CONST). This is basic expression simplification that
has little to do with b-trees in general.

You have operators like "contains" and "is contained by" which would be
opposites of eachother, but could never be used in a b-tree class.

Have a nice day,
Martijn van Oosterhout   <kleptog@svana.org>   http://svana.org/kleptog/
> From each according to his ability. To each according to his ability to 
> litigate.

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