Dimitri Fontaine <dfontaine@hi-media.com> writes:
> Tom Lane <tgl@sss.pgh.pa.us> writes:
>> However, what it *is* associated with is a sort ordering, and the notion
>> that btree opclasses are what define orderings is sufficiently deeply
>> wired into the system that undoing it would be a huge PITA. So unless
>> we can see a pretty clear future need for more information in this
>> category, I'm not really inclined to invent some new structure
>> altogether. I'm just wondering if anyone does see that...
> I think there's the associativity property of operators that we might
> want to have someday, in order for the planner to know some more about
> joins on A = B then on B = C, or replace with < if you will.
We already do know about that, at least in the case of =. The reason it
doesn't do transitive < deductions is not lack of information but doubt
that it's worth the cycles to try.
regards, tom lane