hamann.w@t-online.de writes:
> Now, in versions 8 and later the "using <&-" is rejected,
> the ordering op "needs to be < or > member of a btree operator class".
> What is needed to create the old behaviour again
> - create a complete operator class, including new names for the unchanged equals/not equals function?
Yes. It sounds like you have pretty much all the spare parts you need,
you just have to collect them together into an opclass for each
ordering you want.
> Is this relevant to performance?
Somewhat, in that it helps the planner optimize ordering considerations.
But IIRC the main argument for tightening it up was to catch mistakes
wherein somebody says "ORDER BY x USING &&", or some other operator that
doesn't produce a consistent sort order.
regards, tom lane