Paul Ramsey <pramsey(at)cleverelephant(dot)ca> writes:
> I had what seemed to be working code except for a couple rare cases,
> but when I fixed those cases it turned out that I had a major problem:
> building a <var> OP <const> expression works fine, but building a
> <const> OP <var> expression returns me an error.
Yup, you're not supposed to do that. The output expression *must* have
the index key on the left, it's up to you to commute the operator if
needed to make that happen.
regards, tom lane