Stephan Szabo <sszabo(at)megazone(dot)bigpanda(dot)com> writes:
> I'm wondering if the function under = is an SQL function being inlined.
Bingo --- that's surely it. After inlining, the expression would no
longer look like it matched the index.
You don't want to use SQL functions to define indexable operators
anyway. They leak memory, and are slow, and neither of those are
good properties for an index support function.
regards, tom lane