Joachim Wieland <jwieland@kawo2.rwth-aachen.de> writes:
> So why is a
> SELECT ... FROM table WHERE col = f(...)
> (with a STABLE function f) not a "single table scan"
The point is that the system *may* choose to evaluate f() only once,
not that it *must* do so. The classification exists to make it valid
to use an indexscan on "col".
regards, tom lane