Fabio Ugo Venchiarutti <fabio(at)vuole(dot)me> writes:
> As you can see, CONCAT()'s output isn't deemed suitable for an index
> scan. The same happens for all type-compatible STABLE functions i tried.
Conversion of the pattern to an index qualification requires that the
pattern be a plan-time constant. STABLE functions, by definition,
are not that.
regards, tom lane