Since commit e94568ec, the answer is
always "false", and we do not need to complicate the API by arranging
to return a constant value.

Peter Geoghegan

Discussion: http://postgr.es/m/CAM3SWZQWZZ_N=DmmL7tKy_OUjGH_5mN=N=A6h7kHyyDvEhg2DA@mail.gmail.com