Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org> writes:
> Yes, but how can you tell by looking at the explain? I think the point
> is that the "fraction that would be skipped" should be reported somehow.
It is: it's directly reflected in the startup cost. Previously, a
mergejoin would always have startup cost equal to the sum of its
input startup costs (hence, zero in the cases of interest here).
regards, tom lane