> which is much closer to the actual number of rows removed by the index
> recheck + the one left.
Is it better to be closer? We are saying those are the "actual"
values not the estimates. If we cannot provide the actual rows, I
think it is better to provide nothing. Something closer to the
reality would create more confusion. Maybe, we just just return the
number of blocks, and put somewhere a note about it. The actual row
count is already available on the upper part of the plan.
By the way, the estimation is a bigger problem than that. Please see
my patch [1] about it.
[1] http://www.postgresql.org/message-id/CAE2gYzzJvzPy-1cSgZjJyH69izSa13SEgFC4i4r2z0qBQ2P8Uw@mail.gmail.com