Re: Allow to specify #columns in heap/index_form_tuple

I don't see why you'd necessarily need to know where in the index the tuple came from under my proposal. Besides, as I already pointed out, we already hard code minus infinity handling within internal pages during tuple comparisons. 

Anastasia's patch could modify nbtree in exactly the same way as suffix truncation would. I see no conflict there. Quite the opposite, in fact.