I disagree with that, Gokul -- if the ordering operators are volatile or just incorrect, during DELETE, you could set xmax in the wrong IndexTuple. Then there will be another IndexTuple that says it's visible, but it points to a non-visible heap tuple. I think you should follow the pointers to the heap before you decide to let an index tuple remain in the index during vacuum. This would ensure that all references from an index to a heap tuple are removed before vacuuming the heap tuple. I would be worried about what might break if this invariant doesn't hold.
Well, Karl, if we have to support function based indexes/IOT, one thing is for sure. We can't support them for volatile functions / broken data types. Everyone agrees with that. But the question is how we identify something is not a volatile function. Only way currently is to let the user make the decision( Or we should consult some mathematician ). So we need not consult the heaptuple.
Gokul.
