Martijn van Oosterhout <kleptog@svana.org> writes:
> Now, lets say you add a field to the tuple which you the position of
> the index entry. You can only reasonably do this for one index, say the
> primary key. Now you have a two-way link the updating becomes much
> quicker, at the cost of even more overhead.
I think this is fairly infeasible --- consider what it does to the cost
and (lack of) atomicity of an index page split, for instance.
regards, tom lane