> I would be nice to get a feel for how much performance loss would be incurred in
> maintaining the index flags against possible performance gains for getting the data back
> out again.
I guess the real question is, why maintain index flags and not simply
drop the index entry altogether?
A more interesting case would be to have the backend process record
index tuples that it would invalidate (if committed), then on commit
send that list to a garbage collection process.
It's still vacuum -- just the reaction time for it would be much
quicker.