In the committed HOT patch, I removed pgstats tracking of dead space,
because the system isn't doing anything with the info and it's not real
clear that the info is of value to DBAs either. However, I did make a
diff of the removal step; if we choose to put back the capability, the
patch would be something close to the attached. Just sticking it in
the archives before I forget (I think I'd fixed a omission or two in
Pavan's original, so this version seems worth archiving).
regards, tom lane