BTW may I request another test with the attached patch? In this patch, we check if the PageIsFull() even before deciding which attributes to check for modification. If the page is already full, there is hardly any chance of doing a HOT update (there could be a corner case where the new tuple is smaller than the tuple used in previous UPDATE and we have just enough space to do HOT update this time, but I can think that's too narrow).
I would also request you to do a slightly different test where instead of updating the second column, we update the last column of the index i.e. col9. Would really appreciate if you share results with both master and v19 patch.
