Florian Pflug <fgp(at)phlo(dot)org> writes:
> The validity wouldn't change, only the kind of lock taken. If all columns to be locked are part of some unique index, we'd record that fact in the locked tuple's infomask, and thus know that only a certain subset of columns are to be prevented from being updated.
There's not enough space in the infomask to record which columns (or
which unique index) are involved. And if you're talking about data that
could remain on disk long after the unique index is gone, that's not
going to be good enough.
regards, tom lane