Performance Improvement for Unique Indexes

Hi,
While i was studying the unique index checks very closely, i realized
that what we need is to find out whether the tuple is deleted / not. So say
a tuple is deleted by a transaction, but it is not dead( because of some
long running transaction ), still we can mark a hint bit as deleted and it
will help the subsequent transactions doing the unique checks. As a matter
of fact, it will help the deferred_unique cases, since it will anyway check
the tuples twice, if there is a duplicate.
So we have one bit left in the Index Tuple that can be used as hint bit.
If we are ready to break the disk compatibility, then we can store the size
as a multiple of 8, and we will get three bits free. Any comments?

Thanks,
Gokul.