Including Snapshot Info with Indexes

Hi,
Currently The index implementation in Postgresql does not store the
Snapshot information in the Index. If we add the snapshot information into
the indexing structure, we will have the following advantages.

a) There can be index only scans like Oracle
b) Unique indexes will become less costly, as older index tuples can be
found out.
c) Even the index scans will get faster, since some of the index tuples
won't translate into HeapScans.
d) Deletes and Updates will become slightly costly, as they have to update
these indexes.

I propose we add a DDL like "Create Index .. With Snapshot", which will have
different relkind.

The design in my mind is to add the Snapshot info together with the values
as first variables. We need to change the Index_getattr slightly to have the
relkind as input parameter, based on which we can have an offset.

Please reply back with your comments.

Thanks,
Gokul.