"PostgreSQL Bugs List" <pgsql-bugs(at)postgresql(dot)org> writes:
> for the next version of postgresql i would like to see support for 1-byte
> integers (signed and unsigned) and also for 4-bit (1/2-byte) integers
> (signed and unsigned).
See the "char" type (not to be confused with char(n)) and the bitstring
type. There are never going to be sub-byte-sized columns in Postgres;
it just doesn't fit into our storage management model.
regards, tom lane