On 25th of January, Tom Lane committed patch: Implement ALTER TABLE ADD UNIQUE/PRIMARY KEY USING INDEX.   This feature allows a unique or pkey constraint to be created using an already-existing unique index. While the constraint isn't very functionally different from the bare index, ...

Yesterday (August, 7th), Tom Lane committed: Log Message: ----------- Recognize functional dependency on primary keys. This allows a table's other columns to be referenced without listing them in GROUP BY, so long as the primary key column(s) are listed in GROUP BY.   Eventually we should ...

On 29th of July ( I know, there is a long backlog in waiting for 8.5 series. I'm working on it :), Tom Lane committed patch by Dean Rasheed: Support deferrable uniqueness constraints.   The current implementation fires an AFTER ROW trigger for ...