On 28th of June, Simon Riggs committed patch:
ALTER TABLE ... ALTER CONSTRAINT for FKs Allow constraint attributes to be altered, so the default setting of NOT DEFERRABLE can be altered to DEFERRABLE and back. Review by Abhijit Menon-Sen
Continue reading Waiting for 9.4 – ALTER TABLE … ALTER CONSTRAINT for FKs
On 20th of November Tom Lane committed patch by Takahiro Itagaki which adds interesting functionality:
ADD a WHEN clause TO CREATE TRIGGER, allowing a BOOLEAN expression TO be checked TO determine whether the TRIGGER should be fired. FOR BEFORE triggers this IS mostly a matter OF spec compliance; but FOR AFTER triggers it can provide a noticeable performance improvement, since queuing OF a DEFERRED TRIGGER event AND re-fetching OF the ROW(s) at END OF statement can be short-circuited IF the TRIGGER does NOT need TO be fired. Takahiro Itagaki, reviewed BY KaiGai Kohei.
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 each tuple that looks like it might be non-unique according to the index contents at the time of insertion. This works well as long as there aren't many conflicts, but won't scale to massive unique-key reassignments. Improving that case is a TODO item. Dean Rasheed