Waiting for 8.5 – conditional triggers

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.

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