On Sun, 23 Dec 2018 20:21:22 -0800, Mitar <mmitar@xxxxxxxxx> wrote: >Currently I am doing: > >CREATE TRIGGER some_trigger AFTER UPDATE ON my_table REFERENCING NEW >TABLE AS new_table OLD TABLE AS old_table FOR EACH STATEMENT EXECUTE >FUNCTION my_trigger(); > >In my trigger I do: > >PERFORM * FROM ((TABLE new_table EXCEPT TABLE new_table) UNION ALL >(TABLE new_table EXCEPT TABLE old_table)) AS differences LIMIT 1; >IF FOUND THEN > ... > >But I wonder if there is an easier way. I would just like to know if >an UPDATE really changed anything. > >For DELETE I do "PERFORM * FROM old_table LIMIT 1" and for INSERT I >do "PERFORM * FROM new_table LIMIT 1" and I think this is reasonable. >Still, not sure why I have to store the whole relation just to know if >statement really changed anything. You're still thinking in terms of deltas for the whole table. Think individual rows instead. With a BY ROW trigger, the difference between the NEW and OLD variables lets you see the changes to the particular row. George
