comparing OLD and NEW in update trigger..

Hi there,

i'm planning to use the following trigger function to update a timestamp of
a row when it is UPDATEd:

CREATE OR REPLACE modified_trigger() RETURNS opaque AS $$
BEGIN
         NEW.modify_timestamp := now();
END;
$$ LANGUAGE SQL;

Since i like to use the same trigger procedure for various tables, i'm
planning to keep it very generic.

What i'd like to do now is to just update the modify_timestamp column if OLD
and NEW are different. I'd LOOP over the row elements, and compare each
column of OLD with NEW, and bailing out if there's a difference.

I'd appreciate your help on the following two questions:

- How can i get the column names of NEW/OLD? Is there a set returning
function for this?
- Is there a more efficient way to compare whole rows?

thanks,

Alex Mayrhofer
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