TG_COLUMNS_UPDATED

I would like another TG_* special variable to be available to a PL/pgSQL trigger-function.

TG_COLUMNS_UPDATED

Its value would be NULL unless: TG_OP == ' UPDATE' and TG_LEVEL == 'ROW'

Data type == varbit
One bit for each column of the table that the trigger is created on.
1 means that the column was in the set clause of the update statement that made the trigger fire
0 means it was not

I understand that CREATE TRIGGER already has
UPDATE [ OF column_name [, ... ] ]

Is this a relatively straightforward enhancement ?

It would allow me to know whether various timestamp columns in the row were
unlucky enough to have been set to the same exact value already existing in the table
*versus* were simply not set by the UPDATE statement.

Thanks,
-dvs-