Determining if a table really changed in a trigger

Hi!

I have a trigger like:

CREATE TRIGGER update_trigger AFTER UPDATE ON my_table REFERENCING NEW
TABLE AS new_table OLD TABLE AS old_table FOR EACH STATEMENT EXECUTE
FUNCTION trigger_function;

I would like to test inside trigger_function if the table really
changed. I have tried to do:

PERFORM * FROM ((TABLE old_table EXCEPT TABLE new_table) UNION ALL
(TABLE new_table EXCEPT TABLE old_table)) AS differences LIMIT 1;
IF FOUND THEN
... changed ...
END IF;

But this fails if the table contains a JSON field with the error:

could not identify an equality operator for type json

The table has an unique index column, if that helps.

Mitar

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