Como registrar a alteração de dados no postgresql?

Função de gatilho muito genérica, encontrada em:https://www. cybertec-postgresql.com/en/tracking-changes-in-postgresql/

Tabela para armazenar o histórico:

CREATE SCHEMA logging;
CREATE TABLE logging.t_history (
        id             serial,
        tstamp         timestamp DEFAULT now(),
        schemaname     text,
        tabname        text,
        operation      text,
        who            text DEFAULT current_user,
        new_val        json,
        old_val        json
);

O gatilho:

CREATE FUNCTION change_trigger() RETURNS trigger AS $$
       BEGIN
         IF TG_OP = 'INSERT'
         THEN INSERT INTO logging.t_history (
                tabname, schemaname, operation, new_val
              ) VALUES (
                TG_RELNAME, TG_TABLE_SCHEMA, TG_OP, row_to_json(NEW)
              );
           RETURN NEW;
         ELSIF  TG_OP = 'UPDATE'
         THEN
           INSERT INTO logging.t_history (
             tabname, schemaname, operation, new_val, old_val
           )
           VALUES (TG_RELNAME, TG_TABLE_SCHEMA, TG_OP, row_to_json(NEW), row_to_json(OLD));
           RETURN NEW;
         ELSIF TG_OP = 'DELETE'
         THEN
           INSERT INTO logging.t_history
             (tabname, schemaname, operation, old_val)
             VALUES (
               TG_RELNAME, TG_TABLE_SCHEMA, TG_OP, row_to_json(OLD)
             );
             RETURN OLD;
         END IF;
       END;
$$ LANGUAGE 'plpgsql' SECURITY DEFINER;

Aplique o gatilho:

CREATE TRIGGER t BEFORE INSERT OR UPDATE OR DELETE ON your_table
        FOR EACH ROW EXECUTE PROCEDURE change_trigger();