add_audit_table

CREATE FUNCTION audit_create_log_tables(_relname text) RETURNS void
    AS $_$
BEGIN
-- TODO log primary key changes
  EXECUTE 
	'CREATE TABLE ' || _RELNAME || '_version_log' ||
	'(	change_id int not null primary key references action_log on delete restrict,
		LIKE ' || _RELNAME || ')';
		
  EXECUTE 'CREATE FUNCTION ' || _RELNAME || '_track_changes() RETURNS TRIGGER AS $ac$
BEGIN
	IF    TG_OP = \'INSERT\' THEN
		INSERT INTO ' || _RELNAME || '_version_log' ||
			' SELECT audit_log_action(\'' || _RELNAME || '\', \'I\'), NEW.*;
		RETURN NEW;
	ELSIF TG_OP = \'UPDATE\' THEN
		INSERT INTO ' || _RELNAME || '_version_log' ||
			' SELECT audit_log_action(\'' || _RELNAME || '\', \'U\'), NEW.*;
		RETURN NEW;
	ELSIF TG_OP = \'DELETE\' THEN
		INSERT INTO ' || _RELNAME || '_version_log' ||
			' SELECT audit_log_action(\'' || _RELNAME || '\', \'D\'), OLD.*;
		RETURN OLD;
	END IF;
	RETURN NEW;
END$ac$ LANGUAGE \'plpgsql\' ';
RETURN;
END$_$
    LANGUAGE plpgsql;




CREATE FUNCTION audit_drop_log_data(_relname text) RETURNS void
    AS $$
BEGIN
	EXECUTE 'DROP TABLE ' || _RELNAME || '_version_log CASCADE';
	EXECUTE 'DROP FUNCTION ' || _RELNAME || '_track_changes() CASCADE' ;
	RETURN;
END$$
    LANGUAGE plpgsql;



CREATE FUNCTION audit_log_action(_relname text, _opname text) RETURNS integer
    AS $$
DECLARE _change_id INT;
	_user_rec  RECORD; 
BEGIN
	_change_id := nextval('action_log_seq');
	SELECT INTO _user_rec  * FROM audited_user;
	INSERT INTO action_log (change_id, party_id, req_host, change_date, rel_name, op_type)
	    VALUES (_change_id, _user_rec.party_id, _user_rec.req_host, now(), _relname, _opname);

	RETURN _change_id;
END $$
    LANGUAGE plpgsql;


CREATE FUNCTION audit_start_log_data(_relname text) RETURNS void
    AS $$
BEGIN
  EXECUTE 'CREATE TRIGGER ' || REPLACE(_relname,'.','_') ||  '_chg_trck_trg AFTER INSERT OR UPDATE OR DELETE ' || 
          ' ON ' || _relname || ' FOR EACH ROW EXECUTE PROCEDURE ' || _relname || '_track_changes()';
  RETURN;
END$$
    LANGUAGE plpgsql;


CREATE FUNCTION audit_stop_log_data(_relname text) RETURNS void
    AS $$
BEGIN
  EXECUTE 'DROP TRIGGER ' || REPLACE(_relname,'.','_') ||  '_chg_trck_trg ON  ' || _relname ;
  RETURN;
END$$
    LANGUAGE plpgsql;