CREATE OR REPLACE FUNCTION public.pd_get_ordernumber(p_user_id integer)
 RETURNS character varying -- user_id - 5 chars, CURRENT day - 8 chars, # FOR CURRENT day - 7 chars
 LANGUAGE plpgsql
AS $function$
DECLARE ret character varying;
DECLARE next_code character varying;
DECLARE i bigint;
DECLARE order_number_exists integer;
DECLARE ret_non_exists_roder integer;

  begin

	ret= concat( lpad( cast( p_user_id AS character varying ), 5, '0'), to_char(current_timestamp,  'YYYYMMDD') );
	ret_non_exists_roder= 0;
	i = 1;
	order_number_exists= 1;
	WHILE ( i< 9999999 AND ret_non_exists_roder = 0 ) LOOP

	   next_code= concat( ret, lpad( cast( i AS character varying ), 7, '0') );

	   SELECT count("id") INTO order_number_exists FROM pd_order WHERE order_number = next_code LIMIT 1;

	   IF order_number_exists = 0 THEN
		  ret_non_exists_roder= i;
	   END IF;

	   i = i+1;

	END LOOP;

	IF ret_non_exists_roder > 0 THEN
	  RETURN concat( ret, lpad( cast( ret_non_exists_roder AS character varying ), 7, '0') );
	END IF;

	RETURN '';
  end
$function$

		$this->db->trans_start();
				...
		$OrderId = $this->morder->UpdateOrder(0, $update_data );
		if ($OrderId) {
			if ($this->db->trans_status() === FALSE) {
				$this->db->trans_rollback();
			} else {
				$this->db->trans_commit();
			}