code: func Tintervalrel(db XODB, v0 pgtypes.Tinterval) (pgtypes.Reltime, error) {
  	var err error
  
  	// sql query
  	const sqlstr = `SELECT pg_catalog.tintervalrel($1)`
  
  	// run query
  	var ret pgtypes.Reltime
  	XOLog(sqlstr, v0)
  	err = db.QueryRow(sqlstr, v0).Scan(&ret)
  	if err != nil {
  		return pgtypes.Reltime{}, err
  	}
  
  	return ret, nil
  }
docs: // Tintervalrel calls the stored procedure 'pg_catalog.tintervalrel(tinterval) reltime' on db.