下面是我为间隔2分钟创建的代码

select ways.the_geom from                     
(WITH distance_query AS (
  SELECT *, 
         (length / 1000) / (30 / 3600) AS time_in_seconds
  FROM ways
)
SELECT * FROM 
pgr_drivingDistance('SELECT gid as id, 
                     source, target, 
                     cost FROM ways',
                    2338,
                    120)) as route 
left outer join ways ways 
  on ways.gid = route.edge

问题是，当我把秒（间隔）从120改成300时，我总是得到同样的结果，如果有人能帮助我，我将非常感激！