创建Hive视图

Question

我有一个名为find_distance的Hive UDF，它计算一对lat-long坐标之间的坐标距离。 我还有一个表格，其中包含城市名称列表及其各自的纬度坐标。 所以目前如果我需要找到两个城市之间的距离，比如丹佛和圣何塞，我需要进行自我加入：

Select find_Distance(cityA.latitude, cityA.longitude, cityB.latitude, cityB.longitude) from
(select latitude, longitude from city_data.map_info where city = 'Denver') cityA
join
(select latitude, longitude from city_data.map_info where city = 'San Jose') cityB;

我如何构建一个只接受城市名称作为参数的视图？所以实际上我可以使用

SELECT distance from city_distance where cityA = 'Denver' and cityB = 'San Jose'

Answer 1

试试这个视图：

CREATE VIEW city_distance AS
SELECT
  cityA.city as city_from,
  cityA.city as city_to,
  find_Distance(cityA.latitude, cityA.longitude, cityB.latitude, cityB.longitude) as distance
FROM
  (SELECT city, latitude, longitude FROM city_data.map_info) cityA
  CROSS JOIN
  (SELECT city, latitude, longitude FROM city_data.map_info) cityB;