在一个查询中使用PgRouting获得多个最短路径？

12

我想一次在多个源和目标对上运行最短路径算法，并获得结果表，然后对其进行处理。

我该怎么做呢？该查询不起作用：

SELECT a.source, a.target, paths.* 
FROM all_to_all a, shortest_path_astar('...', a.source, a.target, false, false) paths;

ERROR:  function expression in FROM cannot refer to other relations of same query level

（顺便说一句，all_to_all并不是字面意思，:)只是一些随机对。

这也不起作用：

SELECT * 
FROM all_to_all a, (
   SELECT * FROM shortest_path_astar('...', a.source, a.target, false, false) yyy
) AS t2;

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----请您详细说明一下吗？我有同样的问题，但不能正确地获得这些对？（摘自

— 这篇

13

就像是

SELECT 
  source, 
  target,
  (SELECT SUM(cost) FROM  -- or whatever you want to do with the routing result
     (SELECT * FROM shortest_path_astar('...',
       source,
       target,
       false,
       false)
     ) AS foo 
  ) AS cost
FROM all_to_all;

— 暗处
source

4

这是一个查询，它返回所有源-目标组合的所有段：

SELECT
    source,
    target,
    shortest_path_astar('SELECT gid AS id, length AS cost, * FROM ways', source, target, false, false) AS segment
FROM
    all_to_all

难以置信，与SQL语法不一致，但是可以！

source | target | segment
-------+--------+----------------
     1 |      4 | (1, 2, 0.1357)
     1 |      4 | (2, 3, 0.2468)
     1 |      4 | (3, 4, 0.9)
     1 |      4 | (4, -1, 0)
other sources & targets here

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