pgr_dijkstra returns 空集

Question

我正在尝试编写一个函数，该函数能够使用 pgr_dijkstra 函数找到两点之间的最短路线。我正在关注 this guide. With data provided in the guide everything works fine. But when I try to apply the same steps (build a topology using pgr_createTopology and then test it with pgr_dijkstra) to another data set、pgr_dijkstra returns 一个空结果。我还注意到指南的数据集有一个 LineString 几何列，而我有一个 MultiLineString 几何列。可能是什么原因？

我的table的结构：

                                        Table "public.roads"
 Column |              Type              | Collation | Nullable |              Default
--------+--------------------------------+-----------+----------+------------------------------------  
 id     | integer                        |           | not null | nextval('roads_gid_seq'::regclass)
 geom   | geometry(MultiLineString,4326) |           |          |
 source | integer                        |           |          |
 target | integer                        |           |          |
Indexes:
    "roads_pkey" PRIMARY KEY, btree (id)
    "roads_geom_idx" gist (geom)
    "roads_source_idx" btree (source)
    "roads_target_idx" btree (target)

拓扑创建查询：

SELECT pgr_createTopology('roads', 0.00001, 'geom', 'id');

最短路线测试：

SELECT seq, node, edge, cost as cost, agg_cost, geom
FROM pgr_dijkstra(
   'SELECT id, source, target, st_length(geom, true) AS cost FROM roads',
   -- Some random points
   1, 200
) AS pt
JOIN roads rd ON pt.edge = rd.id;

Answer 1

问题实际上与几何数据类型有关。该函数不能与 MultiLineString 一起正常工作，尽管它不会产生任何错误。所以，我已经将 MultiLineString 转换为 LineString，现在一切似乎都正常了。

pgr_dijkstra returns 空集

pgr_dijkstra returns an empty set

postgresql

postgis

pgrouting