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I recently started to work with pgRouting with this osm file

So I used osm2pgRouting to parse the file and load it into the DB.

osm2pgRouting (using the mapconfig_for_pedestrian.xml) work's fine, but when I try to do a Dijkstra all I get is the Empty set.

here is the SQL request I'm using:

SELECT
    *
FROM
    pgr_dijkstra ('SELECT id, source, target, cost, reverse_cost FROM ways',
        3,
        4);

here my environment:

postgres (PostgreSQL) 10.11
pgRouting: 3.0.0 beta
osm2pgrouting Version 2.3.7

can someone give me a direction on what could be the cause of this behaviour?

more information on the exact line I believe I'm using.

|   id | source | target |
+------+--------+--------+
| 5    |   3317 |      4 |
| 3312 |      3 |   3780 |
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9
  • Possible reason for this could be the source(10) and target(11) value you are specifying. They might be the source and target of the same line. When you give a source id (10). It gets that line and selects its target(11) value to find the next line which has that id a source. But in your case your target itself is that line. So the output is null. Try selecting from your table where source = 10. You will find target value of that line is 11.
    – Arun
    Feb 1, 2020 at 10:05
  • turn out that source 10 does not exist but the problem persists with other sources and targets I tried with source 3 (as a target of 3780) and target 4 (has the source of 3317) and I'm still getting an empty set.
    – julia
    Feb 6, 2020 at 9:05
  • 3780 is the id of line segement or its the target column value??
    – Arun
    Feb 7, 2020 at 5:08
  • i edited the question to have more info on the rows.
    – julia
    Feb 7, 2020 at 9:33
  • Possibly then there is no route between your 3(source) and 4(target). If you are sure that there must be route between this two ids. You can try one solution. Create a copy of your data. Now clear your source and target column. And run pgr_createTopology function of pg_routing. This will recalculate the source and target value for your network. And then get the source of id=5 and target of id=3312 and run your pgr_dijkstra with the new source and target value
    – Arun
    Feb 7, 2020 at 12:24

1 Answer 1

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It is the issue with the OSM data. It is not noded properly. So that's why we have issue in generating route out of pg_routing. Work around is to create noded network. You can use pg_routing function pgr_nodeNetwork. 

SELECT pgr_nodeNetwork('route', 0.001, id := 'gid', the_geom:='geom');

It will create a new dataset which will have node at every intersection. And you can use this data set for routing purpose.

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