how can i get Shortest Path cypher query?

Question

I created a Neo4j database with the cypher statement here:https://gist.github.com/neoecos/8748091

i want to know : how to get : 1.less Transfer Paths (order by transfer) 2.the Shortest Path （order by path length) 3.the optimal Path (less Transfer and the Shortest Path)

please give the corresponding query. And do you think that is the best way to create a Bus inquiry system？ Thanks a lot.

Brian Underwood Brian Underwood · Accepted Answer · 2015-10-12T02:19:02

The shortest path is pretty easy:

MATCH path=shortestPath((station_44:STATION {id:44})-[*0..10]-(station_46:STATION {id:46}))
RETURN path

As far as counting transfers you can do something like this:

MATCH path=allShortestPaths((station_44:STATION {id:44})-[rels*0..10]-(station_46:STATION {id:46}))
RETURN length(path) AS stop_count, length(FILTER(index IN RANGE(1, length(rels)-1) WHERE (rels[index]).bus <> (rels[index - 1]).bus)) AS transfer_count

Once you have those two variables you can calculate / sort however you like. For example:

MATCH path=(station_44:STATION {id:44})-[rels*0..4]-(station_46:STATION {id:46})
WITH length(path) AS stop_count, length(FILTER(index IN RANGE(1, length(rels)-1) WHERE (rels[index]).bus <> (rels[index - 1]).bus)) AS transfer_count
RETURN stop_count, transfer_count
ORDER BY (stop_count * 0.5) + (transfer_count * 2.0) DESC

Here I removed the allShortestPaths call so that you get different lengths of paths. The ORDER BY uses weights on the two metrics. Unfortunately, at least in my DB, if you go beyond a path length of four it starts to get really slow. You might be able to improve that by introducing a direction arrow in the path, if that makes sense in your case.

how can i get Shortest Path cypher query?

1 Answers