ArangoDB: Find last node in path

Question

I'm pretty new to Arangodb and I'm trying to get the last/leaf node (I guess vertex) in a graph. So given I've the following graph:

Now I want start the traversal with 6010142. The query should return 6010625 because it is the last node that can be reached via 6010145. But how does the query looks like?

I already tried:

FOR v, e, p IN 1..5 OUTBOUND {_id: 'nodes/6010142'} GRAPH 'test' RETURN v

But it also returns 6010145. Furthermore it is limited to a maxDepth of 5 but my graph can exceed the limit. So I also need a solution that works for any depth. Hopefully anyone can help me :-)

cheshire cheshire · Accepted Answer · 2020-12-12T01:21:45

I'm also just starting out with AQL but maybe this can help.

FOR v IN 1..5 OUTBOUND {_id: 'nodes/6010142'} GRAPH 'test' OPTIONS {uniqueVertices: 'global', bfs: true}
FILTER LENGTH(FOR vv IN OUTBOUND v GRAPH 'test' LIMIT 1 RETURN 1) == 0  
RETURN v

This approach follows an older ArangoDB cook book (p. 39) for finding leaf nodes. The filter line takes the connected nodes found by the first line and does a second traversal to check if this is actually a leaf.

The OPTIONS {uniqueVertices: 'global', bfs: true} part is an optimization if you are only interested in unique leaf nodes and not all the different paths to those nodes.

Regarding maxDepth I would just use a sufficiently high number. The worst case would be the number of nodes in your graph.

(The graph you posted and your description seem to disagree about the direction of the edges. Maybe you need to use INBOUND.)

ArangoDB: Find last node in path

1 Answers