ArangoDB Traversal with conditions on vertice's neighbours

Question

I have the following graph:

I'd like to write a AQL query that returns paths, starting from the node Q1 , in which the second node in the path has the neighbour P6 (neighbours of the start node Q1 always have a P-node ( P6 , P4 , ..) in its neighbourhood).

For example, the good paths are : Q1->Q1-P6-3->STRING-2 , Q1->Q1-P6-3->Q1-P6-3-QUAL-P2-2->QUANT-2 , etc. What is the best way to check the condition? For now, I've added to nodes such as Q1-P6-3 an attribute property with the key of P-node from its neighbourhood and just filter paths:

FILTER p.vertices[1].property == 'P6'

But I believe there is a smarter way to do that. Thank you in advance!

Answer 1

The AQL first gets the list of all nodes that have P6 as a direct neighbor and then uses that to filter the paths in the traversal query. This way you do not need to keep track of the property in the vertices:

LET p6Neighbors = (FOR t IN testEdge
                    FILTER t._to == 'test2/P6'
                    RETURN t._from)
for v,e,p in 1..5 ANY 'test2/Q1' testEdge
FILTER p.vertices[1]._id in p6Neighbors
return p