ArangoDB中的联接遍历对象结果

Question

I am using ArangoDB's traversal object in order to traverse a recursive group membership structure while avoiding following cycles. There are cases where I need to join the results of two separate traversals. Is there an efficient way to leverage AQL to join the traversal results? I'm currently joining the results in memory with javascript.

Answer 1

I'd like to explain this using the traversal graph . We do two traversals in ANY direction, so the number of results is a little bigger. We start it at points that have neighbors in common which will become the result of the join operation. One query will look at A and E which should have B in common, but others of the iteration not.

The basic iteration:

FOR v IN 1..1 ANY 'circles/A' GRAPH 'traversalGraph' RETURN v._key

Starting from circles/A this results in ["B","G"] , starting from circles/E this results in ["F", "B"] - so its obvious, we should only get "B" as the result of the join.

Our first possible approach is to use two sub queries and join them using INTERSECTION :

LET firstTraversal = (FOR v IN 1..1 ANY 'circles/A' GRAPH 'traversalGraph' RETURN v)
LET secondTraversal = (FOR v IN 1..1 ANY 'circles/E' GRAPH 'traversalGraph' RETURN v)
RETURN INTERSECTION(firstTraversal, secondTraversal)

A possible problem here could be, that a full depth comparison of the objects will be done, which may become expensive. Another approach therefore could be to join them using their _key attribute:

LET firstTraversal = (FOR v IN 1..1 ANY 'circles/A' GRAPH 'traversalGraph' RETURN v)
LET secondTraversal = (FOR v IN 1..1 ANY 'circles/E' GRAPH 'traversalGraph' RETURN v)
FOR oneSet IN firstTraversal
  FOR otherSet IN secondTraversal
    FILTER oneSet._key == otherSet._key RETURN oneSet