ArangoDB-如何查找与特定节点无关的节点？

Question

For clarity purpose, step names are used as identifiers

I have the following Directed Acyclic Graph (DAG):

What I'm trying to do is select a node, and find all the other nodes that are not connected directly to the selected one, only in an outbound direction.

For example: if I select "root step", my query should only return "test step 3", since it is the only one not connected directly to "root step".

However , if I select "test step 2", it should only return "test step 3", and not "test step", because "test step* is at the same level that "test step 2" is.

For now, here is how I do:

I store, in every "step", the list of parents it has as an array. (test step has ["root step"], etc.)

My query is as follows ( for test step 2 as an example ):

FOR v, e IN 0..10 OUTBOUND "steps/test step 2" steps_relations
    FILTER e._from != "steps/test step 2"
    FILTER e._to != "steps/test step 2"
    FILTER v._id != "steps/test step 2"
    FILTER ["root step"] NONE IN v.parents
RETURN {id: v._key, name: v.name }

For now it returns an empty result instead of the expected ("test step 3"). Any help is greatly appreciated

Answer 1

I have finally managed to fix this. Here is how I did it:

first, I added two fields to each one of my "steps" document:

• root: equals true when it is the root of the tree (like "root step"). Otherwise it simply references the internal ID of the root step

• depth: equals to 0 for the root step, but is incremented. When I add a step to another, the new step's depth equals (parent + 1) ONLY if the result is bigger than the one actually stored.

Once I have this, my query looks as follows:

Situation: I want to list all the steps that can be linked to "test step 2"

FOR step, relation IN 0..10 ANY "steps/root step" steps_relations
    FILTER step.depth > 1 /* THE DEPTH OF test step 2 WICH IS 1 */
    FILTER relation._from != "steps/test step 2" 
RETURN item

This returns successfully "test step 3"

Answer 2

You should rather use the min attribute to suppress edges directly connected:

FOR v, e IN 2..10 OUTBOUND "steps/test step 2" steps_relations
  RETURN {id: v._key, name: v.name }

this way you will only get paths longer than one edge-hop, and the vertices from 2 onwards.