How to remove cyclic vertex list from list of outer vertexes

Question

I am new in dse graph, I want to create gremlin query which gives me list of all vertex which is linked from specified vertex but from this list I want to remove those list which are linked cyclic.

e.g.

A --> B
A --> C
A --> D
B --> A

If I have above relation then I want below vertex list as result

[C,D]

B and A should not be in above list as it has cyclic relation

I have below two separate query to find all linked vertexes and to find cyclic vertex

g.V().has('id','id').as('mainV').outE('Prerequisite').inV();

g.V().has('id','id').as('mainV').out().out().cyclicPath().path().unfold().dedup();

Could you please help me to find exact query to achieve my requirement.

Answer 1

So you basically want to filter out vertices, that have an in and an out edge to a particular vertex.

This is your sample graph:

gremlin> g = TinkerGraph.open().traversal()
==>graphtraversalsource[tinkergraph[vertices:0 edges:0], standard]
gremlin> g.addV().property(id, "A").as("a").
......1>   addV().property(id, "B").as("b").
......2>   addV().property(id, "C").as("c").
......3>   addV().property(id, "D").as("d").
......4>   addE("link").from("a").to("b").
......5>   addE("link").from("a").to("c").
......6>   addE("link").from("a").to("d").
......7>   addE("link").from("b").to("a").iterate()

And this is the traversal you're looking for:

gremlin> g.V().as("a").not(out().out().where(eq("a"))).not(__.in().in().where(eq("a")))
==>v[C]
==>v[D]

Answer 2

It sounds like you want to use SimplePath. Please see here for documentation - http://tinkerpop.apache.org/docs/current/reference/#simplepath-step