Question

I’m trying to accomplish vertex-wise subgraph matching using the following construct:

a = g.v(1) 
p = g.v(5) 

a.filter{it.map() == p.map()}.out.sideEffect{p = p.out}.loop(3){it.object != null}

I should say that the map comparison surprisingly works well enough, but the side effect part does not seem to modify the p-vertex in a proper way. When I print p after performing these Gremlin steps – it looks like a pipeline. But more explicit p = g.v(p.out.id), p = g.v(p.outE.inV.id) and even numeric i++ side effects do not seem to modify the value at all.

I tried this both in Neo4j Gremlin shell, and through Groovy.

Answer 1

If you get a pipeline when you expect something else, try a next() to see if that gets you what you want. Note that when I next() in the sideEffect closure, x changes.

gremlin> g = TinkerGraphFactory.createTinkerGraph()
==>tinkergraph[vertices:6 edges:6]
gremlin> x = g.v(1)
==>v[1]
gremlin> g.V.out.sideEffect{x = x.out.next()}   
==>v[2]
gremlin> x
==>v[2]