Tinkerpop3 Reusing Traversal

[Flavio Cordova]

Consider a situation where I've got to gather some statistics about some vertices in my graph, like that:

Double minutesSpent = g.V()
 .has("type", "Epic").in()
 .has("type", P.without("Bug", "Test Cycle"))
 .until(__.in("TASK_OF").count().is(0)).repeat(__.inE("TASK_OF")
 .outV())
 .values("timeSpent")
 .sum().next();

Long issuesWorked = g.V()
 .has("type", "Epic").in()
 .has("type", P.without("Bug", "Test Cycle"))
 .until(__.in("TASK_OF").count().is(0)).repeat(__.inE("TASK_OF")
 .outV())
 .count();

Long peopleInvolved = g.V()
 .has("type", "Epic").in()
 .has("type", P.without("Bug", "Test Cycle"))
 .until(__.in("TASK_OF").count().is(0)).repeat(__.inE("TASK_OF")
 .outV())
 .out()
 .count();

Notice that part of the traversal code that selects the nodes is always the same, what seems really error-prone.

I've tried to isolate that code in a separated GraphTraversal:

GraphTraversal<Vertex,Vertex> baseQuery = g.V()
 .has("type", "Epic").in()
 .has("type", P.without("Bug", "Test Cycle"))
 .until(__.in("TASK_OF").count().is(0)).repeat(__.inE("TASK_OF")
 .outV());

Double minutesSpent = baseQuery.values("timeSpent").sum().next();
Long issuesWorked = baseQuery.count();
Long peopleInvolved = baeQuery.out().count();

The problem of this approach is that I can't reuse baseQuery because "The traversal strategies are complete and the traversal can no longer be modulated".

I've also thought about creating a subgraph and then work with it, but the problem is that "g" is already a subgraph and apparently I can't create a subgraph from another, narrowing the view.

Is there any different approach that I could use in this case ?

[Daniel Kuppitz]

Hi Flavio,

clone() will be your friend:

gremlin> baseQuery = g.V().hasLabel("person"); q1 = baseQuery.clone().out("knows").path().by("name"); q2 = baseQuery.clone().out("created").path().by("name"); []
gremlin> q1
==>[marko, vadas]
==>[marko, josh]
gremlin> q2
==>[marko, lop]
==>[josh, ripple]
==>[josh, lop]
==>[peter, lop]

Cheers,

Daniel

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[Flavio Cordova]

I've tried Traversal and GraphTraversal and none of them have a clone method.

Am I missing something ? Wrong version, maybe ?

(I'm using 3.01)

[Daniel Kuppitz]

GraphTraversal extends Traversal, which implements Cloneable. That's always been the case:

https://github.com/apache/incubator-tinkerpop/blob/3.0.1-incubating/gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/traversal/Traversal.java#L59

Cheers,

Daniel

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[Flavio Cordova]

Actually, implementing Cloneable only won't make the method public because it's protected on Object class and Cloneable is just a marker interface.

However looking the code I found out that Traversal has an inner interface called Admin and Traversal.Admin does expose the clone method, so the code bellow works just fine:

Traversal t = graph.traversal().V().has("type", "COMPONENT");
Traversal newT = t.asAdmin().clone();

System.out.println("Count1: " + t.count().next());

System.out.println("Count2: " + newT.count().next());