OK got it.
Thanks for the help.
Cheers,
Pieter
On 11/02/2017 16:46, Daniel Kuppitz wrote:
> This looks like a bug in 3.2.3. It's clearly expected to fail, since by()
> modulators should always fail if the traverser can't emit a value. What you
> actually want to do is this:
>
> gremlin> g.traversal().V(a1.id()).optional(
> ......1> outE("ab").as("e").otherV().as("vb").optional(
> ......2> outE("bc").as("e").otherV().as("vc"))).
> ......3> order().by(select(first, "e").by("order")).
> ......4> by(select(last, "e").by("order")).values("name")
> ==>b3
> ==>b2
> ==>c3
> ==>c2
> ==>c1
>
> Not related to your problem, but I thought I should point that out: don't
> use otherV() when you know the direction.
>
> g.traversal().V(a1.id()).optional(
> outE("ab").as("e").inV().as("vb").optional(
> outE("bc").as("e").inV().as("vc"))).
> order().by(select(first, "e").by("order")).
> by(select(last, "e").by("order")).values("name")
>
> Also, some labels are redundant in this particular traversal; get rid of
> them:
>
> g.traversal().V(a1.id()).optional(
> outE("ab").as("e").inV().optional(
> outE("bc").as("e").inV())).
> order().by(select(first, "e").by("order")).
> by(select(last, "e").by("order")).values("name")
>
> Oh, and there's something else: The query would fail if there wouldn't be a
> single "ab" edge. If you want to take this into account, do:
>
> g.traversal().V(a1.id()).optional(
> outE("ab").as("e").inV().optional(
> outE("bc").as("e").inV())).
> order().by(coalesce(select(first, "e").by("order"), constant(0))).
> by(coalesce(select(last, "e").by("order"),
> constant(0))).values("name")
>
> And finally, pointing out the obvious: don't create a new traversal source
> for every query.
>
> That's it.
>
> Cheers,
> Daniel
>
>
> On Sat, Feb 11, 2017 at 3:03 PM, pieter-gmail <[email protected]>
> wrote:
>
>> Hi,
>>
>> The following query no longer works on 3.2.4
>>
>> @Test
>> public void testOptionalWithOrderBy() {
>> final TinkerGraph g = TinkerGraph.open();
>> Vertex a1 = g.addVertex(T.label, "A", "name", "a1");
>> Vertex b1 = g.addVertex(T.label, "B", "name", "b1");
>> Vertex b2 = g.addVertex(T.label, "B", "name", "b2");
>> Vertex b3 = g.addVertex(T.label, "B", "name", "b3");
>> Vertex c1 = g.addVertex(T.label, "C", "name", "c1");
>> Vertex c2 = g.addVertex(T.label, "C", "name", "c2");
>> Vertex c3 = g.addVertex(T.label, "C", "name", "c3");
>> a1.addEdge("ab", b1, "order", 3);
>> a1.addEdge("ab", b2, "order", 2);
>> a1.addEdge("ab", b3, "order", 1);
>> b1.addEdge("bc", c1, "order", 3);
>> b1.addEdge("bc", c2, "order", 2);
>> b1.addEdge("bc", c3, "order", 1);
>> GraphTraversal<Vertex, Vertex> traversal = g.traversal().V(a1.id
>> ())
>> .optional(
>> __.outE("ab").as("ab").otherV().as("vb")
>> .optional(
>>
>> __.outE("bc").as("bc").otherV().as("vc")
>> )
>> )
>> .order().by(__.select("ab").by("order"),
>> Order.incr).by(__.select("bc").by("order"), Order.incr);
>> while (traversal.hasNext()) {
>> System.out.println(traversal.next().<String>value("name"));
>> }
>> }
>>
>> On 3.2.3 it returns
>>
>> b3
>> b2
>> c3
>> c2
>> c1
>>
>> On 3.2.4 it throws the following exception,
>>
>> java.lang.IllegalArgumentException: The provided traverser does not map
>> to a value: v[6]->[SelectOneStep(bc,value(order))]
>> at
>> org.apache.tinkerpop.gremlin.process.traversal.util.TraversalUtil.apply(
>> TraversalUtil.java:45)
>> at
>> org.apache.tinkerpop.gremlin.process.traversal.step.map.OrderGlobalStep.
>> createProjectedTraverser(OrderGlobalStep.java:155)
>> at
>> org.apache.tinkerpop.gremlin.process.traversal.step.map.OrderGlobalStep.
>> processAllStarts(OrderGlobalStep.java:74)
>> at
>> org.apache.tinkerpop.gremlin.process.traversal.step.util.
>> CollectingBarrierStep.processNextStart(CollectingBarrierStep.java:108)
>> at
>> org.apache.tinkerpop.gremlin.process.traversal.step.util.
>> AbstractStep.hasNext(AbstractStep.java:143)
>> at
>> org.apache.tinkerpop.gremlin.process.traversal.util.
>> DefaultTraversal.hasNext(DefaultTraversal.java:184)
>>
>> Has the semantics changed or is it a bug?
>>
>> Thanks
>> Pieter
>>
>>
