Re: failing optional and order by gremlin
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
> 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 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().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
>>
>>
Re: failing optional and order by gremlin
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
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 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().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
>
>
RE: failing optional and order by gremlin
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 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().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
