Ok, afraid I have not had any success yet.
Added the requirement and am working with a B_O_P_S_SE_SL_Traverser now.
This is what I have tried,
@Override
protected Traverser<E> processNextStart() {
while (true) {
if (this.iterator.hasNext()) {
Pair<E, Map<String, Object>> next = this.iterator.next();
E e = next.getLeft();
Map<String, Object> labeledObjects = next.getRight();
this.labels.clear();
this.labels.addAll(labeledObjects.keySet());
for (String label : labeledObjects.keySet()) {
this.head =
this.head.split(labeledObjects.get(label), this);
}
this.labels.clear();
return this.head.split(e, this);
} else {
this.head = this.starts.next();
this.iterator = this.flatMapCustom(this.head);
}
}
}
Calling head.split seems to be the only way to manipulate the path.
I needed to override the getLabels() method return the correct label for
every head.split(...)
This does not work however as the path is never cleared and thus the
edges accumulate. i.e. the second iteration will have the labeled edge
from the first iteration still in the path, the third iteration the
labels from first and second...
Going to see what happens if I make the path mutable for now, and get a
better understanding of how it all fits together.
Thanks
Pieter
On 02/07/2015 01:15, Matt Frantz wrote:
> I wonder if the right thing to do here is to determine whether your
> Traverser already has a legitimate Path, rather than requiring this
> optimized step to require Path unconditionally (or based on properties of
> child steps, of which there are none). By "legitimate Path", I mean a Path
> that is not EmptyPath. That way, you can avoid calling Path.extend unless
> it is necessary.
>
> The harder question (to me) is how to allow a single step to perform
> multiple Path.extend calls. As Pieter points out, you can't set the Path
> of a Traverser. ImmutablePath returns a new Path, but what are you
> supposed to do with it? Do you need to use TraverserGenerator somehow?
> Traverser.Admin.split?
>
> On Wed, Jul 1, 2015 at 12:40 PM, Marko Rodriguez <[email protected]>
> wrote:
>
>> If you need a Traverser that has path information, then you need to
>> specify that you step getRequirements() has PATH in it.
>>
>> See:
>>
>> https://github.com/apache/incubator-tinkerpop/blob/master/gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/traversal/step/map/PathStep.java#L95-L97
>>
>> Though, if your Step is not a TraversalParent, then its just
>> EnumSet.of(PATH).
>>
>> Realize that path computations are expensive so if you can be selective
>> about when to turn them on or off you will be better off. For instance, see:
>>
>>
>> https://github.com/apache/incubator-tinkerpop/blob/master/gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/traversal/step/map/SelectStep.java#L114-L118
>>
>> HTH,
>> Marko.
>>
>> http://markorodriguez.com
>>
>> On Jul 1, 2015, at 1:19 PM, pieter-gmail <[email protected]> wrote:
>>
>>> I got as far as looking at Path.extend(). It returns the extended path
>>> but I do not know how to set the traverser's path to the new extended
>>> one. There is no setPath(path).
>>>
>>> Looking at split and clone now to see whats possible.
>>>
>>> Currently when select() fires there is only a EmptyPath.
>>>
>>> However I notice when optimized the traverser is B_O_S_SE_SL_Traverser
>>> and when un-optimize it is B_O_P_S_SE_SL_Traverser
>>>
>>> Not quite sure where this difference is coming from.
>>>
>>> Thanks
>>> Pieter
>>>
>>> On 01/07/2015 20:47, Marko Rodriguez wrote:
>>>> Hi,
>>>>
>>>> You then just need to add the edge to the path which is done with
>> Path.extend().
>>>> Is it not working as you expect?
>>>>
>>>> Marko.
>>>>
>>>> http://markorodriguez.com
>>>>
>>>> On Jul 1, 2015, at 12:39 PM, pieter-gmail <[email protected]>
>> wrote:
>>>>> To explain what I am doing from a sql point of view is as follows.
>>>>>
>>>>> If un-optimized, I first execute a query to return the "outB" edges,
>>>>> then for each edge I execute another query the retrieve the inV().
>>>>>
>>>>> The optimization is to makes this happen in one query. Reducing round
>>>>> trips has order of magnitude performance benefits for sqlg.
>>>>>
>>>>> When I do not collapse the steps into one I see that the .select("e",
>>>>> "B") part happens in SelectStep.map where the labeled object is
>>>>> retrieved from Path.objects() where the object was saved as it was
>>>>> touched by the traverser.
>>>>>
>>>>> Now that I have collapsed the steps there is no place where the edge is
>>>>> traversed and stored on the path.
>>>>> Instead I retrieve the labeled edges and the vertices all in one step.
>>>>>
>>>>> At the "//what to do" part I have all the information (The final inV()
>>>>> vertex and a map of the labeled edges) but I need to make it such that
>>>>> the select step will be able to find the labeled edges on the path. In
>>>>> this example the labeled map contains only the edge with "e" as the
>> key.
>>>>> Hope it makes some sense.
>>>>>
>>>>> Thanks
>>>>> Pieter
>>>>>
>>>>> On 01/07/2015 20:02, Marko Rodriguez wrote:
>>>>>> Hi,
>>>>>>
>>>>>> I don't quite understand what you are trying to accomplish (attention
>> span of a tootsie fly), but here are some notes:
>>>>>> 1. Look at AbstractStep.prepareTraveserForNextStep()
>>>>>> 2. B_O_…Traverser specify the requirements that the Traverser
>> satisfies:
>>>>>> B_O_P_S_SE_SL_Traverser =
>> Bulk+Object+Path+Sack+SideEffect+SingleLoop. In other words, a very meaty
>> traverser, indeed.
>>>>>> What do you want "// What to do?" to do?
>>>>>>
>>>>>> Marko.
>>>>>>
>>>>>> http://markorodriguez.com
>>>>>>
>>>>>> On Jul 1, 2015, at 11:32 AM, pieter-gmail <[email protected]>
>> wrote:
>>>>>>> Hi,
>>>>>>>
>>>>>>> I am trying to optimize queries with 'as' in it.
>>>>>>>
>>>>>>> Currently I can optimize consecutive VertexStep and EdgeVertexStep
>>>>>>> (without labels) by combining them into one step.
>>>>>>>
>>>>>>> Now I am trying to achieve the same but with 'as' in the traversal.
>>>>>>>
>>>>>>> e.g.
>>>>>>>
>>>>>>> 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");
>>>>>>> Edge e1 = a1.addEdge("outB", b1);
>>>>>>> Edge e2 = a1.addEdge("outB", b2);
>>>>>>>
>>>>>>> g.tx().commit();
>>>>>>>
>>>>>>> GraphTraversal<Vertex, Map<String, Element>> traversal =
>> g.traversal()
>>>>>>> .V(a1)
>>>>>>> .outE("outB")
>>>>>>> .as("e")
>>>>>>> .inV()
>>>>>>> .as("B")
>>>>>>> .select("e", "B");
>>>>>>>
>>>>>>> I combine all consecutive VertexStep, EdgeVertexStep into one step,
>>>>>>> execute one query and with the result I can construct the labeled
>> edge
>>>>>>> ("e") and vertices ("B").
>>>>>>>
>>>>>>> So far in the combined step I have all the information, but alas
>> what now?
>>>>>>> public class SqlgVertexStepCompiled<S extends SqlgElement, E extends
>>>>>>> SqlgElement> extends FlatMapStep<S, E> {
>>>>>>>
>>>>>>> ...
>>>>>>>
>>>>>>> @Override
>>>>>>> protected Traverser<E> processNextStart() {
>>>>>>> while (true) {
>>>>>>> if (this.iterator.hasNext()) {
>>>>>>> Pair<E, Map<String, Object>> next = this.iterator.next();
>>>>>>> E e = next.getLeft();
>>>>>>> Map<String, Object> labeledObjects = next.getRight();
>>>>>>> for (String label : labeledObjects.keySet()) {
>>>>>>> //What to do
>>>>>>> this.head.path().extend(labeledObjects.get(label),
>> label);
>>>>>>> }
>>>>>>> return this.head.split(e, this);
>>>>>>> } else {
>>>>>>> this.head = this.starts.next();
>>>>>>> this.iterator = this.flatMapCustom(this.head);
>>>>>>> }
>>>>>>> }
>>>>>>> }
>>>>>>>
>>>>>>> ...
>>>>>>>
>>>>>>> Any pointers?
>>>>>>>
>>>>>>> btw, what does all those strange traverser names mean,
>>>>>>> B_O_P_S_SE_SL_Traverser...
>>>>>>>
>>>>>>> Thanks
>>>>>>> Pieter
>>
