help with evaluator

[Javad Karabi]

How would i use the traversal description to do the following?

MATCH me-[:preferred_store]->(:Store)<-[:preferred_store]-(:Member)-[:ordered]->(p:Product)

I assumed that the following worked:

       .relationships( DynamicRelationshipType.withName("preferred_store"), Direction.OUTGOING )

       .relationships( DynamicRelationshipType.withName("preferred_store"), Direction.INCOMING )

       .relationships( DynamicRelationshipType.withName("ordered"), Direction.OUTGOING )

       .relationships( DynamicRelationshipType.withName("product"), Direction.OUTGOING )

However, I am seeing that the order in which relationships() is executed does not make a difference, it just adds the relationships to a global list of allowed relationships for the description... how would i ensure that the traversal only goes from preferred store, to ordered, to the product?

[Michael Hunger]

I think you have to create a custom RelationshipExpander, that takes a list of pairs of type and direction and checks at the current path length for the correct combo to look for.

I think from a quick look that org.neo4j.kernel.OrderedByTypeExpander already does this btw. Please check.

new OrderedByTypeExpander(asList(Pair.of(DynamicRelationshipType.withName("preferred_store"), Direction.OUTGOING),Pair.of( DynamicRelationshipType.withName("preferred_store"), Direction.INCOMING), ....)

Michael

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[Javad Karabi]

the asList can not seem to be found... where is that provided?

[Stefan Armbruster]

Arrays.asList from the JDK,
http://docs.oracle.com/javase/7/docs/api/java/util/Arrays.html#asList(T...)

2014/1/25 Javad Karabi <karab...@gmail.com>:

[Javad Karabi]

it does not seem to work for me

error: cannot find symbol

        asList(

        ^

  symbol:   method asList(Pair<Rels,Direction>)

[Javad Karabi]

scratch that, i forgot to import it...

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[Javad Karabi]

but now, i am seeing that it does traverse ()-[:preferred_store]->()<-[:preferred_store]-()

but, i am seeing that it _again_ traverses out via preferred_store:

(0)--[preferred_store,10]-->(11)<--[preferred_store,3517594]--(90746)--[preferred_store,3517600]-->(19758)

even though my expander looks as such:

      PathExpander e = (new org.neo4j.kernel.OrderedByTypeExpander())

            .add( Rels.preferred_store, Direction.OUTGOING )

            .add( Rels.preferred_store, Direction.INCOMING )

            .add( Rels.ordered, Direction.OUTGOING )

            ;

should this not match only ()-[:preferred_store]->()<-[:preferred_store]-()-[:ordered]->()

?

[Max De Marzi Jr.]

Use your own Array Expander:

           RelationshipType[][] orderedRelTypes = {

                    { Relations.FRIENDS, Relations.ENEMIES },

                    { Relations.LIKES },

                    { Relations.HATES}

            };

            Direction[] directions = {Direction.OUTGOING, Direction.INCOMING, Direction.INCOMING}  ;

            Traverser traverser = Traversal.description()

                    .depthFirst()

                    .expand(new ArrayExpander(directions,orderedRelTypes))

                    .evaluator(Evaluators.atDepth(3))

                    .uniqueness(Uniqueness.NONE)

                    .traverse(person);

public class ArrayExpander implements PathExpander {

    private Direction[] directions;

    private RelationshipType[][] types;

    public ArrayExpander(Direction[] directions, RelationshipType[][] types )

    {

        this.types = types;

        this.directions = directions;

    }

    public Iterable<Relationship> expand(Path path, BranchState state){

        return path.endNode().getRelationships(directions[path.length()],

                types[path.length()]);

    }

    public ArrayExpander reverse()

    {

        return new ArrayExpander(directions, types);

    }

}

[Michael Hunger]

Good point Max,

you're right the OrderedType expander doesn't really do that. Did you have a blog posted about that?

Michael