See
https://github.com/neo4j/neo4j/blob/c72decf5381a0f38132a2493f336ac2dcf7f945f/community/graph-algo/src/test/java/org/neo4j/graphalgo/impl/path/TestShortestPath.java#L224
for a good example of what it does.
On Thursday, December 22, 2016 at 3:24:15 PM UTC-6, Aviran Katz wrote:
>
> Hi all,
> I'm trying to write a procedure that uses Dijkstra's algorithm to find the
> shortest weighted path between two nodes. All nodes in that path should
> have specific properties and values, otherwise the path is invalid, and the
> algorithm should continue searching for the next shortest weighted path.
> I'm trying to tackle this using PathExpanderBuilder.addNodeFilter, as
> follows:
>
> PathExpanderBuilder builder = PathExpanderBuilder.allTypesAndDirections();
> builder.addNodeFilter(
> node -> !node.hasProperty(prop1) ||
> node.getProperty(prop1) instanceof Long &&
> (long) node.getProperty(prop1) < prop1Value
> );
>
>
> When I run the procedure, the filter doesn't take action, and invalid
> paths end up returning in the query result.
> Below is my full procedure code:
>
> public class Demo {
> @Procedure
> @Description("apoc.algo.multiDijkstraWithDefaultWeight(startNode,
> endNode, " +
> "'distance', 10, 'prop1', 2, 'prop2', [100, 200], 'prop3') " +
> " YIELD path, weight - run dijkstra with relationship property
> name as cost function" +
> " and a default weight if the property does not exist")
> public Stream<WeightedPathResult> multiDijkstraWithDefaultWeight(
> @Name("startNode") Node startNode,
> @Name("endNode") Node endNode,
> @Name("weightPropertyName") String weightPropertyName,
> @Name("defaultWeight") double defaultWeight,
> @Name("longPropName") String longPropName,
> @Name("longPropValue") long longPropValue,
> @Name("listPropName") String listPropName,
> @Name("listPropValues") List<Long> listPropValues,
> @Name("boolPropName") String boolPropName) {
>
> PathFinder<WeightedPath> algo = GraphAlgoFactory.dijkstra(
> buildPathExpanderByPermissions(longPropName, longPropValue,
> listPropName, listPropValues, boolPropName),
> (relationship, direction) ->
> convertToDouble(relationship.getProperty(weightPropertyName, defaultWeight))
> );
> return WeightedPathResult.streamWeightedPathResult(startNode,
> endNode, algo);
> }
>
> private double convertToDouble(Object property) {
> if (property instanceof Double)
> return (double) property;
> else if (property instanceof Long)
> return ((Long) property).doubleValue();
> else if (property instanceof Integer)
> return ((Integer) property).doubleValue();
> return 1;
> }
>
> private PathExpander<Object> buildPathExpanderByPermissions(
> String longPropName,
> long longPropValue,
> String listPropName,
> List<Long> listPropValues,
> String boolPropName
> ) {
> PathExpanderBuilder builder =
> PathExpanderBuilder.allTypesAndDirections();
> builder.addNodeFilter(
> node -> !node.hasProperty(longPropName) ||
> node.getProperty(longPropName) instanceof Long &&
> (long) node.getProperty(longPropName) <
> longPropValue
> );
> builder.addNodeFilter(
> node -> {
> try {
> return !node.hasProperty(listPropName) ||
> (boolean) node.getProperty(boolPropName,
> false) ||
> !Collections.disjoint((List<Long>)
> node.getProperty(listPropName), listPropValues);
> }
> catch (Exception e){
> return false;
> }
> }
> );
> return builder.build();
> }
> }
>
>
> Your help is greatly appreciated.
>
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