Fixes #2402: See if we can make the aStar algorithm support spatial p…

…oints (#2589) (#2786)

Co-authored-by: Giuseppe Villani <[email protected]>

core/src/main/java/apoc/algo/PathFinding.java

@@ -11,6 +11,7 @@
 import org.neo4j.procedure.Description;
 import org.neo4j.procedure.Name;
 import org.neo4j.procedure.Procedure;
+import org.neo4j.values.storable.PointValue;
 
 import java.util.Collections;
 import java.util.Map;
@@ -19,6 +20,54 @@
 
 public class PathFinding {
 
+    public static class GeoEstimateEvaluatorPointCustom implements EstimateEvaluator<Double> {
+
+        // -- from org.neo4j.graphalgo.impl.util.GeoEstimateEvaluator
+        private static final double EARTH_RADIUS = 6371 * 1000; // Meters
+        private Node cachedGoal;
+        private final String pointPropertyKey;
+        private double[] cachedGoalCoordinates;
+
+        public GeoEstimateEvaluatorPointCustom(String pointPropertyKey) {
+            this.pointPropertyKey = pointPropertyKey;
+        }
+
+        @Override
+        public Double getCost( Node node, Node goal) {
+            double[] nodeCoordinates = getCoordinates(node);
+            if ( cachedGoal == null || !cachedGoal.equals( goal ) )
+            {
+                cachedGoalCoordinates = getCoordinates(goal);
+                cachedGoal = goal;
+            }
+            return distance(nodeCoordinates[0], nodeCoordinates[1],
+                    cachedGoalCoordinates[0], cachedGoalCoordinates[1] );
+        }
+
+        private static double distance( double latitude1, double longitude1,
+                                        double latitude2, double longitude2 ) {
+            latitude1 = Math.toRadians( latitude1 );
+            longitude1 = Math.toRadians( longitude1 );
+            latitude2 = Math.toRadians( latitude2 );
+            longitude2 = Math.toRadians( longitude2 );
+            double cLa1 = Math.cos( latitude1 );
+            double xA = EARTH_RADIUS * cLa1 * Math.cos( longitude1 );
+            double yA = EARTH_RADIUS * cLa1 * Math.sin( longitude1 );
+            double zA = EARTH_RADIUS * Math.sin( latitude1 );
+            double cLa2 = Math.cos( latitude2 );
+            double xB = EARTH_RADIUS * cLa2 * Math.cos( longitude2 );
+            double yB = EARTH_RADIUS * cLa2 * Math.sin( longitude2 );
+            double zB = EARTH_RADIUS * Math.sin( latitude2 );
+            return Math.sqrt( ( xA - xB ) * ( xA - xB ) + ( yA - yB )
+                    * ( yA - yB ) + ( zA - zB ) * ( zA - zB ) );
+        }
+        // -- end from org.neo4j.graphalgo.impl.util.GeoEstimateEvaluator
+
+        private double[] getCoordinates(Node node) {
+            return ((PointValue) node.getProperty(pointPropertyKey)).coordinate();
+        }
+    }
+
     @Context
     public GraphDatabaseService db;
 
@@ -45,8 +94,8 @@ public Stream<WeightedPathResult> aStar(
     }
 
     @Procedure
-    @Description("apoc.algo.aStar(startNode, endNode, 'KNOWS|<WORKS_WITH|IS_MANAGER_OF>', {weight:'dist',default:10," +
-            "x:'lon',y:'lat'}) YIELD path, weight - run A* with relationship property name as cost function")
+    @Description("apoc.algo.aStarConfig(startNode, endNode, 'KNOWS|<WORKS_WITH|IS_MANAGER_OF>', {weight:'dist',default:10," +
+            "x:'lon',y:'lat', pointPropName:'point'}) YIELD path, weight - run A* with relationship property name as cost function")
     public Stream<WeightedPathResult> aStarConfig(
             @Name("startNode") Node startNode,
             @Name("endNode") Node endNode,
@@ -56,14 +105,20 @@ public Stream<WeightedPathResult> aStarConfig(
         config = config == null ? Collections.emptyMap() : config;
         String relationshipCostPropertyKey = config.getOrDefault("weight", "distance").toString();
         double defaultCost = ((Number) config.getOrDefault("default", Double.MAX_VALUE)).doubleValue();
-        String latPropertyName = config.getOrDefault("y", "latitude").toString();
-        String lonPropertyName = config.getOrDefault("x", "longitude").toString();
-
+        String pointPropertyName = (String) config.get("pointPropName");
+        final EstimateEvaluator<Double> estimateEvaluator;
+        if (pointPropertyName != null) {
+            estimateEvaluator = new GeoEstimateEvaluatorPointCustom(pointPropertyName);
+        } else {
+            String latPropertyName = config.getOrDefault("y", "latitude").toString();
+            String lonPropertyName = config.getOrDefault("x", "longitude").toString();
+            estimateEvaluator = CommonEvaluators.geoEstimateEvaluator(latPropertyName, lonPropertyName);
+        }
         PathFinder<WeightedPath> algo = GraphAlgoFactory.aStar(
                 new BasicEvaluationContext(tx, db),
                 buildPathExpander(relTypesAndDirs),
                 CommonEvaluators.doubleCostEvaluator(relationshipCostPropertyKey, defaultCost),
-                CommonEvaluators.geoEstimateEvaluator(latPropertyName, lonPropertyName));
+                estimateEvaluator);
         return WeightedPathResult.streamWeightedPathResult(startNode, endNode, algo);
     }
 
@@ -125,7 +180,7 @@ public Stream<WeightedPathResult> dijkstraWithDefaultWeight(
         return WeightedPathResult.streamWeightedPathResult(startNode, endNode, algo);
     }
 
-    private PathExpander<Double> buildPathExpander(String relationshipsAndDirections) {
+    public static PathExpander<Double> buildPathExpander(String relationshipsAndDirections) {
         PathExpanderBuilder builder = PathExpanderBuilder.empty();
         for (Pair<RelationshipType, Direction> pair : RelationshipTypeAndDirections
                 .parse(relationshipsAndDirections)) {

core/src/test/java/apoc/algo/PathFindingTest.java

@@ -15,6 +15,8 @@
 import java.util.List;
 import java.util.Map;
 
+import static apoc.algo.AlgoUtil.SETUP_GEO;
+import static apoc.algo.AlgoUtil.assertAStarResult;
 import static apoc.util.TestUtil.testCall;
 import static apoc.util.TestUtil.testResult;
 import static apoc.util.Util.map;
@@ -46,15 +48,6 @@ public class PathFindingTest {
             "(b)-[:ROAD {d:20}]->(c), " +
             "(c)-[:ROAD {d:30}]->(d), " +
             "(a)-[:ROAD {d:20}]->(c) ";
-    private static final String SETUP_GEO = "CREATE (b:City {name:'Berlin',lat:52.52464,lon:13.40514})\n" +
-            "CREATE (m:City {name:'München',lat:48.1374,lon:11.5755})\n" +
-            "CREATE (f:City {name:'Frankfurt',lat:50.1167,lon:8.68333})\n" +
-            "CREATE (h:City {name:'Hamburg',lat:53.554423,lon:9.994583})\n" +
-            "CREATE (b)-[:DIRECT {dist:255.64*1000}]->(h)\n" +
-            "CREATE (b)-[:DIRECT {dist:504.47*1000}]->(m)\n" +
-            "CREATE (b)-[:DIRECT {dist:424.12*1000}]->(f)\n" +
-            "CREATE (f)-[:DIRECT {dist:304.28*1000}]->(m)\n" +
-            "CREATE (f)-[:DIRECT {dist:393.15*1000}]->(h)";
 
     @Rule
     public DbmsRule db = new ImpermanentDbmsRule();
@@ -87,17 +80,15 @@ public void testAStarConfig() {
         );
     }
 
-    private void assertAStarResult(Result r) {
-        assertEquals(true, r.hasNext());
-        Map<String, Object> row = r.next();
-        assertEquals(697, ((Number)row.get("weight")).intValue()/1000) ;
-        Path path = (Path) row.get("path");
-        assertEquals(2, path.length()) ; // 3nodes, 2 rels
-        List<Node> nodes = Iterables.asList(path.nodes());
-        assertEquals("München", nodes.get(0).getProperty("name")) ;
-        assertEquals("Frankfurt", nodes.get(1).getProperty("name")) ;
-        assertEquals("Hamburg", nodes.get(2).getProperty("name")) ;
-        assertEquals(false,r.hasNext());
+    @Test
+    public void testAStarConfigWithPoint() {
+        db.executeTransactionally(SETUP_GEO);
+        testResult(db,
+                "MATCH (from:City {name:'München'}), (to:City {name:'Hamburg'}) " +
+                        "CALL apoc.algo.aStarConfig(from, to, 'DIRECT', {pointPropName:'coords', weight:'dist', default:100}) yield path, weight " +
+                        "RETURN path, weight" ,
+                AlgoUtil::assertAStarResult
+        );
     }
 
     @Test

docs/asciidoc/modules/ROOT/pages/algorithms/path-finding-procedures.adoc

@@ -11,7 +11,8 @@ APOC exposes some built in path-finding functions that Neo4j brings along.
 | apoc.algo.dijkstra(startNode, endNode, 'KNOWS\|<WORKS_WITH\|IS_MANAGER_OF>', 'distance') YIELD path, weight | run dijkstra with relationship property name as cost function
 | apoc.algo.dijkstraWithDefaultWeight(startNode, endNode, 'KNOWS\|<WORKS_WITH\|IS_MANAGER_OF>',  'distance', 10) YIELD path, weight | run dijkstra with relationship property name as cost function and a default weight if the property does not exist
 | apoc.algo.aStar(startNode, endNode, 'KNOWS\|<WORKS_WITH\|IS_MANAGER_OF>', 'distance','lat','lon')  YIELD path, weight | run A* with relationship property name as cost function
-| apoc.algo.aStar(startNode, endNode, 'KNOWS\|<WORKS_WITH\|IS_MANAGER_OF>', {weight:'dist',default:10, x:'lon',y:'lat'}) YIELD path, weight | run A* with relationship property name as cost function
+| label:apoc-full[] apoc.algo.aStarWithPoint(startNode, endNode, 'relTypesAndDirs', 'weightPropertyName','pointPropertyName') - equivalent to apoc.algo.aStar but accept a Point type as a pointProperty instead of Number types as latitude and longitude properties
+| apoc.algo.aStarConfig(startNode, endNode, 'KNOWS|<WORKS_WITH|IS_MANAGER_OF>', {weight:'dist',default:10, x:'lon',y:'lat',pointPropName:'point'}) YIELD path, weight - run A* with relationship property name as cost function
 | apoc.algo.allSimplePaths(startNode, endNode, 'KNOWS\|<WORKS_WITH\|IS_MANAGER_OF>', 5) YIELD path,  weight | run allSimplePaths with relationships given and maxNodes
 | apoc.stats.degrees(relTypesDirections) yield type, direction, total, min, max, mean, p50, p75, p90, p95, p99, p999 | compute degree distribution in parallel
 |===
@@ -23,4 +24,152 @@ Example: find the weighted shortest path based on relationship property `d` from
 MATCH (from:Loc{name:'A'}), (to:Loc{name:'D'})
 CALL apoc.algo.dijkstra(from, to, 'ROAD', 'd') yield path as path, weight as weight
 RETURN path, weight
+----
+
+==== apoc.algo.aStarConfig
+
+Given this dataset: 
+
+[source,cypher]
+----
+CREATE (b:City {name:'Berlin', coords: point({latitude:52.52464,longitude:13.40514}), lat:52.52464,lon:13.40514})
+CREATE (m:City {name:'München', coords: point({latitude:48.1374,longitude:11.5755}), lat:48.1374,lon:11.5755})
+CREATE (f:City {name:'Frankfurt',coords: point({latitude:50.1167,longitude:8.68333}), lat:50.1167,lon:8.68333})
+CREATE (h:City {name:'Hamburg', coords: point({latitude:53.554423,longitude:9.994583}), lat:53.554423,lon:9.994583})
+CREATE (b)-[:DIRECT {dist:255.64*1000}]->(h)
+CREATE (b)-[:DIRECT {dist:504.47*1000}]->(m)
+CREATE (b)-[:DIRECT {dist:424.12*1000}]->(f)
+CREATE (f)-[:DIRECT {dist:304.28*1000}]->(m)
+CREATE (f)-[:DIRECT {dist:393.15*1000}]->(h)
+----
+
+we can execute (leveraging on 'lat' and 'lon' node properties, which are Numbers,
+on 'dist' relationship property and with default cost 100):
+
+[source,cypher]
+----
+MATCH (from:City {name:'München'}), (to:City {name:'Hamburg'})
+CALL apoc.algo.aStarConfig(from, to, 'DIRECT', {weight:'dist',y:'lat', x:'lon',default:100})
+YIELD weight, path
+RETURN weight, path
+----
+
+.Results
+[opts="header"]
+|===
+| weight | path
+| 697430.0 |
+[source,json]
+----
+{
+  "start": {
+"identity": 1520006,
+"labels": [
+      "City"
+    ],
+"properties": {
+"name": "München",
+"lon": 11.5755,
+"lat": 48.1374,
+"coords": point({srid:4326, x:11.5755, y:48.1374})
+    }
+  },
+  "end": {
+"identity": 1520008,
+"labels": [
+      "City"
+    ],
+"properties": {
+"name": "Hamburg",
+"lon": 9.994583,
+"lat": 53.554423,
+"coords": point({srid:4326, x:9.994583, y:53.554423})
+    }
+  },
+  "segments": [
+    {
+      "start": {
+"identity": 1520006,
+"labels": [
+          "City"
+        ],
+"properties": {
+"name": "München",
+"lon": 11.5755,
+"lat": 48.1374,
+"coords": point({srid:4326, x:11.5755, y:48.1374})
+        }
+      },
+      "relationship": {
+"identity": 3,
+"start": 1520007,
+"end": 1520006,
+"type": "DIRECT",
+"properties": {
+"dist": 304280.0
+        }
+      },
+      "end": {
+"identity": 1520007,
+"labels": [
+          "City"
+        ],
+"properties": {
+"name": "Frankfurt",
+"lon": 8.68333,
+"lat": 50.1167,
+"coords": point({srid:4326, x:8.68333, y:50.1167})
+        }
+      }
+    },
+    {
+      "start": {
+"identity": 1520007,
+"labels": [
+          "City"
+        ],
+"properties": {
+"name": "Frankfurt",
+"lon": 8.68333,
+"lat": 50.1167,
+"coords": point({srid:4326, x:8.68333, y:50.1167})
+        }
+      },
+      "relationship": {
+"identity": 4,
+"start": 1520007,
+"end": 1520008,
+"type": "DIRECT",
+"properties": {
+"dist": 393150.0
+        }
+      },
+      "end": {
+"identity": 1520008,
+"labels": [
+          "City"
+        ],
+"properties": {
+"name": "Hamburg",
+"lon": 9.994583,
+"lat": 53.554423,
+"coords": point({srid:4326, x:9.994583, y:53.554423})
+        }
+      }
+    }
+  ],
+  "length": 2.0
+}
+----
+|===
+
+or equivalently, with the same result, leveraging on 'coords' node property, which is a Point, with the same other configs.
+Note that in case of a 3d-coordinate, the procedure will pick only the x and y or the longitude and latitude values. 
+
+[source,cypher]
+----
+MATCH (from:City {name:'München'}), (to:City {name:'Hamburg'})
+CALL apoc.algo.aStarConfig(from, to, 'DIRECT', {pointPropName:'coords', weight:'dist', default:100})
+YIELD weight, path
+RETURN weight, path
 ----

full/src/main/java/apoc/algo/PathFindingFull.java

@@ -0,0 +1,49 @@
+package apoc.algo;
+
+import apoc.Extended;
+import apoc.result.WeightedPathResult;
+import org.neo4j.graphalgo.BasicEvaluationContext;
+import org.neo4j.graphalgo.CommonEvaluators;
+import org.neo4j.graphalgo.GraphAlgoFactory;
+import org.neo4j.graphalgo.PathFinder;
+import org.neo4j.graphalgo.WeightedPath;
+import org.neo4j.graphdb.GraphDatabaseService;
+import org.neo4j.graphdb.Node;
+import org.neo4j.graphdb.Transaction;
+import org.neo4j.procedure.Context;
+import org.neo4j.procedure.Description;
+import org.neo4j.procedure.Name;
+import org.neo4j.procedure.Procedure;
+
+import java.util.stream.Stream;
+
+import static apoc.algo.PathFinding.buildPathExpander;
+
+@Extended
+public class PathFindingFull {
+
+    @Context
+    public GraphDatabaseService db;
+
+    @Context
+    public Transaction tx;
+
+    @Procedure
+    @Description("apoc.algo.aStarWithPoint(startNode, endNode, 'relTypesAndDirs', 'distance','pointProp') - " +
+            "equivalent to apoc.algo.aStar but accept a Point type as a pointProperty instead of Number types as latitude and longitude properties")
+    public Stream<WeightedPathResult> aStarWithPoint(
+            @Name("startNode") Node startNode,
+            @Name("endNode") Node endNode,
+            @Name("relationshipTypesAndDirections") String relTypesAndDirs,
+            @Name("weightPropertyName") String weightPropertyName,
+            @Name("pointPropertyName") String pointPropertyName) {
+
+        PathFinder<WeightedPath> algo = GraphAlgoFactory.aStar(
+                new BasicEvaluationContext(tx, db),
+                buildPathExpander(relTypesAndDirs),
+                CommonEvaluators.doubleCostEvaluator(weightPropertyName),
+                new PathFinding.GeoEstimateEvaluatorPointCustom(pointPropertyName));
+        return WeightedPathResult.streamWeightedPathResult(startNode, endNode, algo);
+    }
+
+}

full/src/main/resources/extended.txt

@@ -1,3 +1,4 @@
+apoc.algo.aStarWithPoint
 apoc.bolt.execute
 apoc.bolt.load
 apoc.bolt.load.fromLocal