Merge pull request #5538 from IoannisPanagiotas/port-consecutiveIds-louvain

Fix Louvain bug when consecutiveIds is enabled

Author: IoannisPanagiotas

proc/community/src/main/java/org/neo4j/gds/louvain/LouvainStreamProc.java

@@ -79,17 +79,29 @@ protected Stream<StreamResult> stream(ComputationResult<Louvain, Louvain, Louvai
         return runWithExceptionLogging("Graph streaming failed", () -> {
             Graph graph = computationResult.graph();
 
+            boolean consecutiveIds = computationResult
+                .config()
+                .consecutiveIds();
+
+            var nodeProperties = (computationResult.isGraphEmpty() || !consecutiveIds) ? null : nodeProperties((computationResult));
+
             return LongStream
                 .range(0, graph.nodeCount())
                 .boxed()
                 .map((nodeId) -> {
                     boolean includeIntermediateCommunities = computationResult
                         .config()
                         .includeIntermediateCommunities();
+
                     Louvain louvain = computationResult.result();
                     long[] communities = includeIntermediateCommunities ? louvain.getCommunities(nodeId) : null;
-
-                    return new StreamResult(graph.toOriginalNodeId(nodeId), communities, louvain.getCommunity(nodeId));
+                    long communityId = consecutiveIds ? nodeProperties.longValue(
+                        nodeId) : louvain.getCommunity(nodeId);
+                    return new StreamResult(
+                        graph.toOriginalNodeId(nodeId),
+                        communities,
+                        communityId
+                    );
                 });
         });
     }

proc/community/src/test/java/org/neo4j/gds/louvain/LouvainStreamProcTest.java

@@ -26,6 +26,7 @@
 import org.neo4j.gds.core.CypherMapWrapper;
 
 import java.util.ArrayList;
+import java.util.HashSet;
 import java.util.List;
 
 import static org.assertj.core.api.Assertions.assertThat;
@@ -58,6 +59,30 @@ void testStream() {
         assertCommunities(actualCommunities, RESULT);
     }
 
+    @Test
+    void testStreamConsecutiveIds() {
+        @Language("Cypher") String query = GdsCypher.call("myGraph")
+            .algo("louvain")
+            .streamMode()
+            .addParameter("consecutiveIds", true)
+            .yields("nodeId", "communityId", "intermediateCommunityIds");
+
+        var communityMap = new HashSet<Long>();
+
+        List<Long> actualCommunities = new ArrayList<>();
+        runQueryWithRowConsumer(query, row -> {
+            int id = row.getNumber("nodeId").intValue();
+            long community = row.getNumber("communityId").longValue();
+            communityMap.add(community);
+            assertNull(row.get("intermediateCommunityIds"));
+            actualCommunities.add(id, community);
+        });
+        assertCommunities(actualCommunities, RESULT);
+        assertThat(communityMap).hasSize(3).containsExactlyInAnyOrder(0L, 1L, 2L);
+
+    }
+
+
     @Test
     void testStreamCommunities() {
         @Language("Cypher") String query = GdsCypher.call("myGraph")