Fix community count computation for long based ids

Co-Authored-By: Paul Horn <[email protected]>

Author: jjaderberg

algo-common/src/main/java/org/neo4j/graphalgo/result/AbstractCommunityResultBuilder.java

@@ -100,7 +100,7 @@ private void buildCommunityCount() {
         long communityCount = 0L;
 
         SparseNodeMapping componentSizes = buildComponentSizes();
-        for (int communityId = 0; communityId < componentSizes.getCapacity(); communityId++) {
+        for (long communityId = 0; communityId < componentSizes.getCapacity(); communityId++) {
             long communitySize = componentSizes.get(communityId);
             if (communitySize > 0) {
                 communityCount++;

proc/common/src/test/java/org/neo4j/graphalgo/result/AbstractCommunityResultBuilderTest.java

@@ -176,6 +176,24 @@ void oneCommunityFromHugeMap() {
         assertEquals(4.0, histogram.getValueAtPercentile(100D), 0.01);
     }
 
+    @Test
+    void buildCommunityCountWithHugeCommunityCount() {
+        AbstractCommunityResultBuilder<Void> builder = builder(
+            procedureCallContext("communityCount"),
+            (maybeCommunityCount, maybeHistogram) -> {
+                assertTrue(maybeCommunityCount.isPresent());
+                assertFalse(maybeHistogram.isPresent());
+                long communityCount = maybeCommunityCount.orElse(-1);
+                assertEquals(2L, communityCount, "should build 2 communities");
+            });
+
+        LongUnaryOperator communityFunction = n -> n % 2 == 0 ? 0 : ((long) Integer.MAX_VALUE) + 2;
+        builder
+            .withCommunityFunction(communityFunction)
+            .withNodeCount(2)
+            .build();
+    }
+
     @Test
     void buildCommunityHistogramWithHugeCommunityCount() {
         AbstractCommunityResultBuilder<Void> builder = builder(