chore: add approx heap size methods to index classes

Author: eduardoramirez

hollow/src/main/java/com/netflix/hollow/core/index/HollowHashIndex.java

@@ -296,6 +296,15 @@ public String[] getMatchFields() {
         return matchFields;
     }
 
+    public long approxHeapFootprintInBytes() {
+        HollowHashIndexState hashState = hashStateVolatile;
+        if (hashState == null) {
+            return 0;
+        }
+        return hashState.getMatchHashTable().approxHeapFootprintInBytes() +
+          hashState.getSelectHashArray().approxHeapFootprintInBytes();
+    }
+
     protected static class HollowHashIndexState {
 
         final FixedLengthElementArray selectHashArray;

hollow/src/main/java/com/netflix/hollow/core/index/HollowPrimaryKeyIndex.java

@@ -656,6 +656,14 @@ public Object[] getRecordKey(int ordinal) {
         return keyDeriver.getRecordKey(ordinal);
     }
 
+    public long approxHeapFootprintInBytes() {
+        PrimaryKeyIndexHashTable state = hashTableVolatile;
+        if (state == null) {
+            return 0;
+        }
+        return state.hashTable.approxHeapFootprintInBytes();
+    }
+
     private boolean recordsHaveEqualKeys(int ordinal1, int ordinal2) {
         for(int i=0;i<fieldPathIndexes.length;i++) {
             if(!fieldsAreEqual(ordinal1, ordinal2, i))

hollow/src/main/java/com/netflix/hollow/core/index/HollowUniqueKeyIndex.java

@@ -697,6 +697,14 @@ public Object[] getRecordKey(int ordinal) {
         return results;
     }
 
+    public long approxHeapFootprintInBytes() {
+        PrimaryKeyIndexHashTable state = hashTableVolatile;
+        if (state == null) {
+            return 0;
+        }
+        return state.hashTable.approxHeapFootprintInBytes();
+    }
+
     /**
      * @param ordinal ordinal of root object
      * @param field   field to traverse

hollow/src/test/java/com/netflix/hollow/core/index/HollowHashIndexTest.java

@@ -87,6 +87,15 @@ public void testIndexingStringTypeFieldWithNullValues() throws Exception {
         assertIteratorContainsAll(index.findMatches("onez:").iterator(), 1);
     }
 
+    @Test
+    public void testApproxHeapFootprint() throws Exception {
+        mapper.add(new TypeB(null));
+        mapper.add(new TypeB("onez:"));
+        roundTripSnapshot();
+        HollowHashIndex index = new HollowHashIndex(readStateEngine, "TypeB", "", "b1.value");
+        Assert.assertTrue(index.approxHeapFootprintInBytes() > 0);
+    }
+
     @Test
     public void testIndexingBytesTypeFieldWithNullValues() throws Exception {
         byte[] bytes = {-120,0,0,0};

hollow/src/test/java/com/netflix/hollow/core/index/HollowPrimaryKeyIndexTest.java

@@ -93,6 +93,16 @@ public void testSnapshotAndDelta() throws IOException {
         assertEquals(idx.getRecordKey(3), 3, 3.3d, "three");
     }
 
+    @Test
+    public void testApproxHeapFootprint() throws IOException {
+        HollowObjectMapper mapper = new HollowObjectMapper(writeStateEngine);
+        mapper.add(new TypeA(1, 1.1d, new TypeB("one")));
+        mapper.add(new TypeA(1, 1.1d, new TypeB("1")));
+        mapper.add(new TypeA(2, 2.2d, new TypeB("two")));
+        roundTripSnapshot();
+        HollowPrimaryKeyIndex idx = (HollowPrimaryKeyIndex) createIndex("TypeA");
+        Assert.assertTrue(idx.approxHeapFootprintInBytes() > 0);
+    }
 
     @Test
     public void indicatesWhetherOrNotDuplicateKeysExist() throws IOException {

hollow/src/test/java/com/netflix/hollow/core/index/HollowUniqueKeyIndexTest.java

@@ -88,6 +88,17 @@ public void testSnapshotAndDelta() throws IOException {
         assertEquals(idx.getRecordKey(3), 3, 3.3d, "three");
     }
 
+    @Test
+    public void testApproxHeapFootprint() throws IOException {
+        HollowObjectMapper mapper = new HollowObjectMapper(writeStateEngine);
+
+        mapper.add(new TypeA(1, 1.1d, new TypeB("one")));
+        mapper.add(new TypeA(1, 1.1d, new TypeB("1")));
+        mapper.add(new TypeA(2, 2.2d, new TypeB("two")));
+        roundTripSnapshot();
+        HollowUniqueKeyIndex idx = (HollowUniqueKeyIndex) createIndex("TypeA");
+        Assert.assertTrue(idx.approxHeapFootprintInBytes() > 0);
+    }
 
     @Test
     public void indicatesWhetherOrNotDuplicateKeysExist() throws IOException {