Fix: numShards serialization in rev delta for collection types

Author: Sunjeet

hollow/src/main/java/com/netflix/hollow/core/write/HollowListTypeWriteState.java

@@ -68,7 +68,8 @@ public void prepareForWrite() {
     private void gatherStatistics() {
         if(numShards == -1)
             calculateNumShards();
-        
+        revNumShards = numShards;
+
         int maxOrdinal = ordinalMap.maxOrdinal();
         int maxElementOrdinal = 0;
 

hollow/src/main/java/com/netflix/hollow/core/write/HollowMapTypeWriteState.java

@@ -71,7 +71,8 @@ public void prepareForWrite() {
     private void gatherStatistics() {
         if(numShards == -1)
             calculateNumShards();
-        
+        revNumShards = numShards;
+
         int maxKeyOrdinal = 0;
         int maxValueOrdinal = 0;
 

hollow/src/main/java/com/netflix/hollow/core/write/HollowSetTypeWriteState.java

@@ -69,7 +69,8 @@ public void prepareForWrite() {
     private void gatherStatistics() {
         if(numShards == -1)
             calculateNumShards();
-        
+        revNumShards = numShards;
+
         int maxElementOrdinal = 0;
 
         int maxOrdinal = ordinalMap.maxOrdinal();

hollow/src/test/java/com/netflix/hollow/core/write/HollowTypeWriteStateTest.java

@@ -0,0 +1,93 @@
+package com.netflix.hollow.core.write;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertTrue;
+
+import com.netflix.hollow.api.consumer.HollowConsumer;
+import com.netflix.hollow.api.producer.HollowProducer;
+import com.netflix.hollow.api.producer.fs.HollowInMemoryBlobStager;
+import com.netflix.hollow.test.InMemoryBlobStore;
+import java.util.Arrays;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+import org.junit.Test;
+
+public class HollowTypeWriteStateTest {
+
+    @Test
+    public void testReverseDeltaNumShardsWhenNewTypes() {
+        InMemoryBlobStore blobStore = new InMemoryBlobStore();
+        HollowInMemoryBlobStager blobStager = new HollowInMemoryBlobStager();
+
+        HollowProducer p1 = HollowProducer.withPublisher(blobStore).withBlobStager(blobStager).build();
+        long v1 = p1.runCycle(ws -> ws.add("s1"));
+
+        // add a new object type and all collection types to data model
+        HollowProducer p2 = HollowProducer.withPublisher(blobStore).withBlobStager(blobStager).build();
+        p2.initializeDataModel(HasAllTypes.class);
+        p2.restore(v1, blobStore);
+        long v2 = p2.runCycle(state -> {
+            HasAllTypes o1 = new HasAllTypes(
+                    new CustomReferenceType(5l),
+                    new HashSet<>(Arrays.asList("e1")),
+                    Arrays.asList(1, 2, 3),
+                    new HashMap<String, Long>(){{put("k1", 1L);}}
+            );
+            state.add(o1);
+        });
+
+        HollowConsumer consumer = HollowConsumer.withBlobRetriever(blobStore)
+                .withDoubleSnapshotConfig(new HollowConsumer.DoubleSnapshotConfig() {
+                    @Override
+                    public boolean allowDoubleSnapshot() {
+                        return false;
+                    }
+                    @Override
+                    public int maxDeltasBeforeDoubleSnapshot() {
+                        return Integer.MAX_VALUE;
+                    }
+                })
+                .build();
+        consumer.triggerRefreshTo(v2);
+
+        int numShardsObject = consumer.getStateEngine().getTypeState("CustomReferenceType").numShards();
+        assertTrue(numShardsObject > 0);
+        int numShardsList = consumer.getStateEngine().getTypeState("ListOfInteger").numShards();
+        assertTrue(numShardsList > 0);
+        int numShardsSet = consumer.getStateEngine().getTypeState("SetOfString").numShards();
+        assertTrue(numShardsSet > 0);
+        int numShardsMap = consumer.getStateEngine().getTypeState("MapOfStringToLong").numShards();
+        assertTrue(numShardsMap > 0);
+
+        consumer.triggerRefreshTo(v1);
+        assertEquals(v1, consumer.getCurrentVersionId());
+        assertEquals(numShardsObject, consumer.getStateEngine().getTypeState("CustomReferenceType").numShards());
+        assertEquals(numShardsList, consumer.getStateEngine().getTypeState("ListOfInteger").numShards());
+        assertEquals(numShardsSet, consumer.getStateEngine().getTypeState("SetOfString").numShards());
+        assertEquals(numShardsMap, consumer.getStateEngine().getTypeState("MapOfStringToLong").numShards());
+    }
+
+    private class HasAllTypes {
+        CustomReferenceType customReferenceType;
+        Set<String> setOfStrings;
+        List<Integer> listOfInt;
+        Map<String, Long> mapOfStringToLong;
+
+        private HasAllTypes(CustomReferenceType customReferenceType, Set<String> setOfStrings, List<Integer> listOfInt, Map<String, Long> mapOfStringToLong) {
+            this.customReferenceType = customReferenceType;
+            this.setOfStrings = setOfStrings;
+            this.listOfInt = listOfInt;
+            this.mapOfStringToLong = mapOfStringToLong;
+        }
+    }
+
+    private class CustomReferenceType {
+        long id;
+        private CustomReferenceType(long id) {
+            this.id = id;
+        }
+    }
+}