older segments might not have field bitmapSerdeFactory for dimension columns and we must use appropriate default

processing/src/main/java/io/druid/segment/serde/DictionaryEncodedColumnPartSerde.java

@@ -31,6 +31,7 @@ import io.druid.segment.CompressedVSizeIndexedV3Supplier;
 import io.druid.segment.column.ColumnBuilder;
 import io.druid.segment.column.ColumnConfig;
 import io.druid.segment.column.ValueType;
+import io.druid.segment.data.BitmapSerde;
 import io.druid.segment.data.BitmapSerdeFactory;
 import io.druid.segment.data.ByteBufferSerializer;
 import io.druid.segment.data.ByteBufferWriter;
@@ -93,7 +94,11 @@ public class DictionaryEncodedColumnPartSerde implements ColumnPartSerde
       @NotNull @JsonProperty("byteOrder") ByteOrder byteOrder
   )
   {
-    return new DictionaryEncodedColumnPartSerde(byteOrder, bitmapSerdeFactory, null);
+    return new DictionaryEncodedColumnPartSerde(
+        byteOrder,
+        bitmapSerdeFactory != null ? bitmapSerdeFactory : new BitmapSerde.LegacyBitmapSerdeFactory(),
+        null
+    );
   }
 
   private final ByteOrder byteOrder;

processing/src/test/java/io/druid/segment/serde/DictionaryEncodedColumnPartSerdeTest.java

@@ -0,0 +1,73 @@
+/*
+ * Licensed to Metamarkets Group Inc. (Metamarkets) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. Metamarkets licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied. See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+package io.druid.segment.serde;
+
+import com.fasterxml.jackson.databind.ObjectMapper;
+import io.druid.segment.TestHelper;
+import io.druid.segment.data.ConciseBitmapSerdeFactory;
+import io.druid.segment.data.RoaringBitmapSerdeFactory;
+import org.junit.Assert;
+import org.junit.Test;
+
+import java.nio.ByteOrder;
+
+/**
+ */
+public class DictionaryEncodedColumnPartSerdeTest
+{
+  @Test
+  public void testSerde() throws Exception
+  {
+    //bitmapSerdeFactory not specified
+    String json = "{\n"
+                  + " \"type\": \"stringDictionary\",\n"
+                  + " \"byteOrder\": \"BIG_ENDIAN\"\n"
+                  + "}\n";
+
+    ObjectMapper mapper = TestHelper.getObjectMapper();
+
+    DictionaryEncodedColumnPartSerde serde = (DictionaryEncodedColumnPartSerde) mapper.readValue(
+        mapper.writeValueAsString(
+            mapper.readValue(json, ColumnPartSerde.class)
+        ),
+        ColumnPartSerde.class
+    );
+
+    Assert.assertEquals(ByteOrder.BIG_ENDIAN, serde.getByteOrder());
+    Assert.assertTrue(serde.getBitmapSerdeFactory() instanceof ConciseBitmapSerdeFactory);
+
+    //bitmapSerdeFactory specified
+    json = "{\n"
+           + "\"type\": \"stringDictionary\",\n"
+           + "\"byteOrder\": \"LITTLE_ENDIAN\",\n"
+           + "\"bitmapSerdeFactory\": { \"type\": \"roaring\" }\n"
+           + "}";
+
+    serde = (DictionaryEncodedColumnPartSerde) mapper.readValue(
+        mapper.writeValueAsString(
+            mapper.readValue(json, ColumnPartSerde.class)
+        ),
+        ColumnPartSerde.class
+    );
+
+    Assert.assertEquals(ByteOrder.LITTLE_ENDIAN, serde.getByteOrder());
+    Assert.assertTrue(serde.getBitmapSerdeFactory() instanceof RoaringBitmapSerdeFactory);
+  }
+}