Add empty payload class to support deletes via apache spark

hoodie-spark/src/main/java/com/uber/hoodie/EmptyHoodieRecordPayload.java

@@ -0,0 +1,48 @@
+/*
+ *  Copyright (c) 2019 Uber Technologies, Inc. (hoodie-dev-group@uber.com)
+ *
+ *  Licensed 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 com.uber.hoodie;
+
+import com.uber.hoodie.common.model.HoodieRecordPayload;
+import java.util.Optional;
+import org.apache.avro.Schema;
+import org.apache.avro.generic.GenericRecord;
+import org.apache.avro.generic.IndexedRecord;
+
+/**
+ * Empty payload used for deletions
+ */
+public class EmptyHoodieRecordPayload implements HoodieRecordPayload<EmptyHoodieRecordPayload> {
+
+  public EmptyHoodieRecordPayload(GenericRecord record, Comparable orderingVal) { }
+
+  @Override
+  public EmptyHoodieRecordPayload preCombine(EmptyHoodieRecordPayload another) {
+    return another;
+  }
+
+  @Override
+  public Optional<IndexedRecord> combineAndGetUpdateValue(IndexedRecord currentValue, Schema schema) {
+    return Optional.empty();
+  }
+
+  @Override
+  public Optional<IndexedRecord> getInsertValue(Schema schema) {
+    return Optional.empty();
+  }
+}