Implement support for bulk delete operation

mr/src/main/java/org/elasticsearch/hadoop/cfg/Settings.java

@@ -166,6 +166,11 @@ public String getSerializerValueWriterClassName() {
         return getProperty(ES_SERIALIZATION_WRITER_VALUE_CLASS);
     }
 
+    public Settings setSerializerValueWriterClassName(String className) {
+        setProperty(ES_SERIALIZATION_WRITER_VALUE_CLASS, className);
+        return this;
+    }
+
     public String getSerializerBytesConverterClassName() {
         return getProperty(ES_SERIALIZATION_WRITER_BYTES_CLASS);
     }

mr/src/main/java/org/elasticsearch/hadoop/serialization/bulk/BulkCommands.java

@@ -45,8 +45,11 @@ else if (ConfigurationOptions.ES_OPERATION_UPDATE.equals(operation)) {
         else if (ConfigurationOptions.ES_OPERATION_UPSERT.equals(operation)) {
             factory = new UpdateBulkFactory(settings, true, metaExtractor, version);
         }
+        else if (ConfigurationOptions.ES_OPERATION_DELETE.equals(operation)) {
+            factory = new DeleteBulkFactory(settings, metaExtractor, version);
+        }
         else {
-            throw new EsHadoopIllegalArgumentException("Unknown operation " + operation);
+            throw new EsHadoopIllegalArgumentException("Unsupported bulk operation " + operation);
         }
 
         return factory.createBulk();

mr/src/main/java/org/elasticsearch/hadoop/serialization/bulk/DeleteBulkFactory.java

@@ -0,0 +1,55 @@
+/*
+ * Licensed to Elasticsearch under one or more contributor
+ * license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright
+ * ownership. Elasticsearch 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 org.elasticsearch.hadoop.serialization.bulk;
+
+import org.elasticsearch.hadoop.cfg.ConfigurationOptions;
+import org.elasticsearch.hadoop.cfg.Settings;
+import org.elasticsearch.hadoop.serialization.Generator;
+import org.elasticsearch.hadoop.serialization.builder.ValueWriter;
+import org.elasticsearch.hadoop.util.EsMajorVersion;
+
+import java.util.List;
+
+class DeleteBulkFactory extends AbstractBulkFactory {
+
+    public static final class NoDataWriter<T> implements ValueWriter<T> {
+
+        @Override
+        public Result write(Object object, Generator generator) {
+            // do nothing, delete doesn't require any content
+            return Result.SUCCESFUL();
+        }
+    }
+
+    public DeleteBulkFactory(Settings settings, MetadataExtractor metaExtractor, EsMajorVersion version) {
+        // we only want a specific serializer for this particular bulk factory
+        super(settings.copy().setSerializerValueWriterClassName(NoDataWriter.class.getName()), metaExtractor, version);
+    }
+
+    @Override
+    protected String getOperation() {
+        return ConfigurationOptions.ES_OPERATION_DELETE;
+    }
+
+    @Override
+    protected void writeObjectEnd(List<Object> list) {
+        // skip adding new-line for each entity as delete doesn't need entity output
+        list.add("");
+    }
+}