Ensure Hoodie works for non-partitioned Hive table

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

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+/*
+ *  Copyright (c) 2017 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.HoodieKey;
+import com.uber.hoodie.common.util.TypedProperties;
+import org.apache.avro.generic.GenericRecord;
+
+/**
+ * Simple Key generator for unpartitioned Hive Tables
+ */
+public class NonpartitionedKeyGenerator extends SimpleKeyGenerator {
+
+  private static final String EMPTY_PARTITION = "";
+
+  public NonpartitionedKeyGenerator(TypedProperties props) {
+    super(props);
+  }
+
+  @Override
+  public HoodieKey getKey(GenericRecord record) {
+    String recordKey = DataSourceUtils.getNestedFieldValAsString(record, recordKeyField);
+    return new HoodieKey(recordKey, EMPTY_PARTITION);
+  }
+}