Implement Merge on Read Storage (#76)

1. Create HoodieTable abstraction for commits and fileSystemView
2. HoodieMergeOnReadTable created
3. View is now always obtained from the table and the correct view based on the table type is returned

hoodie-client/src/main/java/com/uber/hoodie/table/HoodieMergeOnReadTable.java

@@ -0,0 +1,62 @@
+/*
+ * Copyright (c) 2016 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.table;
+
+import com.uber.hoodie.WriteStatus;
+import com.uber.hoodie.common.model.HoodieRecord;
+import com.uber.hoodie.common.model.HoodieRecordPayload;
+import com.uber.hoodie.common.table.HoodieTableMetaClient;
+import com.uber.hoodie.config.HoodieWriteConfig;
+import com.uber.hoodie.io.HoodieAppendHandle;
+import org.apache.log4j.LogManager;
+import org.apache.log4j.Logger;
+
+import java.io.IOException;
+import java.util.Collections;
+import java.util.Iterator;
+import java.util.List;
+
+/**
+ * Implementation of a more real-time read-optimized Hoodie Table where
+ *
+ * INSERTS - Same as HoodieCopyOnWriteTable - Produce new files, block aligned to desired size (or)
+ *           Merge with the smallest existing file, to expand it
+ *
+ * UPDATES - Appends the changes to a rolling log file maintained per file Id.
+ * Compaction merges the log file into the base file.
+ *
+ */
+public class HoodieMergeOnReadTable<T extends HoodieRecordPayload> extends HoodieCopyOnWriteTable<T> {
+    private static Logger logger = LogManager.getLogger(HoodieMergeOnReadTable.class);
+
+    public HoodieMergeOnReadTable(HoodieWriteConfig config,
+        HoodieTableMetaClient metaClient) {
+        super(config, metaClient);
+    }
+
+    @Override
+    public Iterator<List<WriteStatus>> handleUpdate(String commitTime, String fileId,
+        Iterator<HoodieRecord<T>> recordItr) throws IOException {
+        logger.info("Merging updates for commit " + commitTime + " for file " + fileId);
+        HoodieAppendHandle<T> appendHandle =
+            new HoodieAppendHandle<>(config, commitTime, this, fileId, recordItr);
+        appendHandle.doAppend();
+        appendHandle.close();
+        return Collections.singletonList(Collections.singletonList(appendHandle.getWriteStatus()))
+            .iterator();
+    }
+}