hbase-handler/src/java/org/apache/hadoop/hive/hbase/HBaseCompositeKey.java

/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF 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.apache.hadoop.hive.hbase;

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.Map;

import org.apache.hadoop.hive.serde2.lazy.ByteArrayRef;
import org.apache.hadoop.hive.serde2.lazy.LazyFactory;
import org.apache.hadoop.hive.serde2.lazy.LazyObject;
import org.apache.hadoop.hive.serde2.lazy.LazyStruct;
import org.apache.hadoop.hive.serde2.lazy.objectinspector.LazySimpleStructObjectInspector;
import org.apache.hadoop.hive.serde2.objectinspector.ObjectInspector;
import org.apache.hadoop.hive.serde2.objectinspector.StructField;

/**
 * HBaseCompositeKey extension of LazyStruct. All complex composite keys should extend this class
 * and override the {@link LazyStruct#getField(int)} method where fieldID corresponds to the ID of a
 * key in the composite key.
 * <p>
 * For example, for a composite key <i>"/part1/part2/part3"</i>, <i>part1</i> will have an id
 * <i>0</i>, <i>part2</i> will have an id <i>1</i> and <i>part3</i> will have an id <i>2</i>. Custom
 * implementations of getField(fieldID) should return the value corresponding to that fieldID. So,
 * for the above example, the value returned for <i>getField(0)</i> should be </i>part1</i>,
 * <i>getField(1)</i> should be <i>part2</i> and <i>getField(2)</i> should be <i>part3</i>.
 * </p>
 * 
 * <p>
 * All custom implementation are expected to have a constructor of the form:
 * 
 * <pre>
 * MyCustomCompositeKey(LazySimpleStructObjectInspector oi, Properties tbl, Configuration conf)
 * </pre>
 *
 * </p>
 * 
 * */
public class HBaseCompositeKey extends LazyStruct {

  public HBaseCompositeKey(LazySimpleStructObjectInspector oi) {
    super(oi);
  }

  @Override
  public ArrayList<Object> getFieldsAsList() {
    ArrayList<Object> allFields = new ArrayList<Object>();

    List<? extends StructField> fields = oi.getAllStructFieldRefs();

    for (int i = 0; i < fields.size(); i++) {
      allFields.add(getField(i));
    }

    return allFields;
  }

  /**
   * Create an initialize a {@link LazyObject} with the given bytes for the given fieldID.
   * 
   * @param fieldID
   *          field for which the object is to be created
   * @param bytes
   *          value with which the object is to be initialized with
   * @return initialized {@link LazyObject}
   * */
  public LazyObject<? extends ObjectInspector> toLazyObject(int fieldID, byte[] bytes) {
    ObjectInspector fieldOI = oi.getAllStructFieldRefs().get(fieldID).getFieldObjectInspector();

    LazyObject<? extends ObjectInspector> lazyObject = LazyFactory
        .createLazyObject(fieldOI);

    ByteArrayRef ref = new ByteArrayRef();

    ref.setData(bytes);

    // initialize the lazy object
    lazyObject.init(ref, 0, ref.getData().length);

    return lazyObject;
  }

  /**
   * Return the different parts of the key. By default, this returns an empty map. Consumers can
   * choose to override this to provide their own names and types of parts of the key.
   *
   * @return map of parts name to their type
   * */
  public Map<String, String> getParts() {
    return Collections.emptyMap();
  }
}