1 /**
2 * Copyright 2009 The Apache Software Foundation
3 *
4 * Licensed to the Apache Software Foundation (ASF) under one
5 * or more contributor license agreements. See the NOTICE file
6 * distributed with this work for additional information
7 * regarding copyright ownership. The ASF licenses this file
8 * to you under the Apache License, Version 2.0 (the
9 * "License"); you may not use this file except in compliance
10 * with the License. You may obtain a copy of the License at
11 *
12 * http://www.apache.org/licenses/LICENSE-2.0
13 *
14 * Unless required by applicable law or agreed to in writing, software
15 * distributed under the License is distributed on an "AS IS" BASIS,
16 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
17 * See the License for the specific language governing permissions and
18 * limitations under the License.
19 */
20 package org.apache.hadoop.hbase.mapreduce;
21
22 import java.util.TreeSet;
23
24 import org.apache.hadoop.hbase.KeyValue;
25 import org.apache.hadoop.hbase.io.ImmutableBytesWritable;
26 import org.apache.hadoop.mapreduce.Reducer;
27
28 /**
29 * Emits sorted KeyValues.
30 * Reads in all KeyValues from passed Iterator, sorts them, then emits
31 * KeyValues in sorted order. If lots of columns per row, it will use lots of
32 * memory sorting.
33 * @see HFileOutputFormat
34 */
35 public class KeyValueSortReducer extends Reducer<ImmutableBytesWritable, KeyValue, ImmutableBytesWritable, KeyValue> {
36 protected void reduce(ImmutableBytesWritable row, java.lang.Iterable<KeyValue> kvs,
37 org.apache.hadoop.mapreduce.Reducer<ImmutableBytesWritable, KeyValue, ImmutableBytesWritable, KeyValue>.Context context)
38 throws java.io.IOException, InterruptedException {
39 TreeSet<KeyValue> map = new TreeSet<KeyValue>(KeyValue.COMPARATOR);
40 for (KeyValue kv: kvs) {
41 map.add(kv.clone());
42 }
43 context.setStatus("Read " + map.getClass());
44 int index = 0;
45 for (KeyValue kv: map) {
46 context.write(row, kv);
47 if (index > 0 && index % 100 == 0) context.setStatus("Wrote " + index);
48 }
49 }
50 }