HADOOP-4545. Missed a file.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/core/branches/branch-0.20@727088 13f79535-47bb-0310-9956-ffa450edef68

src/examples/org/apache/hadoop/examples/SecondarySort.java

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+/**
+ * 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.examples;
+
+import java.io.DataInput;
+import java.io.DataOutput;
+import java.io.IOException;
+import java.util.StringTokenizer;
+
+import org.apache.hadoop.conf.Configuration;
+import org.apache.hadoop.fs.Path;
+import org.apache.hadoop.io.IntWritable;
+import org.apache.hadoop.io.LongWritable;
+import org.apache.hadoop.io.RawComparator;
+import org.apache.hadoop.io.Text;
+import org.apache.hadoop.io.WritableComparable;
+import org.apache.hadoop.io.WritableComparator;
+import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
+import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
+import org.apache.hadoop.mapreduce.Job;
+import org.apache.hadoop.mapreduce.Mapper;
+import org.apache.hadoop.mapreduce.Partitioner;
+import org.apache.hadoop.mapreduce.Reducer;
+import org.apache.hadoop.util.GenericOptionsParser;
+
+/**
+ * This is an example Hadoop Map/Reduce application.
+ * It reads the text input files that must contain two integers per a line.
+ * The output is sorted by the first and second number and grouped on the 
+ * first number.
+ *
+ * To run: bin/hadoop jar build/hadoop-examples.jar secondarysort
+ *            <i>in-dir</i> <i>out-dir</i> 
+ */
+public class SecondarySort {
+ 
+  /**
+   * Define a pair of integers that are writable.
+   * They are serialized in a byte comparable format.
+   */
+  public static class IntPair 
+                      implements WritableComparable<IntPair> {
+    private int first = 0;
+    private int second = 0;
+    
+    /**
+     * Set the left and right values.
+     */
+    public void set(int left, int right) {
+      first = left;
+      second = right;
+    }
+    public int getFirst() {
+      return first;
+    }
+    public int getSecond() {
+      return second;
+    }
+    /**
+     * Read the two integers. 
+     * Encoded as: MIN_VALUE -> 0, 0 -> -MIN_VALUE, MAX_VALUE-> -1
+     */
+    @Override
+    public void readFields(DataInput in) throws IOException {
+      first = in.readInt() + Integer.MIN_VALUE;
+      second = in.readInt() + Integer.MIN_VALUE;
+    }
+    @Override
+    public void write(DataOutput out) throws IOException {
+      out.writeInt(first - Integer.MIN_VALUE);
+      out.writeInt(second - Integer.MIN_VALUE);
+    }
+    @Override
+    public int hashCode() {
+      return first * 157 + second;
+    }
+    @Override
+    public boolean equals(Object right) {
+      if (right instanceof IntPair) {
+        IntPair r = (IntPair) right;
+        return r.first == first && r.second == second;
+      } else {
+        return false;
+      }
+    }
+    /** A Comparator that compares serialized IntPair. */ 
+    public static class Comparator extends WritableComparator {
+      public Comparator() {
+        super(IntPair.class);
+      }
+
+      public int compare(byte[] b1, int s1, int l1,
+                         byte[] b2, int s2, int l2) {
+        return compareBytes(b1, s1, l1, b2, s2, l2);
+      }
+    }
+
+    static {                                        // register this comparator
+      WritableComparator.define(IntPair.class, new Comparator());
+    }
+
+    @Override
+    public int compareTo(IntPair o) {
+      if (first != o.first) {
+        return first < o.first ? -1 : 1;
+      } else if (second != o.second) {
+        return second < o.second ? -1 : 1;
+      } else {
+        return 0;
+      }
+    }
+  }
+  
+  /**
+   * Partition based on the first part of the pair.
+   */
+  public static class FirstPartitioner extends Partitioner<IntPair,IntWritable>{
+    @Override
+    public int getPartition(IntPair key, IntWritable value, 
+                            int numPartitions) {
+      return Math.abs(key.getFirst() * 127) % numPartitions;
+    }
+  }
+
+  /**
+   * Compare only the first part of the pair, so that reduce is called once
+   * for each value of the first part.
+   */
+  public static class FirstGroupingComparator 
+                implements RawComparator<IntPair> {
+    @Override
+    public int compare(byte[] b1, int s1, int l1, byte[] b2, int s2, int l2) {
+      return WritableComparator.compareBytes(b1, s1, Integer.SIZE/8, 
+                                             b2, s2, Integer.SIZE/8);
+    }
+
+    @Override
+    public int compare(IntPair o1, IntPair o2) {
+      int l = o1.getFirst();
+      int r = o2.getFirst();
+      return l == r ? 0 : (l < r ? -1 : 1);
+    }
+  }
+
+  /**
+   * Read two integers from each line and generate a key, value pair
+   * as ((left, right), right).
+   */
+  public static class MapClass 
+         extends Mapper<LongWritable, Text, IntPair, IntWritable> {
+    
+    private final IntPair key = new IntPair();
+    private final IntWritable value = new IntWritable();
+    
+    @Override
+    public void map(LongWritable inKey, Text inValue, 
+                    Context context) throws IOException, InterruptedException {
+      StringTokenizer itr = new StringTokenizer(inValue.toString());
+      int left = 0;
+      int right = 0;
+      if (itr.hasMoreTokens()) {
+        left = Integer.parseInt(itr.nextToken());
+        if (itr.hasMoreTokens()) {
+          right = Integer.parseInt(itr.nextToken());
+        }
+        key.set(left, right);
+        value.set(right);
+        context.write(key, value);
+      }
+    }
+  }
+  
+  /**
+   * A reducer class that just emits the sum of the input values.
+   */
+  public static class Reduce 
+         extends Reducer<IntPair, IntWritable, Text, IntWritable> {
+    private static final Text SEPARATOR = 
+      new Text("------------------------------------------------");
+    private final Text first = new Text();
+    
+    @Override
+    public void reduce(IntPair key, Iterable<IntWritable> values,
+                       Context context
+                       ) throws IOException, InterruptedException {
+      context.write(SEPARATOR, null);
+      first.set(Integer.toString(key.getFirst()));
+      for(IntWritable value: values) {
+        context.write(first, value);
+      }
+    }
+  }
+  
+  public static void main(String[] args) throws Exception {
+    Configuration conf = new Configuration();
+    String[] otherArgs = new GenericOptionsParser(conf, args).getRemainingArgs();
+    if (otherArgs.length != 2) {
+      System.err.println("Usage: secondarysrot <in> <out>");
+      System.exit(2);
+    }
+    Job job = new Job(conf, "secondary sort");
+    job.setJarByClass(SecondarySort.class);
+    job.setMapperClass(MapClass.class);
+    job.setReducerClass(Reduce.class);
+
+    // group and partition by the first int in the pair
+    job.setPartitionerClass(FirstPartitioner.class);
+    job.setGroupingComparatorClass(FirstGroupingComparator.class);
+
+    // the map output is IntPair, IntWritable
+    job.setMapOutputKeyClass(IntPair.class);
+    job.setMapOutputValueClass(IntWritable.class);
+
+    // the reduce output is Text, IntWritable
+    job.setOutputKeyClass(Text.class);
+    job.setOutputValueClass(IntWritable.class);
+    
+    FileInputFormat.addInputPath(job, new Path(otherArgs[0]));
+    FileOutputFormat.setOutputPath(job, new Path(otherArgs[1]));
+    System.exit(job.waitForCompletion() ? 0 : 1);
+  }
+
+}