redpoll.text.TermReducer.java Source code

Introduction

Here is the source code for redpoll.text.TermReducer.java

Source

/** 
 * 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 redpoll.text;

import java.io.IOException;
import java.util.ArrayList;
import java.util.Iterator;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.io.ArrayWritable;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapred.JobConf;
import org.apache.hadoop.mapred.MapReduceBase;
import org.apache.hadoop.mapred.OutputCollector;
import org.apache.hadoop.mapred.Reducer;
import org.apache.hadoop.mapred.Reporter;

/**
 * Collects a words list buffer and caculates the df for terms.
 * @author Jeremy Chow(coderplay@gmail.com)
 */
public class TermReducer extends MapReduceBase implements Reducer<Text, TermWritable, Text, TermWritable> {

    private static final Log log = LogFactory.getLog(TermReducer.class.getName());

    private int dfLimit;

    public void reduce(Text key, Iterator<TermWritable> values, OutputCollector<Text, TermWritable> output,
            Reporter reporter) throws IOException {

        ArrayList<TfWritable> tfs = new ArrayList<TfWritable>();

        while (values.hasNext()) {
            TfWritable value = (TfWritable) values.next().get();
            tfs.add((TfWritable) value);
        }

        int df = tfs.size();
        TfWritable writables[] = new TfWritable[df];
        ArrayWritable aw = new TfArrayWritable(tfs.toArray(writables));

        if (df > dfLimit) {
            // if not stands for documents' total number, then ouput term's tf vector
            if (!key.toString().equals("redpoll.docs.num"))
                output.collect(key, new TermWritable(aw)); // wrap again
            output.collect(key, new TermWritable(new IntWritable(df)));
        }
    }

    @Override
    public void configure(JobConf job) {
        dfLimit = job.getInt("redpoll.text.df.limit", 3);
    }

}