trec.TrecRecordReader.java Source code

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Here is the source code for trec.TrecRecordReader.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 trec;

import java.io.IOException;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FSDataInputStream;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.io.compress.CompressionCodec;
import org.apache.hadoop.io.compress.CompressionCodecFactory;
import org.apache.hadoop.mapreduce.InputSplit;
import org.apache.hadoop.mapreduce.RecordReader;
import org.apache.hadoop.mapreduce.TaskAttemptContext;
import org.apache.hadoop.mapreduce.lib.input.FileSplit;
import org.apache.hadoop.util.LineReader;

/**
 * Treats keys as offset in file and value as line.
 */
public class TrecRecordReader extends RecordReader<LongWritable, Text> {

    private CompressionCodecFactory compressionCodecs = null;
    private long start;
    private long pos;
    private long end;
    private LineReader in;
    private LongWritable key = null;
    private Text value = null;

    public void initialize(InputSplit genericSplit, TaskAttemptContext context) throws IOException {
        FileSplit split = (FileSplit) genericSplit;
        Configuration job = context.getConfiguration();
        start = split.getStart();
        end = start + split.getLength();
        final Path file = split.getPath();
        compressionCodecs = new CompressionCodecFactory(job);
        final CompressionCodec codec = compressionCodecs.getCodec(file);

        // open the file and seek to the start of the split
        FileSystem fs = file.getFileSystem(job);
        FSDataInputStream fileIn = fs.open(split.getPath());
        boolean skipFirstLine = false;
        if (codec != null) {
            in = new LineReader(codec.createInputStream(fileIn), job);
            end = Long.MAX_VALUE;
        } else {
            if (start != 0) {
                skipFirstLine = true;
                --start;
                fileIn.seek(start);
            }
            in = new LineReader(fileIn, job);
        }
        if (skipFirstLine) { // skip first line and re-establish "start".
            start += in.readLine(new Text(), 0, (int) Math.min((long) Integer.MAX_VALUE, end - start));
        }
        this.pos = start;
    }

    public int nextLine() throws IOException {
        int size = in.readLine(line, Integer.MAX_VALUE, Integer.MAX_VALUE);
        pos += size;
        return size;
    }

    Text headline = null;
    Text line = new Text();

    public boolean nextKeyValue() throws IOException {
        if (pos >= end) {
            return false;
        }
        if (key == null) {
            key = new LongWritable();
        }
        key.set(pos);
        if (value == null) {
            value = new Text();
        }
        String recordStr = new String();
        if (headline == null) {
            while (!recordStr.startsWith("###")) {
                if (pos >= end) {
                    return false;
                }
                int size = nextLine();
                if (size == 0) {
                    key = null;
                    value = null;
                    return false;
                }
                recordStr = line.toString();
            }
        } else {
            recordStr = headline.toString();
            headline = null;
        }
        while (true) {
            int size = nextLine();
            if (line.toString().startsWith("###"))
                headline = new Text(line);
            if (size == 0 || line.toString().startsWith("###")) {
                break;
            }
            recordStr += "\n" + line;
        }
        value.set(recordStr);
        return true;
    }

    @Override
    public LongWritable getCurrentKey() {
        return key;
    }

    @Override
    public Text getCurrentValue() {
        return value;
    }

    /**
     * Get the progress within the split
     */
    public float getProgress() {
        if (start == end) {
            return 0.0f;
        } else {
            return Math.min(1.0f, (pos - start) / (float) (end - start));
        }
    }

    public synchronized void close() throws IOException {
        if (in != null) {
            in.close();
        }
    }
}