com.google.mr4c.hadoop.MR4CRecordReader.java Source code

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Here is the source code for com.google.mr4c.hadoop.MR4CRecordReader.java

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/**
  * Copyright 2014 Google Inc. All rights reserved.
  * 
  * Licensed 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 com.google.mr4c.hadoop;

import java.io.StringWriter;
import java.util.List;

import org.apache.hadoop.mapred.InputSplit;
import org.apache.hadoop.mapred.RecordReader;
import org.apache.hadoop.io.Text;

public class MR4CRecordReader implements RecordReader<Text, DataKeyList> {

    private MR4CInputSplit m_split;
    private boolean m_done = false;

    // NOTE: treating the entire split as a single hadoop "record"
    // would need additional splitting logic to generate multiple records

    public MR4CRecordReader(MR4CInputSplit split) {
        m_split = split;
    }

    public void close() {
        // no-op
    }

    public Text createKey() {
        return new Text();
    }

    public DataKeyList createValue() {
        return new DataKeyList();
    }

    // NOTE: Position and progress are of limited usefulness as long as we send all the keys as a single record
    // Doing the best we can for now

    public long getPos() {
        return m_done ? 1 : 0; // this could also be number of keys
    }

    public float getProgress() {
        return m_done ? 1.0f : 0.0f;
    }

    public boolean next(Text key, DataKeyList value) {
        if (m_done) {
            return false;
        }
        key.set("" + m_split.getSequenceNumber());
        value.setKeys(m_split.getKeys().getKeys());
        m_done = true;
        return true;
    }

}