Hadoop MapReduce 学习笔记(十一) MapReduce实现类似SQL的order by/排序3 改进

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       请先阅读:           

           1.Hadoop MapReduce 学习笔记(一) 序言和准备

           2.Hadoop MapReduce 学习笔记(二) 序言和准备 2

               3.Hadoop MapReduce 学习笔记(八) MapReduce实现类似SQL的order by/排序

                4.Hadoop MapReduce 学习笔记(九) MapReduce实现类似SQL的order by/排序 正确写法

                5.Hadoop MapReduce 学习笔记(十) MapReduce实现类似SQL的order by/排序2 对多个字段排序

 

          下一篇:Hadoop MapReduce 学习笔记(十二) MapReduce实现类似SQL的order by/排序3 改进及改正

 

       Hadoop MapReduce 学习笔记(十) MapReduce实现类似SQL的order by/排序2 对多个字段排序 可以实现对多个字段的order by/排序.但这里想引入2个参数,因为这2个参数对性能有所提升,所以再补充了这篇博客.具体还是看代码吧.

 

package com.guoyun.hadoop.mapreduce.study;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.NullWritable;
import org.apache.hadoop.io.RawComparator;
import org.apache.hadoop.io.WritableComparator;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.Partitioner;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;


/**
 * 通过MapReduce实现类似SELECT ＊ FROM TABLE ORDER BY COL1 ASC，COL2 DESC功能
 * 也就是对多个字段的排序
 * 相比 ＠OrderByMultiMapReduceTest,主要引入了Partitioner和GroupingComparator,提升性能
 * 由于生成的数据frameworkName比较固定(具体请查看 @MyMapReduceMultiColumnTest 如何生成的数据)
 * 所以这里获取map输出key的frameworkName属性,交给Partitioner和GroupingComparator来确定相同
 * frameworkName的数据输出到相同的Reduce上,尽可能减少Reduce之前的清洗和排序工作,提升性能.
 * 具体Partitioner和GroupingComparator的用法请查看Hadoop说明
 * 这里只是我目前对Partitioner和GroupingComparator的理解,刻意安排的输入数据.一切还需要验证中,待有机会
 * 查看map和reduce源码后再来求证.
 * 但运行本类后结果和MROutput_Multi_OrderBy并不一致,正确的实现方法请查看类 @OrderByMultiMapReduceImproveFixTest
 */
public class OrderByMultiMapReduceImproveTest extends
  OrderByMultiMapReduceTest {
  public static final Logger log=LoggerFactory.getLogger(OrderByMultiMapReduceImproveTest.class);
  
  public OrderByMultiMapReduceImproveTest(long dataLength) throws Exception {
    super(dataLength);
    // TODO Auto-generated constructor stub
  }

  public OrderByMultiMapReduceImproveTest(String outputPath) throws Exception {
    super(outputPath);
    // TODO Auto-generated constructor stub
  }

  public OrderByMultiMapReduceImproveTest(String inputPath, String outputPath) {
    super(inputPath, outputPath);
  }

  public OrderByMultiMapReduceImproveTest(long dataLength, String inputPath,
      String outputPath) throws Exception {
    super(dataLength, inputPath, outputPath);
    // TODO Auto-generated constructor stub
  }
  
  /**
   * partitioner
   */
  public static class MyPartitioner extends Partitioner<OrderMultiColumnWritable,NullWritable>{

    @Override
    public int getPartition(OrderMultiColumnWritable key, NullWritable value,
        int numbers) {
      return (int)Math.abs(key.getFrameworkName().hashCode()%numbers);
    }
    
  }

  public static class MyComparator extends WritableComparator {
    public MyComparator() {
      super(OrderMultiColumnWritable.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(OrderMultiColumnWritable.class, new MyComparator());
  }
  
  /**
   * GroupingComparator
   */
  public static class MyGroupingComparator implements RawComparator<OrderMultiColumnWritable>{

    @Override
    public int compare(OrderMultiColumnWritable o1,
        OrderMultiColumnWritable o2) {
      return o1.getFrameworkName().compareTo(o2.getFrameworkName());
      //return o1.compareTo(o2);
    }

    @Override
    public int compare(byte[] b1, int s1, int l1, byte[] b2, int s2,
        int l2) {
      return WritableComparator.compareBytes(b1,s1,l1,b2,s2,l2);
    }
    
  }
  
  public static void main(String[] args){
    MyMapReduceTest mapReduceTest=null;
    Configuration conf=null;
    Job job=null;
    FileSystem fs=null;
    Path inputPath=null;
    Path outputPath=null;
    long begin=0;
    String input="testDatas/mapreduce/MRInput_Multi_OrderBy";
    String output="testDatas/mapreduce/MROutput_Multi_OrderBy_Improve";
    
    
    try {
      // 直接使用MRInput_Single_OrderBy的输入数据,不重新生成数据,以便比对结果是否正确
      // 和MROutput_Multi_OrderBy进行比对
      mapReduceTest=new OrderByMultiMapReduceImproveTest(input,output);
      
      inputPath=new Path(mapReduceTest.getInputPath());
      outputPath=new Path(mapReduceTest.getOutputPath());
      
      conf=new Configuration();
      job=new Job(conf,"OrderBy");
      
      fs=FileSystem.getLocal(conf);
      if(fs.exists(outputPath)){
        if(!fs.delete(outputPath,true)){
          System.err.println("Delete output file:"+mapReduceTest.getOutputPath()+" failed!");
          return;
        }
      }
      
      
      job.setJarByClass(OrderByMultiMapReduceImproveTest.class);
      job.setMapOutputKeyClass(OrderMultiColumnWritable.class);
      job.setMapOutputValueClass(NullWritable.class);
      job.setOutputKeyClass(OrderMultiColumnWritable.class);
      job.setOutputValueClass(NullWritable.class);
      job.setMapperClass(MyMapper.class);
      job.setReducerClass(MyReducer.class);
      
      job.setPartitionerClass(MyPartitioner.class);
      job.setGroupingComparatorClass(MyGroupingComparator.class);
      
      job.setNumReduceTasks(2);
      
      FileInputFormat.addInputPath(job, inputPath);
      FileOutputFormat.setOutputPath(job, outputPath);
      
      begin=System.currentTimeMillis();
      job.waitForCompletion(true);
      
      System.out.println("===================================================");
      if(mapReduceTest.isGenerateDatas()){
        System.out.println("The maxValue is:"+mapReduceTest.getMaxValue());
        System.out.println("The minValue is:"+mapReduceTest.getMinValue());
      }
      System.out.println("Spend time:"+(System.currentTimeMillis()-begin));
      // Spend time:1280
      
    } catch (Exception e) {
      // TODO Auto-generated catch block
      e.printStackTrace();
    }
    
  }
  
}

 

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