如何做大表和大表的关联？

如何做大表和大表的关联？ 对于大表和大表的关联： 1.reducejoin可以解决关联问题，但不完美，有数据倾斜的可能，如前所述。 2.思路：将其中一个大表进行切分，成多个小表再进行关联。

package com;

import org.apache.commons.lang.StringUtils;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.NullWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Mapper;
import java.io.BufferedReader;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.HashMap;
import java.util.Map;

public class MapJoinMapper extends Mapper<LongWritable, Text, Text, NullWritable> {
    Map<String, String> dictMap = new HashMap<>();
    Text k = new Text();

    protected void setup(Context context) throws IOException, InterruptedException {
        String path = context.getCacheFiles()[0].getPath();
        BufferedReader br = new BufferedReader(new InputStreamReader(new FileInputStream(path)));
        String line;
        while (StringUtils.isNotEmpty(line = br.readLine())) {
            String[] fields = line.split(",");
            dictMap.put(fields[0], fields[1]+","+fields[2]);
        }
        br.close();
    }

    protected void map(LongWritable key, Text value, Context context) throws IOException, InterruptedException {
        String orderLine = value.toString();
        String[] fields = orderLine.split(",");

更多内容请见原文，文章转载自：https://blog.csdn.net/qq_44594249/article/details/96970999

标签：java,String,fields,关联,做大表,io,new,import,大表
来源： https://www.cnblogs.com/xiaolongxia1922/p/15516149.html