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(",");

更多请见：https://blog.csdn.net/qq_44594249/article/details/96970999