content: /*
   * 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 com.aliyun.odps.mapred.open.example;
  
  import java.io.IOException;
  import java.util.ArrayList;
  import java.util.Iterator;
  import java.util.List;
  
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  
  import com.aliyun.odps.data.Record;
  import com.aliyun.odps.data.TableInfo;
  import com.aliyun.odps.mapred.JobClient;
  import com.aliyun.odps.mapred.MapperBase;
  import com.aliyun.odps.mapred.ReducerBase;
  import com.aliyun.odps.mapred.conf.JobConf;
  import com.aliyun.odps.mapred.utils.InputUtils;
  import com.aliyun.odps.mapred.utils.OutputUtils;
  import com.aliyun.odps.mapred.utils.SchemaUtils;
  
  /**
   * Join, mr_join_src1/mr_join_src2(key bigint, value string), mr_join_out(key bigint, value1 string,
   * value2 string)
   * 
   */
  public class Join {
  
    public static final Log LOG = LogFactory.getLog(Join.class);
  
    public static class JoinMapper extends MapperBase {
  
      private Record mapkey;
      private Record mapvalue;
      private long tag;
  
      @Override
      public void setup(TaskContext context) throws IOException {
        mapkey = context.createMapOutputKeyRecord();
        mapvalue = context.createMapOutputValueRecord();
        tag = context.getInputTableInfo().getLabel().equals("left") ? 0 : 1;
      }
  
      @Override
      public void map(long key, Record record, TaskContext context) throws IOException {
        mapkey.set(0, record.get(0));
        mapkey.set(1, tag);
  
        for (int i = 1; i < record.getColumnCount(); i++) {
          mapvalue.set(i - 1, record.get(i));
        }
        context.write(mapkey, mapvalue);
      }
  
    }
  
    public static class JoinReducer extends ReducerBase {
  
      private Record result = null;
  
      @Override
      public void setup(TaskContext context) throws IOException {
        result = context.createOutputRecord();
      }
  
      // reduce函数每次的输入会是key相同的所有record
      @Override
      public void reduce(Record key, Iterator<Record> values, TaskContext context) throws IOException {
        long k = key.getBigint(0);
        List<Object[]> leftValues = new ArrayList<Object[]>();
  
        // 由于设置了outputKeySortColumn是key + tag组合，这样可以保证reduce函数的输入record中，left表的record数据在前面
        while (values.hasNext()) {
          Record value = values.next();
          long tag = (Long) key.get(1);
  
          // 左表的数据会先缓存到内存中
          if (tag == 0) {
            leftValues.add(value.toArray().clone());
          } else {
            // 碰到右表的数据，会与所有左表的数据进行join输出，此时左表的数据已经全部在内存里了
            // 这个实现只是一个功能展示，性能比较低，不建议用于实际生产
            for (Object[] leftValue : leftValues) {
              int index = 0;
              result.set(index++, k);
              for (int i = 0; i < leftValue.length; i++) {
                result.set(index++, leftValue[i]);
              }
              for (int i = 0; i < value.getColumnCount(); i++) {
                result.set(index++, value.get(i));
              }
              context.write(result);
            }
          }
        }
  
      }
  
    }
  
    public static void main(String[] args) throws Exception {
      if (args.length != 3) {
        System.err.println("Usage: Join <input table1> <input table2> <out>");
        System.exit(2);
      }
      JobConf job = new JobConf();
  
      job.setMapperClass(JoinMapper.class);
      job.setReducerClass(JoinReducer.class);
  
      job.setMapOutputKeySchema(SchemaUtils.fromString("key:bigint,tag:bigint"));
      job.setMapOutputValueSchema(SchemaUtils.fromString("value:string"));
  
      job.setPartitionColumns(new String[] {"key"});
      job.setOutputKeySortColumns(new String[] {"key", "tag"});
      job.setOutputGroupingColumns(new String[] {"key"});
      job.setNumReduceTasks(1);
  
      InputUtils.addTable(TableInfo.builder().tableName(args[0]).label("left").build(), job);
      InputUtils.addTable(TableInfo.builder().tableName(args[1]).label("right").build(), job);
      OutputUtils.addTable(TableInfo.builder().tableName(args[2]).build(), job);
  
      JobClient.runJob(job);
    }
  
  }
  