我需要使用hbase上的mr比较hbase中的两个表（表1、表2），并将摘要写入第三个表（表3）
我正在使用下面的tablemapreduceutil psuedo代码。Map器：表1：表3。
在mapper中，我需要比较table1和table2的值。在哪里示例化表2？
在Map器中，是否必须为每个Map器示例化table3？我想为整个mapreduce作业只示例化一次table3？

driver()
{
TableMapReduceUtil.initTableMapperJob(
    table1,        // input table
    scan,              
    MyMapper.class,     // mapper class
    Text.class,         
    IntWritable.class,  
    job);
TableMapReduceUtil.initTableReducerJob(
    table3,        // output table
    MyTableReducer.class,    
    job);
}

public static class MyMapper extends TableMapper<Text, IntWritable>  {
    public static final byte[] CF = "cf".getBytes();
    public static final byte[] ATTR1 = "attr1".getBytes();

    private final IntWritable ONE = new IntWritable(1);
    private Text text = new Text();

    public void map(ImmutableBytesWritable row, Result value, Context context) throws IOException, InterruptedException {
            String val = new String(value.getValue(CF, ATTR1));
            String diff;
            //instantiate Table3 and compare with val. Do i have to instantiate for each mapper?

            text.set(diff);     

            context.write(text, ONE);
    }
}

public static class MyTableReducer extends TableReducer<Text, IntWritable, ImmutableBytesWritable>  {
    public static final byte[] CF = "cf".getBytes();
    public static final byte[] COUNT = "count".getBytes();

    public void reduce(Text key, Iterable<IntWritable> values, Context context) throws IOException, InterruptedException {
            int i = 0;
            for (IntWritable val : values) {
                i += val.get();
            }
            Put put = new Put(Bytes.toBytes(key.toString()));
            put.add(CF, COUNT, Bytes.toBytes(i));

            context.write(null, put);
    }
}