Package org.apache.hadoop.hbase.mapreduce

Class IdentityTableReducer

java.lang.Object
org.apache.hadoop.mapreduce.Reducer<KEYIN,VALUEIN,KEYOUT,Mutation>
org.apache.hadoop.hbase.mapreduce.TableReducer<org.apache.hadoop.io.Writable,Mutation,org.apache.hadoop.io.Writable>
org.apache.hadoop.hbase.mapreduce.IdentityTableReducer
@Public public class IdentityTableReducer extends TableReducer<org.apache.hadoop.io.Writable,Mutation,org.apache.hadoop.io.Writable>
Convenience class that simply writes all values (which must be Put or Delete instances) passed to it out to the configured HBase table. This works in combination with TableOutputFormat which actually does the writing to HBase.

Keys are passed along but ignored in TableOutputFormat. However, they can be used to control how your values will be divided up amongst the specified number of reducers.

You can also use the TableMapReduceUtil class to set up the two classes in one step:

TableMapReduceUtil.initTableReducerJob("table", IdentityTableReducer.class, job);
This will also set the proper TableOutputFormat which is given the table parameter. The Put or Delete define the row and columns implicitly.

  • Nested Class Summary

    Nested classes/interfaces inherited from class org.apache.hadoop.mapreduce.Reducer

    org.apache.hadoop.mapreduce.Reducer.Context

  • Field Summary

    Fields
    Modifier and Type
    Field
    Description
    private static final org.slf4j.Logger
    LOG
     

  • Constructor Summary

    Constructors
    Constructor
    Description
    IdentityTableReducer()
     

  • Method Summary

    Modifier and Type
    Method
    Description
    void
    reduce(org.apache.hadoop.io.Writable key, Iterable<Mutation> values, org.apache.hadoop.mapreduce.Reducer<org.apache.hadoop.io.Writable,Mutation,org.apache.hadoop.io.Writable,Mutation>.org.apache.hadoop.mapreduce.Reducer.Context context)
    Writes each given record, consisting of the row key and the given values, to the configured OutputFormat.

    Methods inherited from class org.apache.hadoop.mapreduce.Reducer

    cleanup, run, setup

    Methods inherited from class java.lang.Object

    clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

  • Field Details

    • LOG

      private static final org.slf4j.Logger LOG

  • Constructor Details

  • Method Details

    • reduce

      public void reduce(org.apache.hadoop.io.Writable key, Iterable<Mutation> values, org.apache.hadoop.mapreduce.Reducer<org.apache.hadoop.io.Writable,Mutation,org.apache.hadoop.io.Writable,Mutation>.org.apache.hadoop.mapreduce.Reducer.Context context) throws IOException, InterruptedException
      Writes each given record, consisting of the row key and the given values, to the configured OutputFormat. It is emitting the row key and each Put or Delete as separate pairs.
      Overrides:
      reduce in class org.apache.hadoop.mapreduce.Reducer<org.apache.hadoop.io.Writable,Mutation,org.apache.hadoop.io.Writable,Mutation>
      Parameters:
      key - The current row key.
      values - The Put or Delete list for the given row.
      context - The context of the reduce.
      Throws:
      IOException - When writing the record fails.
      InterruptedException - When the job gets interrupted.