org.apache.hadoop.hive.ql.exec.mr

Class ExecReducer

java.lang.Object

MapReduceBase

org.apache.hadoop.hive.ql.exec.mr.ExecReducer

public class ExecReducer
extends MapReduceBase

ExecReducer is the generic Reducer class for Hive. Together with ExecMapper it is the bridge between the map-reduce framework and the Hive operator pipeline at execution time. It's main responsabilities are: - Load and setup the operator pipeline from XML - Run the pipeline by transforming key, value pairs to records and forwarding them to the operators - Sending start and end group messages to separate records with same key from one another - Catch and handle errors during execution of the operators.

Field Summary

Fields

Modifier and Type	Field and Description
static org.apache.commons.logging.Log	l4j

Constructor Summary

Constructors

Constructor and Description
ExecReducer()

Method Summary

Modifier and Type	Method and Description
void	close()
void	configure(JobConf job)
void	reduce(java.lang.Object key, java.util.Iterator values, OutputCollector output, Reporter reporter)

Methods inherited from class java.lang.Object

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

Field Detail

l4j

public static final org.apache.commons.logging.Log l4j

Constructor Detail

ExecReducer

public ExecReducer()

Method Detail

configure

public void configure(JobConf job)

reduce

public void reduce(java.lang.Object key,
                   java.util.Iterator values,
                   OutputCollector output,
                   Reporter reporter)
            throws java.io.IOException

Throws:

java.io.IOException

close

public void close()