Package org.apache.hadoop.mapred.lib

Class KeyFieldBasedComparator<K,V>

java.lang.Object

org.apache.hadoop.io.WritableComparator

org.apache.hadoop.mapreduce.lib.partition.KeyFieldBasedComparator<K,V>

org.apache.hadoop.mapred.lib.KeyFieldBasedComparator<K,V>

All Implemented Interfaces:

Comparator, Configurable, RawComparator, JobConfigurable

@Public
@Stable
public class KeyFieldBasedComparator<K,V>
extends KeyFieldBasedComparator<K,V>
implements JobConfigurable

This comparator implementation provides a subset of the features provided by the Unix/GNU Sort. In particular, the supported features are: -n, (Sort numerically) -r, (Reverse the result of comparison) -k pos1[,pos2], where pos is of the form f[.c][opts], where f is the number of the field to use, and c is the number of the first character from the beginning of the field. Fields and character posns are numbered starting with 1; a character position of zero in pos2 indicates the field's last character. If '.c' is omitted from pos1, it defaults to 1 (the beginning of the field); if omitted from pos2, it defaults to 0 (the end of the field). opts are ordering options (any of 'nr' as described above). We assume that the fields in the key are separated by MRJobConfig.MAP_OUTPUT_KEY_FIELD_SEPARATOR

Field Summary

Fields inherited from class org.apache.hadoop.mapreduce.lib.partition.KeyFieldBasedComparator

COMPARATOR_OPTIONS

Constructor Summary

Constructors

Constructor	Description
KeyFieldBasedComparator()

Method Summary

Modifier and Type	Method	Description
void	configure(JobConf job)	Initializes a new instance from a JobConf.

Methods inherited from class org.apache.hadoop.mapreduce.lib.partition.KeyFieldBasedComparator

compare, getConf, getKeyFieldComparatorOption, setConf, setKeyFieldComparatorOptions

Methods inherited from class org.apache.hadoop.io.WritableComparator

compare, compare, compareBytes, define, get, get, getKeyClass, hashBytes, hashBytes, newKey, readDouble, readFloat, readInt, readLong, readUnsignedShort, readVInt, readVLong

Methods inherited from class java.lang.Object

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

Methods inherited from interface java.util.Comparator

equals, reversed, thenComparing, thenComparing, thenComparing, thenComparingDouble, thenComparingInt, thenComparingLong

Constructor Details

KeyFieldBasedComparator

public KeyFieldBasedComparator()

Method Details

configure

public void configure(JobConf job)

Description copied from interface: JobConfigurable

Initializes a new instance from a JobConf.

Specified by:

configure in interface JobConfigurable

Parameters:

job - the configuration