org.apache.hadoop.mapred.lib

类 KeyFieldBasedComparator<K,V>

java.lang.Object

org.apache.hadoop.io.WritableComparator

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

所有已实现的接口:

Comparator, RawComparator, JobConfigurable

public class KeyFieldBasedComparator<K,V>
extends WritableComparator
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 map.output.key.field.separator.

构造器概要

构造器

构造器和说明
KeyFieldBasedComparator()

方法概要

方法

限定符和类型	方法和说明
int	compare(byte[] b1, int s1, int l1, byte[] b2, int s2, int l2) Optimization hook.
void	configure(JobConf job) Initializes a new instance from a JobConf.

从类继承的方法 org.apache.hadoop.io.WritableComparator

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

从类继承的方法 java.lang.Object

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

从接口继承的方法 java.util.Comparator

equals

构造器详细资料

KeyFieldBasedComparator

public KeyFieldBasedComparator()

方法详细资料

configure

public void configure(JobConf job)

从接口复制的说明: JobConfigurable

Initializes a new instance from a JobConf.

指定者:

configure 在接口中 JobConfigurable

参数:

job - the configuration

compare

public int compare(byte[] b1,
          int s1,
          int l1,
          byte[] b2,
          int s2,
          int l2)

从类复制的说明: WritableComparator

Optimization hook. Override this to make SequenceFile.Sorter's scream.

The default implementation reads the data into two WritableComparables (using Writable.readFields(DataInput), then calls WritableComparator.compare(WritableComparable,WritableComparable).

指定者:

compare 在接口中 RawComparator

覆盖:

compare 在类中 WritableComparator