org.apache.hadoop.mapreduce.lib.partition

类 KeyFieldBasedPartitioner<K2,V2>

java.lang.Object

org.apache.hadoop.mapreduce.Partitioner<K2,V2>

org.apache.hadoop.mapreduce.lib.partition.KeyFieldBasedPartitioner<K2,V2>

所有已实现的接口:

Configurable

@InterfaceAudience.Public
@InterfaceStability.Stable
public class KeyFieldBasedPartitioner<K2,V2>
extends Partitioner<K2,V2>
implements Configurable

Defines a way to partition keys based on certain key fields (also see KeyFieldBasedComparator. The key specification supported is of the form -k pos1[,pos2], where, pos is of the form f[.c][opts], where f is the number of the key 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).

字段概要

字段

限定符和类型	字段和说明
static String	PARTITIONER_OPTIONS

构造器概要

构造器

构造器和说明
KeyFieldBasedPartitioner()

方法概要

方法

限定符和类型	方法和说明
Configuration	getConf() Return the configuration used by this object.
String	getKeyFieldPartitionerOption(JobContext job) Get the KeyFieldBasedPartitioner options
protected int	getPartition(int hash, int numReduceTasks)
int	getPartition(K2 key, V2 value, int numReduceTasks) Get the partition number for a given key (hence record) given the total number of partitions i.e. number of reduce-tasks for the job.
protected int	hashCode(byte[] b, int start, int end, int currentHash)
void	setConf(Configuration conf) Set the configuration to be used by this object.
void	setKeyFieldPartitionerOptions(Job job, String keySpec) Set the KeyFieldBasedPartitioner options used for Partitioner

从类继承的方法 java.lang.Object

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

字段详细资料

PARTITIONER_OPTIONS

public static String PARTITIONER_OPTIONS

构造器详细资料

KeyFieldBasedPartitioner

public KeyFieldBasedPartitioner()

方法详细资料

setConf

public void setConf(Configuration conf)

从接口复制的说明: Configurable

Set the configuration to be used by this object.

指定者:

setConf 在接口中 Configurable

getConf

public Configuration getConf()

从接口复制的说明: Configurable

Return the configuration used by this object.

指定者:

getConf 在接口中 Configurable

getPartition

public int getPartition(K2 key,
               V2 value,
               int numReduceTasks)

从类复制的说明: Partitioner

Get the partition number for a given key (hence record) given the total number of partitions i.e. number of reduce-tasks for the job.

Typically a hash function on a all or a subset of the key.

指定者:

getPartition 在类中 Partitioner<K2,V2>

参数:

key - the key to be partioned.

value - the entry value.

numReduceTasks - the total number of partitions.

返回:

the partition number for the key.

hashCode

protected int hashCode(byte[] b,
           int start,
           int end,
           int currentHash)

getPartition

protected int getPartition(int hash,
               int numReduceTasks)

setKeyFieldPartitionerOptions

public void setKeyFieldPartitionerOptions(Job job,
                                 String keySpec)

Set the KeyFieldBasedPartitioner options used for Partitioner

参数:

keySpec - the key specification of the form -k pos1[,pos2], where, pos is of the form f[.c][opts], where f is the number of the key 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).

getKeyFieldPartitionerOption

public String getKeyFieldPartitionerOption(JobContext job)

Get the KeyFieldBasedPartitioner options