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java.lang.Objectorg.apache.hadoop.mapreduce.Partitioner<K2,V2>
org.apache.hadoop.mapreduce.lib.partition.KeyFieldBasedPartitioner<K2,V2>
@InterfaceAudience.Public @InterfaceStability.Stable public class KeyFieldBasedPartitioner<K2,V2>
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).
| Field Summary | |
|---|---|
static String |
PARTITIONER_OPTIONS
|
| Constructor Summary | |
|---|---|
KeyFieldBasedPartitioner()
|
|
| Method Summary | |
|---|---|
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. |
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 |
| Methods inherited from class java.lang.Object |
|---|
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
| Field Detail |
|---|
public static String PARTITIONER_OPTIONS
| Constructor Detail |
|---|
public KeyFieldBasedPartitioner()
| Method Detail |
|---|
public void setConf(Configuration conf)
Configurable
setConf in interface Configurablepublic Configuration getConf()
Configurable
getConf in interface Configurable
public int getPartition(K2 key,
V2 value,
int numReduceTasks)
PartitionerTypically a hash function on a all or a subset of the key.
getPartition in class Partitioner<K2,V2>key - the key to be partioned.value - the entry value.numReduceTasks - the total number of partitions.
key.
protected int hashCode(byte[] b,
int start,
int end,
int currentHash)
protected int getPartition(int hash,
int numReduceTasks)
public void setKeyFieldPartitionerOptions(Job job,
String keySpec)
KeyFieldBasedPartitioner options used for
Partitioner
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).public String getKeyFieldPartitionerOption(JobContext job)
KeyFieldBasedPartitioner options
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