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java.lang.Objectorg.apache.hadoop.mapred.lib.KeyFieldBasedPartitioner<K2,V2>
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).
| Constructor Summary | |
|---|---|
KeyFieldBasedPartitioner()
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| Method Summary | |
|---|---|
void |
configure(JobConf job)
Initializes a new instance from a JobConf. |
protected int |
getPartition(int hash,
int numReduceTasks)
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int |
getPartition(K2 key,
V2 value,
int numReduceTasks)
Get the paritition 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)
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| Methods inherited from class java.lang.Object |
|---|
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
| Constructor Detail |
|---|
public KeyFieldBasedPartitioner()
| Method Detail |
|---|
public void configure(JobConf job)
JobConfigurableJobConf.
configure in interface JobConfigurablejob - the configuration
public int getPartition(K2 key,
V2 value,
int numReduceTasks)
PartitionerTypically a hash function on a all or a subset of the key.
getPartition in interface Partitioner<K2,V2>key - the key to be paritioned.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)
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