@InterfaceAudience.Public @InterfaceStability.Stable public abstract class Partitioner<KEY,VALUE> extends Object
Partitioner controls the partitioning of the keys of the 
 intermediate map-outputs. The key (or a subset of the key) is used to derive
 the partition, typically by a hash function. The total number of partitions
 is the same as the number of reduce tasks for the job. Hence this controls
 which of the m reduce tasks the intermediate key (and hence the 
 record) is sent for reduction.
Note: A Partitioner is created only when there are multiple
 reducers.
Note: If you require your Partitioner class to obtain the Job's
 configuration object, implement the Configurable interface.
Reducer| Constructor and Description | 
|---|
| Partitioner() | 
| Modifier and Type | Method and Description | 
|---|---|
| abstract int | getPartition(KEY key,
            VALUE value,
            int numPartitions)Get the partition number for a given key (hence record) given the total 
 number of partitions i.e. | 
public abstract int getPartition(KEY key, VALUE value, int numPartitions)
Typically a hash function on a all or a subset of the key.
key - the key to be partioned.value - the entry value.numPartitions - the total number of partitions.key.Copyright © 2023 Apache Software Foundation. All rights reserved.