RichGroupReduceFunction (Flink : 2.0-SNAPSHOT API)

java.lang.Object
- org.apache.flink.api.common.functions.AbstractRichFunction
- - org.apache.flink.api.common.functions.RichGroupReduceFunction<IN,OUT>

Type Parameters:

IN - Type of the elements that this function processes.

OUT - The type of the elements returned by the user-defined function.

All Implemented Interfaces:

Serializable, Function, GroupReduceFunction<IN,OUT>, RichFunction

Direct Known Subclasses:

OperatorSubtaskStateReducer
```
@Public
public abstract class RichGroupReduceFunction<IN,OUT>
extends AbstractRichFunction
implements GroupReduceFunction<IN,OUT>
```
Rich variant of the GroupReduceFunction. As a RichFunction, it gives access to the RuntimeContext and provides setup and teardown methods: RichFunction.open(OpenContext) and RichFunction.close().
Partial computation can significantly improve the performance of a RichGroupReduceFunction. This technique is also known as applying a Combiner. Implement the GroupCombineFunction interface to enable partial computation, i.e., a combiner for this RichGroupReduceFunction.

See Also:

Serialized Form

- Constructor Summary
  
  Constructors
  Constructor Description
  
  RichGroupReduceFunction()
- Method Summary
  
  All Methods Instance Methods Abstract Methods
  Modifier and Type Method Description
  
  abstract void reduce(Iterable<IN> values, Collector<OUT> out)
  The reduce method.
  - Methods inherited from class org.apache.flink.api.common.functions.AbstractRichFunction
    close, getIterationRuntimeContext, getRuntimeContext, open, setRuntimeContext
  - Methods inherited from class java.lang.Object
    clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Constructor Detail
  - RichGroupReduceFunction
```
public RichGroupReduceFunction()
```
- Method Detail
  - reduce
```
public abstract void reduce(Iterable<IN> values,
                            Collector<OUT> out)
                     throws Exception
```
    Description copied from interface: GroupReduceFunction
    
    The reduce method. The function receives one call per group of elements.
    
    Specified by:
    
    reduce in interface GroupReduceFunction<IN,OUT>
    
    Parameters:
    
    values - All records that belong to the given input key.
    
    out - The collector to hand results to.
    
    Throws:
    
    Exception - This method may throw exceptions. Throwing an exception will cause the operation to fail and may trigger recovery.