java.lang.Object
- org.apache.flink.runtime.operators.GroupReduceCombineDriver<IN,OUT>

Type Parameters:

IN - The data type consumed by the combiner.

OUT - The data type produced by the combiner.

All Implemented Interfaces:

Driver<GroupCombineFunction<IN,OUT>,OUT>
```
public class GroupReduceCombineDriver<IN,OUT>
extends Object
implements Driver<GroupCombineFunction<IN,OUT>,OUT>
```
Non-chained combine driver which is used for a CombineGroup transformation or a GroupReduce transformation where the user supplied a RichGroupReduceFunction with a combine method. The combining is performed in memory with a lazy approach which only combines elements which currently fit in the sorter. This may lead to a partial solution. In the case of the RichGroupReduceFunction this partial result is transformed into a proper deterministic result. The CombineGroup uses the GroupCombineFunction interface which allows to combine values of type IN to any type of type OUT. In contrast, the RichGroupReduceFunction requires the combine method to have the same input and output type to be able to reduce the elements after the combine from IN to OUT.
The GroupReduceCombineDriver uses a combining iterator over its input. The output of the iterator is emitted.

Constructor Summary

Constructors
Constructor Description

GroupReduceCombineDriver()

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`void`	`cancel()`	This method is invoked when the driver must aborted in mid processing.
`void`	`cleanup()`	This method is invoked in any case (clean termination and exception) at the end of the tasks operation.
`int`	`getNumberOfDriverComparators()`	Gets the number of comparators required for this driver.
`int`	`getNumberOfInputs()`	Gets the number of inputs that the task has.
`long`	`getOversizedRecordCount()`	Gets the number of oversized records handled by this combiner.
`Class<GroupCombineFunction<IN,OUT>>`	`getStubType()`	Gets the class of the stub type that is run by this task.
`void`	`prepare()`	This method is called before the user code is opened.
`void`	`run()`	The main operation method of the task.
`void`	`setup(TaskContext<GroupCombineFunction<IN,OUT>,OUT> context)`

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Constructor Detail
  - GroupReduceCombineDriver
```
public GroupReduceCombineDriver()
```
- Method Detail
  - setup
```
public void setup(TaskContext<GroupCombineFunction<IN,OUT>,OUT> context)
```
    Specified by:
    
    setup in interface Driver<IN,OUT>
  - getNumberOfInputs
```
public int getNumberOfInputs()
```
    Description copied from interface: Driver
    
    Gets the number of inputs that the task has.
    
    Specified by:
    
    getNumberOfInputs in interface Driver<IN,OUT>
    
    Returns:
    
    The number of inputs.
  - getStubType
```
public Class<GroupCombineFunction<IN,OUT>> getStubType()
```
    Description copied from interface: Driver
    
    Gets the class of the stub type that is run by this task. For example, a MapTask should return MapFunction.class.
    
    Specified by:
    
    getStubType in interface Driver<IN,OUT>
    
    Returns:
    
    The class of the stub type run by the task.
  - getNumberOfDriverComparators
```
public int getNumberOfDriverComparators()
```
    Description copied from interface: Driver
    
    Gets the number of comparators required for this driver.
    
    Specified by:
    
    getNumberOfDriverComparators in interface Driver<IN,OUT>
    
    Returns:
    
    The number of comparators required for this driver.
  - prepare
```
public void prepare()
             throws Exception
```
    Description copied from interface: Driver
    
    This method is called before the user code is opened. An exception thrown by this method signals failure of the task.
    
    Specified by:
    
    prepare in interface Driver<IN,OUT>
    
    Throws:
    
    Exception - Exceptions may be forwarded and signal task failure.
  - run
```
public void run()
         throws Exception
```
    Description copied from interface: Driver
    
    The main operation method of the task. It should call the user code with the data subsets until the input is depleted.
    
    Specified by:
    
    run in interface Driver<IN,OUT>
    
    Throws:
    
    Exception - Any exception thrown by this method signals task failure. Because exceptions in the user code typically signal situations where this instance in unable to proceed, exceptions from the user code should be forwarded.
  - cleanup
```
public void cleanup()
             throws Exception
```
    Description copied from interface: Driver
    
    This method is invoked in any case (clean termination and exception) at the end of the tasks operation.
    
    Specified by:
    
    cleanup in interface Driver<IN,OUT>
    
    Throws:
    
    Exception - Exceptions may be forwarded.
  - cancel
```
public void cancel()
```
    Description copied from interface: Driver
    
    This method is invoked when the driver must aborted in mid processing. It is invoked asynchronously by a different thread.
    
    Specified by:
    
    cancel in interface Driver<IN,OUT>
  - getOversizedRecordCount
```
public long getOversizedRecordCount()
```
    Gets the number of oversized records handled by this combiner.
    
    Returns:
    
    The number of oversized records handled by this combiner.

Class GroupReduceCombineDriver<IN,​OUT>

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Constructor Detail

GroupReduceCombineDriver

Method Detail

setup

getNumberOfInputs

getStubType

getNumberOfDriverComparators

prepare

run

cleanup

cancel

getOversizedRecordCount

Class GroupReduceCombineDriver<IN,OUT>