IN
- The data type consumed by the combiner.OUT
- The data type produced by the combiner.public class GroupReduceCombineDriver<IN,OUT> extends Object implements Driver<GroupCombineFunction<IN,OUT>,OUT>
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 and Description |
---|
GroupReduceCombineDriver() |
Modifier and Type | Method and 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) |
public void setup(TaskContext<GroupCombineFunction<IN,OUT>,OUT> context)
public int getNumberOfInputs()
Driver
getNumberOfInputs
in interface Driver<GroupCombineFunction<IN,OUT>,OUT>
public Class<GroupCombineFunction<IN,OUT>> getStubType()
Driver
MapFunction.class
.getStubType
in interface Driver<GroupCombineFunction<IN,OUT>,OUT>
public int getNumberOfDriverComparators()
Driver
getNumberOfDriverComparators
in interface Driver<GroupCombineFunction<IN,OUT>,OUT>
public void prepare() throws Exception
Driver
public void run() throws Exception
Driver
run
in interface Driver<GroupCombineFunction<IN,OUT>,OUT>
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.public void cleanup() throws Exception
Driver
public void cancel()
Driver
public long getOversizedRecordCount()
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