public class ReduceDriver<T> extends Object implements Driver<ReduceFunction<T>,T>
The ReduceDriver creates an iterator over all records from its input. The iterator returns all records grouped by their
key. The elements are handed pairwise to the reduce()
method of the ReduceFunction.
ReduceFunction
Constructor and Description |
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ReduceDriver() |
Modifier and Type | Method and Description |
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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.
|
Class<ReduceFunction<T>> |
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<ReduceFunction<T>,T> context) |
public void setup(TaskContext<ReduceFunction<T>,T> context)
setup
in interface Driver<ReduceFunction<T>,T>
public int getNumberOfInputs()
Driver
getNumberOfInputs
in interface Driver<ReduceFunction<T>,T>
public Class<ReduceFunction<T>> getStubType()
Driver
MapFunction.class
.getStubType
in interface Driver<ReduceFunction<T>,T>
public int getNumberOfDriverComparators()
Driver
getNumberOfDriverComparators
in interface Driver<ReduceFunction<T>,T>
public void prepare() throws Exception
Driver
public void run() throws Exception
Driver
public void cleanup()
Driver
cleanup
in interface Driver<ReduceFunction<T>,T>
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