T- Type of the elements that this function processes.
O- The type of the elements returned by the user-defined function.
@Public @FunctionalInterface public interface GroupReduceFunction<T,O> extends Function, Serializable
For a reduce functions that works incrementally by combining always two elements, see
The basic syntax for using a grouped GroupReduceFunction is as follows:
DataSet<X> input = ...; DataSet<X> result = input.groupBy(<key-definition>).reduceGroup(new MyGroupReduceFunction());
Partial computation can significantly improve the performance of a
GroupReduceFunction. This technique is also known as applying a Combiner. Implement the
GroupCombineFunction interface to enable partial computations, i.e., a combiner for this
|Modifier and Type||Method and Description|
The reduce method.
void reduce(Iterable<T> values, Collector<O> out) throws Exception
values- All records that belong to the given input key.
out- The collector to hand results to.
Exception- This method may throw exceptions. Throwing an exception will cause the operation to fail and may trigger recovery.
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