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public interface Reducer<T,R>
Reduces a list of results T from map phase of MapReduceTask. Infinispan distributed execution environment creates one instance of Reducer per execution node.
Method Summary | |
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R |
reduce(T mapResult,
R previouslyReduced)
Reduces a result T from map phase and return R. |
Method Detail |
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R reduce(T mapResult, R previouslyReduced)
Assume that on Infinispan node N, an instance of Mapper was mapped and invoked on k many key/value pairs. Each T(i) in the list of all T's returned from map phase executed on Infinispan node N is passed to reducer along with previsouly computed R(i-1). Finally the last invocation of reducer on T(k), R is returned to a distributed task that originated map/reduce request.
mapResult
- result T of map phasepreviouslyReduced
- previously accumulated reduced result
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