Is it possible that use ArrayList or other type instead Iterable when use reduce(Object,
Iterable, Context)?
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Key: MAPREDUCE-2007
URL: https://issues.apache.org/jira/browse/MAPREDUCE-2007
Project: Hadoop Map/Reduce
Issue Type: Improvement
Affects Versions: 0.20.2
Reporter: Hui Wen Han
Fix For: 0.20.2
1) Sometimes We only need get the elements count of the input values of Reducer task,
but we have to iterate all the input values to calculate it.
2) Sometimes We only need get a few elements (for example top n,last n ,or random ) from
the input values of Reducer task,
if it can use ArrayList or other type instead Iterable when use reduce(Object, Iterable,
Context),it 's more conveniency.
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