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Posted to dev@hive.apache.org by Alexis De La Cruz Toledo <al...@gmail.com> on 2012/04/13 01:54:39 UTC

Why a GroupBYOperator is realized in two MapReduce?

Hi! I have a doubt, Why a GroupBy Operator is solved
in two MapReduce Job.
1. First the aggregation functions(sum(), count(), avg(), max(), etc) are
solved partial
2. After in another MapReduce Job the aggregation function is final.
Why?

Thanks.
Regards


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