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Date: Wed, 11 Aug 2010 13:51:59 +0100
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Subject: Cardinality of ReduceCopiers to map outputs
From: Pedro Costa <psdc1978@gmail.com>
To: mapreduce-dev@hadoop.apache.org
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Hi,


1 - I would like to know if a Map Task can produce more than 1 map
output per execution?

2 - A Map Task can't be reused, right? When a Map Task instance
produced a map outputs, this instance will end, right?

3 - I would like to know if a ReduceCopier will fetch only 1 map
output at a time and saves it in a file or in memory before merging
them? For example, if we've a ReduceCopier that fetches 4 map outputs,
the reduce will save the 4 outputs in separate and only after all map
outputs are copied to the reduce side, that the ReduceCopier will
merge them, right?


Thanks,
--
Pedro


-- 
Pedro