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From Eric Sammer <esam...@cloudera.com>
Subject Re: Setting the number of mappers to 0
Date Fri, 09 Jul 2010 22:28:18 GMT

Currently there's no way to avoid the map stage and the sort and
shuffle that comes with it. The only real option is to have an
identity mapper that passes the keys / values through as you're doing

On Fri, Jul 9, 2010 at 4:07 PM, Chinni, Ravi <rchinni@syncsort.com> wrote:
> I am trying to develop a MR application. Due to the kind of application I am
> trying to develop, the mapper is a dummy (passes it’s input to it’s output)
> task and I am only interested in having a partitioner and reducer.
> The MR framework allows us to set the number of reducers to 0. Is there a
> way to set the number of mappers to 0? Basically, I want to avoid the
> overhead of creating mapper tasks and calling the map function once per
> record.
> Is it feasibly to modify the MR framework so as not the create the mapper
> tasks and have the partitioners read the input data from HDFS directly?
> Any pointers are appreciated.
> Thanks,
> Ravi Chinni
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Eric Sammer
twitter: esammer
data: www.cloudera.com

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