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From Jens Scheidtmann <jens.scheidtm...@gmail.com>
Subject Re: Mapper and Reducer takes longer than usual for a HBase table aggregation task
Date Sun, 25 Aug 2013 21:36:46 GMT
Hi Pavan,


> 2. ) If my table is in the order of millions, the number of mappers is
> increased to 5.. How does Hadoop know how many mappers to run for a
> specific job?
>
> The number of input splits determines the number of mappers. Usually (in
the default case) your source is split into hdfs blocks (usually 64 MB) and
for each block, there will be a mapper.

Best regards,

Jens

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