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From Doug Meil <doug.m...@explorysmedical.com>
Subject Re: Reading in parallel from table's regions in MapReduce
Date Tue, 04 Sep 2012 15:32:14 GMT

Hi there-

Yes, there is an input split for each region of the source table of a MR

There is a blurb on that in the RefGuide...


On 9/4/12 11:17 AM, "Ioakim Perros" <imperros@gmail.com> wrote:

>I would be grateful if someone could shed a light to the following:
>Each M/R map task is reading data from a separate region of a table.
> From the jobtracker 's GUI, at the map completion graph, I notice that
>although data read from mappers are different, they read data
>sequentially - like the table has a lock that permits only one mapper to
>read data from every region at a time.
>Does this "lock" hypothesis make sense? Is there any way I could avoid
>this useless delay?
>Thanks in advance and regards,

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