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Date: Wed, 21 Aug 2013 10:08:08 +0200
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Subject: Re: Does HBase supports parallel table scan if I use MapReduce
From: yonghu <yongyong313@gmail.com>
To: user@hbase.apache.org
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Thanks. So, to scan the table just using the java program without using
MapReduce will heavily decrease the performance.

Yong


On Tue, Aug 20, 2013 at 6:02 PM, Jeff Kolesky <jeff@opower.com> wrote:

> The scan will be broken up into multiple map tasks, each of which will run
> over a single split of the table (look at TableInputFormat to see how it is
> done).  The map tasks will run in parallel.
>
> Jeff
>
>
> On Tue, Aug 20, 2013 at 8:45 AM, yonghu <yongyong313@gmail.com> wrote:
>
> > Hello,
> >
> > I know if I use default scan api, HBase scans table in a serial manner,
> as
> > it needs to guarantee the order of the returned tuples. My question is
> if I
> > use MapReduce to read the HBase table, and directly output the results in
> > HDFS, not returned back to client. The HBase scan is still in a serial
> > manner or in this situation it can run a parallel scan.
> >
> > Thanks!
> >
> > Yong
> >
>
>
>
> --
> *Jeff Kolesky*
> Chief Software Architect
> *Opower*
>

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