-Re: Does HBase supports parallel table scan if I use MapReduce
yonghu 2013-08-21, 08:08
Thanks. So, to scan the table just using the java program without using
MapReduce will heavily decrease the performance.
On Tue, Aug 20, 2013 at 6:02 PM, Jeff Kolesky <[EMAIL PROTECTED]> 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.
> On Tue, Aug 20, 2013 at 8:45 AM, yonghu <[EMAIL PROTECTED]> wrote:
> > Hello,
> > I know if I use default scan api, HBase scans table in a serial manner,
> > 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