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From Piyush Kansal <piyush.kan...@gmail.com>
Subject Re: Query regarding Hadoop Partitioning
Date Mon, 20 Feb 2012 09:12:16 GMT
Thanks Harsh. I will try it and will get back to you.

On Mon, Feb 20, 2012 at 3:55 AM, Harsh J <harsh@cloudera.com> wrote:

> I do not think you can do it out of the box with streaming, but
> last.fm's Dumbo (highly recommended if you use Python M/R) and its
> add-on Feathers libraries can do it apparently.
>
> See Erik Forsberg's detailed answer (second) on
>
> http://stackoverflow.com/questions/1626786/generating-separate-output-files-in-hadoop-streaming
> for more.
>
> On Mon, Feb 20, 2012 at 1:57 PM, Piyush Kansal <piyush.kansal@gmail.com>
> wrote:
> > Thanks for the immediate reply Harsh. I will try using it.
> >
> > By the way, cant we achieve the same goal with Hadoop Streaming (using
> > Python)?
> >
> >
> > On Mon, Feb 20, 2012 at 2:59 AM, Harsh J <harsh@cloudera.com> wrote:
> >>
> >> Piyush,
> >>
> >> Yes. Currently the partitioned data is always sorted by (and then
> >> grouped by) keys before the reduce() calls begin.
> >>
> >> On Mon, Feb 20, 2012 at 12:51 PM, Piyush Kansal <
> piyush.kansal@gmail.com>
> >> wrote:
> >> > Thanks Harsh.
> >> >
> >> > But will it also sort the data as Partitioner does.
> >> >
> >> >
> >> > On Sun, Feb 19, 2012 at 10:54 PM, Harsh J <harsh@cloudera.com> wrote:
> >> >>
> >> >> Hi,
> >> >>
> >> >> You would find it easier to use the Java API's MultipleOutputs
> (and/or
> >> >> MultipleOutputFormat, which directly works on a configured key
> field),
> >> >> to write each key-partition out in its own file.
> >> >>
> >> >> On Mon, Feb 20, 2012 at 7:38 AM, Piyush Kansal
> >> >> <piyush.kansal@gmail.com>
> >> >> wrote:
> >> >> > Hi Friends,
> >> >> >
> >> >> > I have to sort huge amount of data in minimum possible time
> probably
> >> >> > using
> >> >> > partitioning. The key is composed of 3 fields(partition, text
and
> >> >> > number).
> >> >> > This is how partition is defined:
> >> >> >
> >> >> > Partition "1" for range 1-10
> >> >> > Partition "2" for range 11-20
> >> >> > Partition "3" for range 21-30
> >> >> >
> >> >> > I/P file format: partition[tab]text[tab]range-start[tab]range-end
> >> >> >
> >> >> > [cloudera@localhost kMer2]$ cat input1
> >> >> >
> >> >> > 1 chr1 1 10
> >> >> > 1 chr1 2 8
> >> >> > 2 chr1 11 18
> >> >> >
> >> >> > [cloudera@localhost kMer2]$ cat input2
> >> >> >
> >> >> > 1 chr1 3 7
> >> >> > 2 chr1 12 19
> >> >> >
> >> >> > [cloudera@localhost kMer2]$ cat input3
> >> >> >
> >> >> > 3 chr1 22 30
> >> >> >
> >> >> > [cloudera@localhost kMer2]$ cat input4
> >> >> >
> >> >> > 3 chr1 22 30
> >> >> > 1 chr1 9 10
> >> >> > 2 chr1 15 16
> >> >> >
> >> >> > Then I ran following command:
> >> >> >
> >> >> > hadoop jar
> >> >> >
> /usr/lib/hadoop/contrib/streaming/hadoop-streaming-0.20.2-cdh3u2.jar
> >> >> > \
> >> >> > -D stream.map.output.field.separator='\t' \
> >> >> > -D stream.num.map.output.key.fields=3 \
> >> >> > -D map.output.key.field.separator='\t' \
> >> >> > -D mapred.text.key.partitioner.options=-k1 \
> >> >> > -D mapred.reduce.tasks=3 \
> >> >> > -input /usr/pkansal/kMer2/ip \
> >> >> > -output /usr/pkansal/kMer2/op \
> >> >> > -mapper /home/cloudera/kMer2/kMer2Map.py \
> >> >> > -file /home/cloudera/kMer2/kMer2Map.py \
> >> >> > -reducer /home/cloudera/kMer2/kMer2Red.py \
> >> >> > -file /home/cloudera/kMer2/kMer2Red.py
> >> >> >
> >> >> > Both mapper and reducer scripts just contain one line of code:
> >> >> >
> >> >> > for line in sys.stdin:
> >> >> >     line = line.strip()
> >> >> >     print "%s" % (line)
> >> >> >
> >> >> > Following is the o/p:
> >> >> >
> >> >> > [cloudera@localhost kMer2]$ hadoop dfs -cat
> >> >> > /usr/pkansal/kMer2/op/part-00000
> >> >> >
> >> >> > 2 chr1 12 19
> >> >> > 2 chr1 15 16
> >> >> > 3 chr1 22 30
> >> >> > 3 chr1 22 30
> >> >> >
> >> >> > [cloudera@localhost kMer2]$ hadoop dfs -cat
> >> >> > /usr/pkansal/kMer2/op/part-00001
> >> >> >
> >> >> > 1 chr1 2 8
> >> >> > 1 chr1 3 7
> >> >> > 1 chr1 9 10
> >> >> > 2 chr1 11 18
> >> >> >
> >> >> > [cloudera@localhost kMer2]$ hadoop dfs -cat
> >> >> > /usr/pkansal/kMer2/op/part-00002
> >> >> >
> >> >> > 1 chr1 1 10
> >> >> > 3 chr1 22 29
> >> >> >
> >> >> > This is not the o/p which I expected. I expected all records with:
> >> >> >
> >> >> > partition 1 in one single file eg part-m-00000
> >> >> > partition 2 in one single file eg part-m-00001
> >> >> > partition 3 in one single file eg part-m-00002
> >> >> >
> >> >> > Can you please suggest if I am doing it in a right way?
> >> >> >
> >> >> > --
> >> >> > Regards,
> >> >> > Piyush Kansal
> >> >> >
> >> >>
> >> >>
> >> >>
> >> >> --
> >> >> Harsh J
> >> >> Customer Ops. Engineer
> >> >> Cloudera | http://tiny.cloudera.com/about
> >> >
> >> >
> >> >
> >> >
> >> > --
> >> > Regards,
> >> > Piyush Kansal
> >> >
> >>
> >>
> >>
> >> --
> >> Harsh J
> >> Customer Ops. Engineer
> >> Cloudera | http://tiny.cloudera.com/about
> >
> >
> >
> >
> > --
> > Regards,
> > Piyush Kansal
> >
>
>
>
> --
> Harsh J
> Customer Ops. Engineer
> Cloudera | http://tiny.cloudera.com/about
>



-- 
Regards,
Piyush Kansal

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