Hi Abhinav,
Thanks a lot for the valuable response..Actually I was thinking of
doing the same thing, but being new to Pig I thought of asking it on
the mailing list first..As far as the data is concerned, second column
will always be in ascending order.But I don't think it will be of any
help..I think whatever you have suggested here would be the
appropriate solution..Although I would like to ask you one thing..Is
it feasible to add that first column having count in my pig script or
do I have to change the data in my Hbase table itself???If yes then
how can I achieve it in my script??Many thanks.
Regards,
Mohammad Tariq
On Tue, May 22, 2012 at 1:16 AM, Abhinav Neelam <abhinavroc...@gmail.com> wrote:
> Hey Mohammad,
>
> You need to have sorting requirements when you say 'top 5' records. Because
> relations/bags in Pig are unordered, it's natural to ask: 'top 5 by what
> parameter?' I'm unfamiliar with HBase, but if your data in HBase has an
> implicit ordering with say an auto-increment primary key, or an explicit
> one, you could include that field in your input to Pig and then apply TOP
> on that field.
>
> Having said that, if I understand your problem correctly, you don't need
> TOP at all - you just want to process your input in groups of 5 tuples at a
> time. Again, I can't think of a way of doing this without modifying your
> input. For example, if your input included an extra field like this:
> 1 18.98 2000 1.21 193.46 2.64 58.17
> 1 52.49 2000.5 4.32 947.11 2.74 64.45
> 1 115.24 2001 16.8 878.58 2.66 94.49
> 1 55.55 2001.5 33.03 656.56 2.82 60.76
> 1 156.14 2002 35.52 83.75 2.6 59.57
> 2 138.77 2002.5 21.51 105.76 2.62 85.89
> 2 71.89 2003 27.79 709.01 2.63 85.44
> 2 59.84 2003.5 32.1 444.82 2.72 70.8
> 2 103.18 2004 4.09 413.15 2.8 54.37
>
> you could do a group on that field and proceed. Even if you had a field
> like 'line number' or 'record number' in your input, you could still
> manipulate that field (say through integer division by 5) to use it for
> grouping. In any case, you need something to let Pig bring together your 5
> tuple groups.
>
> B = group A by $0;
> C = FOREACH B { <do some processing on your 5 tuple bag A> ...
>
> Thanks,
> Abhinav
>
> On 21 May 2012 23:03, Mohammad Tariq <donta...@gmail.com> wrote:
>
>> Hi Ruslan,
>>
>> Thanks for the response.I think I have made a mistake.Actually I
>> just want the top 5 records each time.I don't have any sorting
>> requirements.
>>
>> Regards,
>> Mohammad Tariq
>>
>>
>> On Mon, May 21, 2012 at 9:31 PM, Ruslan Al-fakikh
>> <ruslan.al-fak...@jalent.ru> wrote:
>> > Hey Mohammad,
>> >
>> > Here
>> > c = TOP(5,3,a);
>> > you say: take 5 records out of a that have the biggest values in the
>> third
>> > column. Do you really need that sorting by the third column?
>> >
>> > -----Original Message-----
>> > From: Mohammad Tariq [mailto:donta...@gmail.com]
>> > Sent: Monday, May 21, 2012 3:54 PM
>> > To: user@pig.apache.org
>> > Subject: How to use TOP?
>> >
>> > Hello list,
>> >
>> > I have an Hdfs file that has 6 columns that contain some data stored in
>> an
>> > Hbase table.the data looks like this -
>> >
>> > 18.98 2000 1.21 193.46 2.64 58.17
>> > 52.49 2000.5 4.32 947.11 2.74 64.45
>> > 115.24 2001 16.8 878.58 2.66 94.49
>> > 55.55 2001.5 33.03 656.56 2.82 60.76
>> > 156.14 2002 35.52 83.75 2.6 59.57
>> > 138.77 2002.5 21.51 105.76 2.62 85.89
>> > 71.89 2003 27.79 709.01 2.63 85.44
>> > 59.84 2003.5 32.1 444.82 2.72 70.8
>> > 103.18 2004 4.09 413.15 2.8 54.37
>> >
>> > Now I have to take each record along with its next 4 records and do some
>> > processing(for example, in the first shot I have to take records 1-5, in
>> the
>> > next shot I have to take 2-6 and so on)..I am trying to use TOP for this,
>> > but getting the following error -
>> >
>> > 2012-05-21 17:04:30,328 [main] ERROR org.apache.pig.tools.grunt.Grunt
>> > - ERROR 1200: Pig script failed to parse:
>> > <line 6, column 37> Invalid scalar projection: parameters : A column
>> needs
>> > to be projected from a relation for it to be used as a scalar Details at
>> > logfile: /home/mohammad/pig-0.9.2/logs/pig_1337599211281.log
>> >
>> > I am using following commands -
>> >
>> > grunt> a = load 'hbase://logdata'
>> >>> using org.apache.pig.backend.hadoop.hbase.HBaseStorage(
>> >>> 'cf:DGR cf:HD cf:POR cf:RES cf:RHOB cf:SON', '-loadKey true') as (id,
>> >>> DGR, HD, POR, RES, RHOB, SON);
>> > grunt> b = foreach a { c = TOP(5,3,a);
>> >>> generate flatten(c);
>> >>> }
>> >
>> > Could anyone tell me how to achieve that????Many thanks.
>> >
>> > Regards,
>> > Mohammad Tariq
>> >
>>
>
>
>
> --
> Hacking is, and always has been, the Holy
> Grail of computer science.
