Grokbase Groups Pig user January 2010
FAQ
Hi Scott,

It seems that the bucket number of one record is arbitrary, then I suggest
you write your own LoadFunc to load the bucket in a DataBag. This is the pig
script:

A = LOAD 'input' USING YourLoadFunc() AS
(family,channel,timeframe,gender,b:{t:(bucket)};
B = FOREACH A GENERATE family,channel,timeframe,gender, FLATTEN(b) AS
bucket;
C = GROUP B BY (family,channel,timeframe,gender, bucket);
D = FOREACH C GENERATE group,COUNT($1);

Hope it helps you


On Thu, Jan 21, 2010 at 5:38 AM, Scott wrote:

I have a question on how to handle data that I would usually store in an
array, or into a normalized child table in a database. The input data is a
set of key/value pairs where one key can be associated with multiple values
(0 to n).

Here is a sample dataset with bucket being the multi value key:


family=sports,channel=baseball,timeframe=today,gender=M,bucket=12,bucket=27,bucket=32

family=sports,channel=baseball,timeframe=today,gender=M,bucket=12,bucket=27,bucket=32,bucket=54

family=events,channel=outdoor,timeframe=weekend,gender=F,bucket=13,bucket=27,bucket=32

family=events,channel=outdoor,timeframe=weekend,gender=F,bucket=13,bucket=27,bucket=32

What I am trying to calculate is a group count on family,channel,timeframe
and bucket, where the results would be:

(sports,baseball,today,12),2
(sports,baseball,today,27),2
(sports,baseball,today,32),2
(sports,baseball,today,54),1
(events,outdoor,weekend,13),2
(events,outdoor,weekend,27),2
(events,outdoor,weekend,32),2

One approach would seem to be to store the bucket values in a separate
relation and join using a segregate key created when reading the data in.
Something like:

A = (12345,sports,baseball,today,M)
B = (32,12345)(27,12345)(12,12345)

C = JOIN A by $0, B by $1;

D = GROUP C by (family,channel,timeframe,bucket)

I am sure this method would work, but it requires generating a map/reduce
friendly segregate key on which to join the data. Is there a more direct way
to do this in pig? Also, is it possible to load more than one relation at a
time (split the data between two relations) with the LOAD statement?

Thanks,
Scott

--
Best Regards

Jeff Zhang

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postedJan 21, '10 at 1:38p
activeJan 25, '10 at 9:22p
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