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Pig, mail # user - dereferencing bag of map


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Re: dereferencing bag of map
Abhinav Neelam 2013-06-25, 13:05
Use REGEX_EXTRACT_ALL
Something like this should work (untested, please verify)

rel2 = foreach rel1 generate
FLATTEN(REGEX_EXTRACT_ALL(attributes#'md','\\{"cld":"(\\w+)","sld":"(\\w+)"\\}'))
AS (cld: chararray, sld: chararray);

Tighten up the regex appropriately.
On 24 June 2013 14:55, Suresh Saggar <[EMAIL PROTECTED]> wrote:

> *Thanks a lot* for your reply but the problem still exists. To clarify
> further the exact sequence of pig statements are shown below:
>
> REGISTER 'hdfs://hadoop-prod-master.vpc:8020/user/hdfs/libs/prod.jar';
> <<<<< *Our custom jar containing the Loader() code.*
> records_log = LOAD
> 'hdfs://hadoop-prod-master.vpc:8020/data/{prod}/{2013-06-20-11}/*' USING
> com.example.Loader() AS (date:chararray, type:chararray, attributes:[]);
> http = FILTER records_log BY type == 'm' AND attributes#'st' == 'http';
> X = FOREACH http GENERATE attributes#'md' AS metadata;
> Y = FOREACH X GENERATE FLATTEN(metadata);
>
> grunt> describe Y
> Y: {metadata: bytearray}
> grunt> describe X
> X: {metadata: bytearray}
>
> Once I dump either X or Y, both result in the same. Further I tried FLATTEN
> directly on records_log too, but no help i.e.
> Z = FOREACH records_log GENERATE FLATTEN(attributes);
>
> Similarly JsonStorage() can't be used directly as my raw data (one stored
> in HDFS) is not json, but a custom format as shown below:
> 2013-06-20-11|m|{'st':'http','md':{'cId':'a','sId':'b'}}
>
> Here our Loader() takes above raw data as input and returns the output in
> the format: (date:chararray, type:chararray, attributes:[]). Now since
> attributes#'md' is a JSON here, I'm having problems getting the 'cId' &
> 'sId' values. Hope this clarifies the context. I assume that FLATTEN
> operator couldn't 'un-nests' the  attributes#'md' as that is represented as
> {'cId':'a','sId':'b'} but not as ['cId'#'a','sId'#'b']  (map in pig) or
> {('cId'#'a'),('sId'#'b')} (bag in pig).
>
> TIA
> Ss
>
> On Fri, Jun 21, 2013 at 6:12 PM, Pradeep Gollakota <[EMAIL PROTECTED]
> >wrote:
>
> > Suresh,
> >
> > Look into using JsonStorage(). This seems to be what you're looking for.
> > http://pig.apache.org/docs/r0.10.0/func.html#jsonloadstore
> >
> >
> > On Fri, Jun 21, 2013 at 8:35 AM, Shahab Yunus <[EMAIL PROTECTED]
> > >wrote:
> >
> > > Have you tried flattening the bag first?
> > >
> > >
> > > On Fri, Jun 21, 2013 at 5:43 AM, Suresh Saggar <[EMAIL PROTECTED]> wrote:
> > >
> > > > Facing a similar challenge. Here X contains one column named
> 'metadata'
> > > of
> > > > type bytearray. But the actual content is a JSON i.e. the value of
> > > metadata
> > > > field is a JSON (keys as sId & cId) as shown below:
> > > >
> > > > grunt> describe X
> > > > X: {metadata: bytearray}
> > > >
> > > > grunt> dump X
> > > > ({"sId":"003_w","cId":"k"})
> > > > ({"sId":"001_rf","cId":"r"})
> > > > ({"sId":"001_rf","cId":"r"})
> > > > ({"sId":"004_rf","cId":"r"})
> > > >
> > > > Any idea how can I generate cId & sId as separate chararray columns?
> > TIA
> > > >
> > > > Ss
> > > >
> > > > On Tue, Jun 18, 2013 at 5:52 AM, Pradeep Gollakota <
> > [EMAIL PROTECTED]
> > > > >wrote:
> > > >
> > > > > What's the error you are seeing? What does you bag of maps look
> like?
> > > > What
> > > > > exactly is a userId? Is it a field or is it a key in the map?
> > > > >
> > > > >
> > > > > On Mon, Jun 17, 2013 at 8:18 PM, Jerry Lam <[EMAIL PROTECTED]>
> > > wrote:
> > > > >
> > > > > > Hi Pig users,
> > > > > >
> > > > > > anyone has experience in dereferencing a bag of maps? For
> instance
> > > (in
> > > > > the
> > > > > > example below), doc in the B contains maps of userId and time. I
> > want
> > > > to
> > > > > > keep only userId in C. Pig throws an exception on C. Any help is
> > > > > > appreciated.
> > > > > >
> > > > > > A = LOAD 'data' AS doc:bytearray;
> > > > > >
> > > > > > B = FOREACH A GENERATE (bag{})doc;
> > > > > >
> > > > > > -- C = FOREACH B GENERATE doc.userId; // this doesn't work.
> > > > > >
> > > > > > Best Regards,
> > > > > >
> > > >