The output:
({ ([c#11,d#22]),([c#33,d#44]) })
()
looks weird.
Jerry, maybe the problem is in using PigStorage. As its javadoc says:
A load function that parses a line of input into fields using a character
delimiter
So I guess this is just for simple csv lines.
But you are trying to load a complicated Map structure as it was formatted
by previous storing.
Probably you'll need to write your own Loader for this. Another hint: using
the -schema paramenter to PigStorage, but I am not sure it can help:(
Ruslan
On Wed, Apr 17, 2013 at 11:48 PM, Jerry Lam <[email protected]> wrote:
> Hi Rusian:
>
> I did a describe B followed by a dump B, the output is:
> B: {b: {()}}
>
> ({ ([c#11,d#22]),([c#33,d#44]) })
> ()
>
> but when I executed
>
> C = foreach B generate flatten(b);
>
> dump C;
>
> I got the exception again...
>
> 2013-04-17 15:47:39,933 [Thread-26] WARN
> org.apache.hadoop.mapred.LocalJobRunner - job_local_0002
> java.lang.Exception: java.lang.ClassCastException:
> org.apache.pig.data.DataByteArray cannot be cast to
> org.apache.pig.data.DataBag
> at org.apache.hadoop.mapred.LocalJobRunner$Job.run(LocalJobRunner.java:400)
> Caused by: java.lang.ClassCastException: org.apache.pig.data.DataByteArray
> cannot be cast to org.apache.pig.data.DataBag
> at
>
> org.apache.pig.backend.hadoop.executionengine.physicalLayer.expressionOperators.POProject.processInputBag(POProject.java:586)
> at
>
> org.apache.pig.backend.hadoop.executionengine.physicalLayer.expressionOperators.POProject.getNext(POProject.java:250)
> at
>
> org.apache.pig.backend.hadoop.executionengine.physicalLayer.PhysicalOperator.getNext(PhysicalOperator.java:334)
> at
>
> org.apache.pig.backend.hadoop.executionengine.physicalLayer.relationalOperators.POForEach.processPlan(POForEach.java:372)
> at
>
> org.apache.pig.backend.hadoop.executionengine.physicalLayer.relationalOperators.POForEach.getNext(POForEach.java:297)
> at
>
> org.apache.pig.backend.hadoop.executionengine.mapReduceLayer.PigGenericMapBase.runPipeline(PigGenericMapBase.java:283)
> at
>
> org.apache.pig.backend.hadoop.executionengine.mapReduceLayer.PigGenericMapBase.map(PigGenericMapBase.java:278)
> at
>
> org.apache.pig.backend.hadoop.executionengine.mapReduceLayer.PigGenericMapBase.map(PigGenericMapBase.java:64)
> at org.apache.hadoop.mapreduce.Mapper.run(Mapper.java:144)
> at org.apache.hadoop.mapred.MapTask.runNewMapper(MapTask.java:725)
> at org.apache.hadoop.mapred.MapTask.run(MapTask.java:332)
> at
>
> org.apache.hadoop.mapred.LocalJobRunner$Job$MapTaskRunnable.run(LocalJobRunner.java:232)
> at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:439)
> at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:303)
> at java.util.concurrent.FutureTask.run(FutureTask.java:138)
> at
>
> java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:895)
> at
>
> java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:918)
> at java.lang.Thread.run(Thread.java:680)
>
>
> Best Regards,
>
> Jerry
>
>
> On Wed, Apr 17, 2013 at 3:26 PM, Ruslan Al-Fakikh <[email protected]
> >wrote:
>
> > I think that before doing the FLATTEN, you should be 100% sure that your
> > cast worked properly. Can you first DESCRIBE B and then DUMP B right
> away?
> > Or probably it just can't be cast in this way. Honestly I don't know
> > exactly how it works, but here:
> > http://pig.apache.org/docs/r0.10.0/basic.html#cast
> > I see that casting from a map to a bag should produce an error.
> > Hope that helps.
> >
> >
> > On Wed, Apr 17, 2013 at 9:38 PM, Jerry Lam <[email protected]> wrote:
> >
> > > Hi Rusian:
> > >
> > > Thanks for your help. I really appreciate it. It really puzzled me.
> > >
> > > I did a "describe B", the output is "B: {b: bytearray}".
> > >
> > > I then tried to cast it as suggested, I got:
> > > B = foreach A generate document#'b' as b:{};
> > > describe B;
> > > B: {b: {()}}
> > >
> > > Then I proceed with:
> > > C = foreach B generate flatten(b);
> > >
> > > I got:
> > > 2013-04-17 13:38:04,601 [Thread-16] WARN
> > > org.apache.hadoop.mapred.LocalJobRunner - job_local_0002
> > > java.lang.Exception: java.lang.ClassCastException:
> > > org.apache.pig.data.DataByteArray cannot be cast to
> > > org.apache.pig.data.DataBag
> > > at
> > org.apache.hadoop.mapred.LocalJobRunner$Job.run(LocalJobRunner.java:400)
> > > Caused by: java.lang.ClassCastException:
> > org.apache.pig.data.DataByteArray
> > > cannot be cast to org.apache.pig.data.DataBag
> > > at
> > >
> > >
> >
> org.apache.pig.backend.hadoop.executionengine.physicalLayer.expressionOperators.POProject.processInputBag(POProject.java:586)
> > > at
> > >
> > >
> >
> org.apache.pig.backend.hadoop.executionengine.physicalLayer.expressionOperators.POProject.getNext(POProject.java:250)
> > > at
> > >
> > >
> >
> org.apache.pig.backend.hadoop.executionengine.physicalLayer.PhysicalOperator.getNext(PhysicalOperator.java:334)
> > > at
> > >
> > >
> >
> org.apache.pig.backend.hadoop.executionengine.physicalLayer.relationalOperators.POForEach.processPlan(POForEach.java:372)
> > > at
> > >
> > >
> >
> org.apache.pig.backend.hadoop.executionengine.physicalLayer.relationalOperators.POForEach.getNext(POForEach.java:297)
> > > at
> > >
> > >
> >
> org.apache.pig.backend.hadoop.executionengine.mapReduceLayer.PigGenericMapBase.runPipeline(PigGenericMapBase.java:283)
> > > at
> > >
> > >
> >
> org.apache.pig.backend.hadoop.executionengine.mapReduceLayer.PigGenericMapBase.map(PigGenericMapBase.java:278)
> > > at
> > >
> > >
> >
> org.apache.pig.backend.hadoop.executionengine.mapReduceLayer.PigGenericMapBase.map(PigGenericMapBase.java:64)
> > > at org.apache.hadoop.mapreduce.Mapper.run(Mapper.java:144)
> > > at org.apache.hadoop.mapred.MapTask.runNewMapper(MapTask.java:725)
> > > at org.apache.hadoop.mapred.MapTask.run(MapTask.java:332)
> > > at
> > >
> > >
> >
> org.apache.hadoop.mapred.LocalJobRunner$Job$MapTaskRunnable.run(LocalJobRunner.java:232)
> > > at
> > java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:439)
> > > at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:303)
> > > at java.util.concurrent.FutureTask.run(FutureTask.java:138)
> > > at
> > >
> > >
> >
> java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:895)
> > > at
> > >
> > >
> >
> java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:918)
> > > at java.lang.Thread.run(Thread.java:680)
> > >
> > > Best Regards,
> > >
> > > Jerry
> > >
> > >
> > > On Wed, Apr 17, 2013 at 1:24 PM, Ruslan Al-Fakikh <
> [email protected]
> > > >wrote:
> > >
> > > > Hey, and as for converting a map of tuples, probably i got you wrong.
> > If
> > > > you can get to every value manually withing FOREACH then I see no
> > problem
> > > > in doing so.
> > > >
> > > >
> > > > On Wed, Apr 17, 2013 at 9:22 PM, Ruslan Al-Fakikh <
> > [email protected]
> > > > >wrote:
> > > >
> > > > > I am not sure whether you can convert a map to a tuple.
> > > > > But I am curious about one thing:
> > > > > your are trying to use 'b' as a Bag, right? Because FLATTEN needs
> it
> > to
> > > > be
> > > > > a Bag I guess:
> > > > > http://pig.apache.org/docs/r0.10.0/basic.html#flatten
> > > > > But it seems that Pig thinks that b is a byte array:
> > > > > java.lang.ClassCastException: org.apache.pig.data.DataByteArray
> > cannot
> > > be
> > > > > cast to org.apache.pig.data.DataBag
> > > > > Can you do this?:
> > > > > DESCRIBE B
> > > > >
> > > > > I suppose it can look like a Bag in the output of DUMP, but I think
> > Pig
> > > > > doesn't know it is a Bag, maybe you'll need some kind of explicit
> > cast?
> > > > >
> > > > >
> > > > > On Wed, Apr 17, 2013 at 9:11 PM, Jerry Lam <[email protected]>
> > > wrote:
> > > > >
> > > > >> Hi Rusian,
> > > > >>
> > > > >> I tried to debug each step already but no luck.
> > > > >> I did a dump (dump B;) after B = foreach A generate document#'b'
> as
> > b;
> > > > >> I got {([c#11,d#22]),([c#33,d#44])}
> > > > >> but it fails when I did C = foreach B generate flatten(b);
> > > > >>
> > > > >> I don't have controls over the input. It is passed as Map of
> Maps. I
> > > > guess
> > > > >> it makes lookup easier using a map with keys.
> > > > >>
> > > > >> Can I convert map to tuple?
> > > > >>
> > > > >> Best Regards,
> > > > >>
> > > > >> Jerry
> > > > >>
> > > > >>
> > > > >>
> > > > >> On Wed, Apr 17, 2013 at 11:57 AM, Ruslan Al-Fakikh <
> > > > [email protected]
> > > > >> >wrote:
> > > > >>
> > > > >> > Hi Jerry,
> > > > >> >
> > > > >> > I would recommend to debug the issue step by step. Just after
> this
> > > > line:
> > > > >> > A = load 'data.txt' as document:[];
> > > > >> > and then right after that:
> > > > >> > DESCRIBE A;
> > > > >> > DUMP A;
> > > > >> > and so on...
> > > > >> >
> > > > >> > To be honest I haven't used maps that much. Just curious, why
> did
> > > you
> > > > >> > choose to use them? You can also use regular tuples for storing
> > the
> > > > >> > relations. Also you can store the tuples with a schema file.
> > > > >> >
> > > > >> > Ruslan
> > > > >> >
> > > > >> >
> > > > >> > On Wed, Apr 17, 2013 at 5:28 AM, Jerry Lam <
> [email protected]>
> > > > >> wrote:
> > > > >> >
> > > > >> > > Hi pig users,
> > > > >> > >
> > > > >> > > I tried to load data using PigStorage that was previously
> stored
> > > > using
> > > > >> > > PigStorage but it failed.
> > > > >> > >
> > > > >> > > Each line looks like this in the data file that is generated
> by
> > > > >> > PigStorage:
> > > > >> > > [a#hello,b#{([c#11,d#22]),([c#33,d#44])}]
> > > > >> > >
> > > > >> > > I did the following:
> > > > >> > > A = load 'data.txt' as document:[];
> > > > >> > > B = foreach A generate document#'b' as b;
> > > > >> > > C = foreach B generate flatten(b);
> > > > >> > > dump C;
> > > > >> > >
> > > > >> > > I expect to see the following output:
> > > > >> > > ([c#11,d#22])
> > > > >> > > ([c#33,d#44])
> > > > >> > >
> > > > >> > > Instead, I got:
> > > > >> > > java.lang.ClassCastException:
> org.apache.pig.data.DataByteArray
> > > > >> cannot be
> > > > >> > > cast to org.apache.pig.data.DataBag
> > > > >> > >
> > > > >> > > Anyone encounters this problem before? How can I read the data
> > > back?
> > > > >> > >
> > > > >> > > Thanks,
> > > > >> > >
> > > > >> > > Jerry
> > > > >> > >
> > > > >> >
> > > > >>
> > > > >
> > > > >
> > > >
> > >
> >
>
