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Pig, mail # user - FLATTEN(bag_of_tuples) error in 0.8.1 ?


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Re: FLATTEN(bag_of_tuples) error in 0.8.1 ?
Yang 2012-07-18, 23:52
this actually caused a rather nasty bug today.
in another udf that returns a bag of tuples, originally I inserted the
tuple into a fieldschema inside the bag,
and the schema for FLATTEN(myudf()) as

mytuple::field1, mytuple::field2,
but actually the values of all the fields are expanded into the root level,
and overwrote another field having the same value, but without the
"mytuple::" part

this is on 0.8.1
On Tue, Jul 17, 2012 at 11:25 PM, Jonathan Coveney <[EMAIL PROTECTED]>wrote:

> In 0.10 you should have to have bag -> tuple -> elments
>
> 2012/7/17 Yang <[EMAIL PROTECTED]>
>
> > ok, found the issue,
> >
> > now I do not create an explicit FieldSchema for the inside tuple Schema,
> > but directly insert the tuple schema into
> > the bag. then it works.
> >
> > this is indeed some difference between 081 and 0.10, cuz the original
> works
> > on 0.10, and the new one only works on 0.8.1
> >
> > On Tue, Jul 17, 2012 at 4:59 PM, Yang <[EMAIL PROTECTED]> wrote:
> >
> > > I created a Udf that returns a Bag of Tuples.  the syntax is all fine,
> > but
> > > when I run it in pig,
> > > Pig gives error:
> > > 2/07/17 16:51:58 INFO jvm.JvmMetrics: Cannot initialize JVM Metrics
> with
> > > processName=JobTracker, sessionId= - already initialized
> > > 12/07/17 16:51:58 WARN mapred.LocalJobRunner: job_local_0001
> > > java.lang.ClassCastException: java.lang.String cannot be cast to
> > > org.apache.pig.data.Tuple
> > > at
> > >
> >
> org.apache.pig.backend.hadoop.executionengine.physicalLayer.expressionOperators.POProject.getNext(POProject.java:392)
> > >  at
> > >
> >
> org.apache.pig.backend.hadoop.executionengine.physicalLayer.relationalOperators.POForEach.processPlan(POForEach.java:342)
> > > at
> > >
> >
> org.apache.pig.backend.hadoop.executionengine.physicalLayer.relationalOperators.POForEach.getNext(POForEach.java:290)
> > >  at
> > >
> >
> org.apache.pig.backend.hadoop.executionengine.mapReduceLayer.PigMapBase.runPipeline(PigMapBase.java:237)
> > > at
> > >
> >
> org.apache.pig.backend.hadoop.executionengine.mapReduceLayer.PigMapBase.map(PigMapBase.java:232)
> > >  at
> > >
> >
> org.apache.pig.backend.hadoop.executionengine.mapReduceLayer.PigMapBase.map(PigMapBase.java:53)
> > > at org.apache.hadoop.mapreduce.Mapper.run(Mapper.java:144)
> > >  at org.apache.hadoop.mapred.MapTask.runNewMapper(MapTask.java:621)
> > > at org.apache.hadoop.mapred.MapTask.run(MapTask.java:305)
> > >  at
> > >
> org.apache.hadoop.mapred.LocalJobRunner$Job.run(LocalJobRunner.java:177)
> > > 12/07/17 16:51:58 INFO mapReduceLayer.MapReduceLauncher: HadoopJobId:
> > > job_local_0001
> > >
> > >
> > >
> > > it looks that the returned value is wrong somehow. but I checked the
> > > outputSchema() method, and it is exactly the same as
> > > online docs. where am I wrong?
> > > ---- this is pig 0.8.1 .       I posted a question about 1 month ago,
> > > stating that 0.8.1 FLATTEN(bag_of_tuples) behavior is different from
> > > 0.10.0, in that
> > > it keeps the enclosing tuple, while 0.10.0 strips it and places the
> > fields
> > > at the root level.
> > >
> > >
> > >
> > > Thanks!
> > > yang
> > >
> > > ///// DemoUdf.java
> > >
> > > import java.io.IOException;
> > >
> > > import org.apache.pig.EvalFunc;
> > > import org.apache.pig.data.DataBag;
> > > import org.apache.pig.data.DataType;
> > > import org.apache.pig.data.DefaultDataBag;
> > > import org.apache.pig.data.DefaultTuple;
> > > import org.apache.pig.data.Tuple;
> > > import org.apache.pig.impl.logicalLayer.FrontendException;
> > > import org.apache.pig.impl.logicalLayer.schema.Schema;
> > >
> > > public class DemoUdf  extends EvalFunc<DataBag> {
> > >
> > >  @Override
> > > public DataBag exec(Tuple args) throws IOException {
> > >
> > >  Tuple t1 = new DefaultTuple();
> > > t1.append("xx");
> > > t1.append("yy");
> > >  Tuple t2 = new DefaultTuple();
> > > t2.append("xxx");
> > >  t2.append("yyy");
> > >  DataBag b = new DefaultDataBag();
> > >  b.add(t1);
> > > b.add(t2);
> > > return b;