[PIG-2739] PyList should map to Bag automatically in Jython

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 0.10.0, 0.11
• Fix Version/s: 0.11, 0.10.1
• Component/s: impl
• Hadoop Flags: Reviewed
• Assignee: Daniel Dai
• Reporter: Daniel Dai
• Created: 04/Jun/12 23:06
• Updated: 06/Jan/13 23:57
• Resolved: 06/Jun/12 05:10

Description

The following script does not work:

register 'util.py' using jython as util;
A = load '1.txt' as (sentence:chararray);
B = foreach A generate flatten(util.tokenize(sentence));
dump B;

util.py

outputSchema("words:{(word:chararray)}")
def tokenize(sentence):
    return sentence.split(' ')

Error message:
org.apache.pig.backend.executionengine.ExecException: ERROR 2078: Caught error from UDF: org.apache.pig.scripting.jython.JythonFunction [Error executing function]
at org.apache.pig.backend.hadoop.executionengine.physicalLayer.expressionOperators.POUserFunc.getNext(POUserFunc.java:288)
at org.apache.pig.backend.hadoop.executionengine.physicalLayer.expressionOperators.POUserFunc.getNext(POUserFunc.java:304)
at org.apache.pig.backend.hadoop.executionengine.physicalLayer.PhysicalOperator.getNext(PhysicalOperator.java:332)
at org.apache.pig.backend.hadoop.executionengine.physicalLayer.relationalOperators.POForEach.processPlan(POForEach.java:353)
at org.apache.pig.backend.hadoop.executionengine.physicalLayer.relationalOperators.POForEach.getNext(POForEach.java:294)
at org.apache.pig.backend.hadoop.executionengine.mapReduceLayer.PigGenericMapBase.runPipeline(PigGenericMapBase.java:273)
at org.apache.pig.backend.hadoop.executionengine.mapReduceLayer.PigGenericMapBase.map(PigGenericMapBase.java:268)
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:764)
at org.apache.hadoop.mapred.MapTask.run(MapTask.java:370)
at org.apache.hadoop.mapred.LocalJobRunner$Job.run(LocalJobRunner.java:212)
Caused by: java.io.IOException: Error executing function
at org.apache.pig.scripting.jython.JythonFunction.exec(JythonFunction.java:122)
at org.apache.pig.backend.hadoop.executionengine.physicalLayer.expressionOperators.POUserFunc.getNext(POUserFunc.java:262)
... 11 more
Caused by: org.apache.pig.backend.executionengine.ExecException: ERROR 0: Cannot convert jython type (org.python.core.PyList) to pig datatype java.lang.ClassCastException: java.lang.String cannot be cast to org.apache.pig.data.Tuple
at org.apache.pig.scripting.jython.JythonUtils.pythonToPig(JythonUtils.java:113)
at org.apache.pig.scripting.jython.JythonFunction.exec(JythonFunction.java:117)
... 12 more
Caused by: java.lang.ClassCastException: java.lang.String cannot be cast to org.apache.pig.data.Tuple
at org.apache.pig.scripting.jython.JythonUtils.pythonToPig(JythonUtils.java:69)
... 13 more

The problem is Pig expects a tuple inside a list, which is unintuitive in Python.