[PIG-2144] ClassCastException when using IsEmpty(DIFF())

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 0.8.0, 0.8.1, 0.9.0
• Fix Version/s: 0.8.0, 0.8.1, 0.9.0
• Assignee: Thejas Nair
• Reporter: Mitesh Singh Jat
• Created: 27/Jun/11 14:23
• Updated: 04/Aug/11 00:34
• Resolved: 29/Jun/11 00:32

Description

I have following input <name>:<nickname>, for which I want to find records where name is different from nickname.

input/name_nickname.txt

Bharat:Bharat
Amita:Amita
Mitesh:Mitesh
Reenu:Anshu
Shikha:Shikhu
Shilpa:Shilpi

I have following script to find records where name is different from nickname.

isEmpty_diff.pig

A = LOAD 'input/name_nickname.txt' using PigStorage(':');

B = FILTER A BY NOT IsEmpty(DIFF($0, $1));

DUMP B;

The above pig script works with older pig versions (e.g. 0.8.0 (r1043805)) and gives following output

output of isEmpty_diff.pig

(Reenu,Anshu)
(Shikha,Shikhu)
(Shilpa,Shilpi)

However, the above pig script (isEmpty_diff.pig) fails on Pig 0.9 (e.g. 0.9.0.xx (r1127671)) and newer version of Pig 0.8 (e.g. version 0.8.0.xx (r1102885)) , with ClassCastException

ClassCastException

java.lang.ClassCastException: org.apache.pig.data.DefaultDataBag cannot be cast to java.lang.Boolean
        at org.apache.pig.backend.hadoop.executionengine.physicalLayer.expressionOperators.PONot.getNext(PONot.java:75)
        at org.apache.pig.backend.hadoop.executionengine.physicalLayer.PhysicalOperator.getNext(PhysicalOperator.java:318)
        at org.apache.pig.backend.hadoop.executionengine.physicalLayer.expressionOperators.POUserFunc.processInput(POUserFunc.java:159)
        at org.apache.pig.backend.hadoop.executionengine.physicalLayer.expressionOperators.POUserFunc.getNext(POUserFunc.java:184)
        at org.apache.pig.backend.hadoop.executionengine.physicalLayer.expressionOperators.POUserFunc.getNext(POUserFunc.java:269)
        at org.apache.pig.backend.hadoop.executionengine.physicalLayer.expressionOperators.PONot.getNext(PONot.java:71)
        at org.apache.pig.backend.hadoop.executionengine.physicalLayer.relationalOperators.POFilter.getNext(POFilter.java:148)
        at org.apache.pig.backend.hadoop.executionengine.mapReduceLayer.PigMapBase.runPipeline(PigMapBase.java:261)
        at org.apache.pig.backend.hadoop.executionengine.mapReduceLayer.PigMapBase.map(PigMapBase.java:256)
        at org.apache.pig.backend.hadoop.executionengine.mapReduceLayer.PigMapBase.map(PigMapBase.java:58)
        at org.apache.hadoop.mapreduce.Mapper.run(Mapper.java:144)
        at org.apache.hadoop.mapred.MapTask.runNewMapper(MapTask.java:676)
        at org.apache.hadoop.mapred.MapTask.run(MapTask.java:336)
        at org.apache.hadoop.mapred.LocalJobRunner$Job.run(LocalJobRunner.java:210)

As a workaround, I used the following pig script.

A = LOAD 'input/name_nickname.txt' using PigStorage(':');

--B = FILTER A BY NOT IsEmpty(DIFF($0, $1));
B1 = FOREACH A GENERATE $0, $1, DIFF($0, $1);
B2 = FILTER B1 BY NOT IsEmpty($2);
B = FOREACH B2 GENERATE $0, $1;

DUMP B;