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https://issues.apache.org/jira/browse/PIG-1075?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Daniel Dai closed PIG-1075.
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> Error in Cogroup when key fields types don't match
> --------------------------------------------------
>
> Key: PIG-1075
> URL: https://issues.apache.org/jira/browse/PIG-1075
> Project: Pig
> Issue Type: Bug
> Affects Versions: 0.5.0
> Reporter: Ankur
> Assignee: Richard Ding
> Fix For: 0.7.0
>
> Attachments: PIG-1075.patch
>
>
> When Cogrouping 2 relations on multiple key fields, pig throws an error if
> the corresponding types don't match.
> Consider the following script:-
> A = LOAD 'data' USING PigStorage() as (a:chararray, b:int, c:int);
> B = LOAD 'data' USING PigStorage() as (a:chararray, b:chararray, c:int);
> C = CoGROUP A BY (a,b,c), B BY (a,b,c);
> D = FOREACH C GENERATE FLATTEN(A), FLATTEN(B);
> describe D;
> dump D;
> The complete stack trace of the error thrown is
> Pig Stack Trace
> ---------------
> ERROR 1051: Cannot cast to Unknown
> org.apache.pig.impl.logicalLayer.FrontendException: ERROR 1001: Unable to
> describe schema for alias D
> at org.apache.pig.PigServer.dumpSchema(PigServer.java:436)
> at
> org.apache.pig.tools.grunt.GruntParser.processDescribe(GruntParser.java:233)
> at
> org.apache.pig.tools.pigscript.parser.PigScriptParser.parse(PigScriptParser.java:253)
> at
> org.apache.pig.tools.grunt.GruntParser.parseStopOnError(GruntParser.java:168)
> at
> org.apache.pig.tools.grunt.GruntParser.parseStopOnError(GruntParser.java:144)
> at org.apache.pig.tools.grunt.Grunt.exec(Grunt.java:89)
> at org.apache.pig.Main.main(Main.java:397)
> Caused by: org.apache.pig.impl.plan.PlanValidationException: ERROR 0: An
> unexpected exception caused the validation to stop
> at
> org.apache.pig.impl.plan.PlanValidator.validateSkipCollectException(PlanValidator.java:104)
> at
> org.apache.pig.impl.logicalLayer.validators.TypeCheckingValidator.validate(TypeCheckingValidator.java:40)
> at
> org.apache.pig.impl.logicalLayer.validators.TypeCheckingValidator.validate(TypeCheckingValidator.java:30)
> at
> org.apache.pig.impl.logicalLayer.validators.LogicalPlanValidationExecutor.validate(LogicalPlanValidationExecutor.java:83)
> at org.apache.pig.PigServer.compileLp(PigServer.java:821)
> at org.apache.pig.PigServer.dumpSchema(PigServer.java:428)
> ... 6 more
> Caused by: org.apache.pig.impl.logicalLayer.validators.TypeCheckerException:
> ERROR 1060: Cannot resolve COGroup output schema
> at
> org.apache.pig.impl.logicalLayer.validators.TypeCheckingVisitor.visit(TypeCheckingVisitor.java:2463)
> at
> org.apache.pig.impl.logicalLayer.LOCogroup.visit(LOCogroup.java:372)
> at org.apache.pig.impl.logicalLayer.LOCogroup.visit(LOCogroup.java:45)
> at
> org.apache.pig.impl.plan.DependencyOrderWalker.walk(DependencyOrderWalker.java:69)
> at org.apache.pig.impl.plan.PlanVisitor.visit(PlanVisitor.java:51)
> at
> org.apache.pig.impl.plan.PlanValidator.validateSkipCollectException(PlanValidator.java:101)
> ... 11 more
> Caused by: org.apache.pig.impl.logicalLayer.validators.TypeCheckerException:
> ERROR 1051: Cannot cast to Unknown
> at
> org.apache.pig.impl.logicalLayer.validators.TypeCheckingVisitor.insertAtomicCastForCOGroupInnerPlan(TypeCheckingVisitor.java:2552)
> at
> org.apache.pig.impl.logicalLayer.validators.TypeCheckingVisitor.visit(TypeCheckingVisitor.java:2451)
> ... 16 more
> The error message does not help the user in identifying the issue clearly
> especially if the pig script is large and complex.
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