Error in Cogroup when key fields types don't match
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Key: PIG-1075
URL: https://issues.apache.org/jira/browse/PIG-1075
Project: Pig
Issue Type: Bug
Affects Versions: 0.5.0
Reporter: Ankur
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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