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https://issues.apache.org/jira/browse/PIG-4644?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
 ]

Anthony Hsu updated PIG-4644:
-----------------------------
    Summary: PORelationToExprProject's implementation of clone seems broken  
(was: POProject's implementation of clone seems broken)

> PORelationToExprProject's implementation of clone seems broken
> --------------------------------------------------------------
>
>                 Key: PIG-4644
>                 URL: https://issues.apache.org/jira/browse/PIG-4644
>             Project: Pig
>          Issue Type: Bug
>            Reporter: Ratandeep Ratti
>            Assignee: Anthony Hsu
>
> We are receiving the following exception when using Pig
> {noformat}
> Caused by: java.lang.ClassCastException: 
> org.apache.pig.backend.hadoop.executionengine.physicalLayer.expressionOperators.POProject
>  cannot be cast to org.apache.pig.backend.hadoop.executionen\
> gine.physicalLayer.expressionOperators.PORelationToExprProject
>         at 
> org.apache.pig.backend.hadoop.executionengine.physicalLayer.expressionOperators.PORelationToExprProject.clone(PORelationToExprProject.java:144)
>         at 
> org.apache.pig.backend.hadoop.executionengine.physicalLayer.expressionOperators.PORelationToExprProject.clone(PORelationToExprProject.java:50)
>         at 
> org.apache.pig.backend.hadoop.executionengine.physicalLayer.plans.PhysicalPlan.clone(PhysicalPlan.java:227)
>         at 
> org.apache.pig.backend.hadoop.executionengine.physicalLayer.relationalOperators.POForEach.clone(POForEach.java:639)
>         at 
> org.apache.pig.backend.hadoop.executionengine.physicalLayer.relationalOperators.POForEach.clone(POForEach.java:53)
>         at 
> org.apache.pig.backend.hadoop.executionengine.physicalLayer.plans.PhysicalPlan.clone(PhysicalPlan.java:227)
>         at 
> org.apache.pig.backend.hadoop.executionengine.mapReduceLayer.MultiQueryOptimizer.mergeDiamondMROper(MultiQueryOptimizer.java:298)
>         at 
> org.apache.pig.backend.hadoop.executionengine.mapReduceLayer.MultiQueryOptimizer.visitMROp(MultiQueryOptimizer.java:219)
>         at 
> org.apache.pig.backend.hadoop.executionengine.mapReduceLayer.MapReduceOper.visit(MapReduceOper.java:273)
>         at 
> org.apache.pig.backend.hadoop.executionengine.mapReduceLayer.MapReduceOper.visit(MapReduceOper.java:46)
>         at 
> org.apache.pig.impl.plan.ReverseDependencyOrderWalker.walk(ReverseDependencyOrderWalker.java:71)
>         at org.apache.pig.impl.plan.PlanVisitor.visit(PlanVisitor.java:46)
>         at 
> org.apache.pig.backend.hadoop.executionengine.mapReduceLayer.MultiQueryOptimizer.visit(MultiQueryOptimizer.java:94)
>         at 
> org.apache.pig.backend.hadoop.executionengine.mapReduceLayer.MapReduceLauncher.compile(MapReduceLauncher.java:629)
>         at 
> org.apache.pig.backend.hadoop.executionengine.mapReduceLayer.MapReduceLauncher.launchPig(MapReduceLauncher.java:148)
>         at org.apache.pig.PigServer.launchPlan(PigServer.java:1264)
> {noformat}
> On further investigation it seems that POProject's clone method is 
> implemented as 
> {noformat}
>     @Override
>     public POProject clone() throws CloneNotSupportedException {
>         ArrayList<Integer> cols = new ArrayList<Integer>(columns.size());
>         // Can resuse the same Integer objects, as they are immutable
>         for (Integer i : columns) {
>             cols.add(i);
>         }
>         POProject clone = new POProject(new OperatorKey(mKey.scope,
>             NodeIdGenerator.getGenerator().getNextNodeId(mKey.scope)),
>             requestedParallelism, cols);
>         clone.cloneHelper(this);
>         clone.overloaded = overloaded;
>         clone.startCol = startCol;
>         clone.isProjectToEnd = isProjectToEnd;
>         clone.resultType = resultType;
>         return clone;
>     }
> {noformat}
> It uses a constructor to clone POProject (which break the weak rule of object 
> cloning)
> In the subclass , PORelationToExprProject implements cloneable as
> {noformat}
> @Override
>     public PORelationToExprProject clone() throws CloneNotSupportedException {
>         return (PORelationToExprProject) super.clone();
>     }
> {noformat}
> As seen from the POProject's implementation of cloneable, super.clone will 
> never be of type PORelationToExprProject,



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