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https://issues.apache.org/jira/browse/PIG-4644?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Anthony Hsu reassigned PIG-4644:
--------------------------------
Assignee: Anthony Hsu
> POProject'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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