org.apache.pig.pen.util
Class PreOrderDepthFirstWalker

java.lang.Object
  extended by org.apache.pig.newplan.PlanWalker
      extended by org.apache.pig.pen.util.PreOrderDepthFirstWalker

public class PreOrderDepthFirstWalker
extends PlanWalker


Field Summary
 
Fields inherited from class org.apache.pig.newplan.PlanWalker
plan
 
Constructor Summary
PreOrderDepthFirstWalker(OperatorPlan plan)
           
 
Method Summary
 boolean getBranchFlag()
           
 void setBranchFlag()
           
 PlanWalker spawnChildWalker(OperatorPlan plan)
          Return a new instance of this same type of walker for a subplan.
 void walk(PlanVisitor visitor)
          Begin traversing the graph.
 
Methods inherited from class org.apache.pig.newplan.PlanWalker
getPlan, setPlan
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

PreOrderDepthFirstWalker

public PreOrderDepthFirstWalker(OperatorPlan plan)
Parameters:
plan - Plan for this walker to traverse.
Method Detail

setBranchFlag

public void setBranchFlag()

getBranchFlag

public boolean getBranchFlag()

walk

public void walk(PlanVisitor visitor)
          throws FrontendException
Begin traversing the graph.

Specified by:
walk in class PlanWalker
Parameters:
visitor - Visitor this walker is being used by.
Throws:
VisitorException - if an error is encountered while walking.
FrontendException

spawnChildWalker

public PlanWalker spawnChildWalker(OperatorPlan plan)
Description copied from class: PlanWalker
Return a new instance of this same type of walker for a subplan. When this method is called the same type of walker with the provided plan set as the plan, must be returned. This can then be used to walk subplans. This allows abstract visitors to clone walkers without knowning the type of walker their subclasses used.

Specified by:
spawnChildWalker in class PlanWalker
Parameters:
plan - Plan for the new walker.
Returns:
Instance of the same type of walker with plan set to plan.


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