org.apache.pig.pen.util
Class PreOrderDepthFirstWalker

java.lang.Object
  org.apache.pig.newplan.PlanWalker
      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.