org.apache.pig.newplan.optimizer

Class Transformer

java.lang.Object

org.apache.pig.newplan.optimizer.Transformer

Direct Known Subclasses:

AddForEach.AddForEachTransformer, ColumnMapKeyPrune.ColumnMapKeyPruneTransformer, ConstantCalculator.ConstantCalculatorTransformer, FilterAboveForeach.FilterAboveForEachTransformer, GroupByConstParallelSetter.GroupAllParallelSetterTransformer, LimitOptimizer.OptimizeLimitTransformer, MergeFilter.MergeFilterTransformer, MergeForEach.MergeForEachTransformer, PartitionFilterOptimizer.PartitionFilterPushDownTransformer, PushUpFilter.PushUpFilterTransformer, SplitFilter.SplitFilterTransformer, TypeCastInserter.TypeCastInserterTransformer

public abstract class Transformer
extends Object

Constructor Summary

Constructors

Constructor and Description
Transformer()

Method Summary

Methods

Modifier and Type	Method and Description
abstract boolean	check(OperatorPlan matched) check if the transform should be done.
abstract OperatorPlan	reportChanges() Report what parts of the tree were transformed.
abstract void	transform(OperatorPlan matched) Transform the tree

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

Transformer

public Transformer()

Method Detail

check

public abstract boolean check(OperatorPlan matched)
                       throws FrontendException

check if the transform should be done. If this is being called then the pattern matches, but there may be other criteria that must be met as well.

Parameters:

matched - the sub-set of the plan that matches the pattern. This subset has the same graph as the pattern, but the operators point to the same objects as the plan to be matched.

Returns:

true if the transform should be done.

Throws:

Transformer

FrontendException

transform

public abstract void transform(OperatorPlan matched)
                        throws FrontendException

Transform the tree

Parameters:

matched - the sub-set of the plan that matches the pattern. This subset has the same graph as the pattern, but the operators point to the same objects as the plan to be matched.

Throws:

Transformer

FrontendException

reportChanges

public abstract OperatorPlan reportChanges()

Report what parts of the tree were transformed. This is so that listeners can know which part of the tree to visit and modify schemas, annotations, etc. So any nodes that were removed need will not be in this plan, only nodes that were added or moved.

Returns:

OperatorPlan that describes just the changed nodes.