org.apache.pig.newplan.optimizer
Class Rule

java.lang.Object
  org.apache.pig.newplan.optimizer.Rule

Direct Known Subclasses:

DuplicateForEachColumnRewrite, FilterAboveForeach, GroupByConstParallelSetter, ImplicitSplitInserter, LimitOptimizer, LogicalExpressionSimplifier, MergeFilter, MergeForEach, PartitionFilterOptimizer, PushDownForEachFlatten, PushUpFilter, SplitFilter, TypeCastInserter, WholePlanRule

public abstract class Rule
extends Object

Rules describe a pattern of operators. They also reference a Transformer. If the pattern of operators is found one or more times in the provided plan, then the optimizer will use the associated Transformer to transform the plan. Note: the pattern matching logic implemented here has a limitation that it assumes that all the leaves in the pattern are siblings. See more detailed description here - https://issues.apache.org/jira/browse/PIG-1742 If new rules use patterns that don't work with this limitation, the pattern match logic will need to be updated.

Field Summary

protected OperatorPlan	currentPlan
protected static org.apache.commons.logging.Log	log
protected String	name
protected OperatorPlan	pattern

Constructor Summary

Rule(String n, boolean mandatory)
Create this rule by using the default pattern that this rule provided

Rule(String n, OperatorPlan p)

Method Summary

protected abstract OperatorPlan	buildPattern() Build the pattern that this rule will look for
String	getName()
abstract Transformer	getNewTransformer() Get the transformer for this rule.
OperatorPlan	getPattern() Return the pattern to be matched for this rule
boolean	isMandatory()
protected boolean	isSkipListener()
List<OperatorPlan>	match(OperatorPlan plan) Search for all the sub-plans that matches the pattern defined by this rule.
protected void	setSkipListener(boolean skip)

Methods inherited from class java.lang.Object

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

Field Detail

name

protected String name

pattern

protected OperatorPlan pattern

currentPlan

protected transient OperatorPlan currentPlan

log

protected static final org.apache.commons.logging.Log log

Constructor Detail

Rule

public Rule(String n,
            boolean mandatory)

Create this rule by using the default pattern that this rule provided

Parameters:

n - Name of this rule

mandatory - if it is set to false, this rule can be disabled by user

Rule

public Rule(String n,
            OperatorPlan p)

Parameters:

n - Name of this rule

p - Pattern to look for.

Method Detail

buildPattern

protected abstract OperatorPlan buildPattern()

Build the pattern that this rule will look for

Returns:

the pattern to look for by this rule

getNewTransformer

public abstract Transformer getNewTransformer()

Get the transformer for this rule. Abstract because the rule may want to choose how to instantiate the transformer. This should never return a cached transformer, it should always return a fresh one with no state.

Returns:

Transformer to use with this rule

getPattern

public OperatorPlan getPattern()

Return the pattern to be matched for this rule

Returns:

the pattern to be matched for this rule

isSkipListener

protected boolean isSkipListener()

setSkipListener

protected void setSkipListener(boolean skip)

match

public List<OperatorPlan> match(OperatorPlan plan)
                         throws FrontendException

Search for all the sub-plans that matches the pattern defined by this rule. See class description above for limitations on the patterns supported.

Parameters:

plan - the OperatorPlan to look for matches to the pattern

Returns:

A list of all matched sub-plans. The returned plans are partial views of the original OperatorPlan. Each is a sub-set of the original plan and represents the same topology as the pattern, but operators in the returned plan are the same objects as the original plan. Therefore, a call getPlan() from any node in the return plan would return the original plan.

Throws:

FrontendException

getName

public String getName()

isMandatory

public boolean isMandatory()