org.apache.pig.newplan.logical.rules
Class PushDownForEachFlatten

java.lang.Object
  org.apache.pig.newplan.optimizer.Rule
      org.apache.pig.newplan.logical.rules.PushDownForEachFlatten

public class PushDownForEachFlatten
extends Rule

It's generally a good idea to do flattens as late as possible as they tend to generate more rows (and so more I/O). This optimization swaps the order of SORTs, CROSSes and JOINs that come after FOREACH..GENERATE..FLATTENs. FILTERs are re-ordered by the FilterAboveForeach rule so are ignored here.

Field Summary

Fields inherited from class org.apache.pig.newplan.optimizer.Rule

currentPlan, log, name, pattern

Constructor Summary

PushDownForEachFlatten(String name)

Method Summary

protected OperatorPlan	buildPattern() Build the pattern that this rule will look for
Transformer	getNewTransformer() Get the transformer for this rule.

Methods inherited from class org.apache.pig.newplan.optimizer.Rule

getName, getPattern, isMandatory, isSkipListener, match, setSkipListener

Methods inherited from class java.lang.Object

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

Constructor Detail

PushDownForEachFlatten

public PushDownForEachFlatten(String name)

Method Detail

buildPattern

protected OperatorPlan buildPattern()

Description copied from class: Rule

Build the pattern that this rule will look for

Specified by:

buildPattern in class Rule

Returns:

the pattern to look for by this rule

getNewTransformer

public Transformer getNewTransformer()

Description copied from class: Rule

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.

Specified by:

getNewTransformer in class Rule

Returns:

Transformer to use with this rule