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

java.lang.Object
  extended by org.apache.pig.newplan.optimizer.Rule
      extended by org.apache.pig.newplan.logical.rules.GroupByConstParallelSetter

public class GroupByConstParallelSetter
extends Rule

Rule: If a LOCogroup is 'group all', set the parallelism to 1, or in general - if the group-by expression is just a constant then set parallelism to 1 LogicalExpressionSimplifier could be used to convert an expression with constants into a single ConstantExpression


Nested Class Summary
 class GroupByConstParallelSetter.GroupAllParallelSetterTransformer
           
 
Field Summary
 
Fields inherited from class org.apache.pig.newplan.optimizer.Rule
currentPlan, name, pattern
 
Constructor Summary
GroupByConstParallelSetter(String n)
           
 
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

GroupByConstParallelSetter

public GroupByConstParallelSetter(String n)
Method Detail

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

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


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