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

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

public class ColumnMapKeyPrune
extends WholePlanRule

This Rule prunes columns and map keys and set to loader. This rule depends on MapKeysPruneHelper to calculate what keys are required for a loader, and ColumnPruneHelper to calculate the required columns for a loader. Then it combines the map keys and columns info to set into the loader.

Nested Class Summary

class

ColumnMapKeyPrune.ColumnMapKeyPruneTransformer

Field Summary

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

currentPlan, log, name, pattern

Constructor Summary

ColumnMapKeyPrune(String n)

Method Summary

Transformer

getNewTransformer() Get the transformer for this rule.

Methods inherited from class org.apache.pig.newplan.logical.rules.WholePlanRule

buildPattern, match

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

getName, getPattern, isMandatory, isSkipListener, setSkipListener

Methods inherited from class java.lang.Object

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

Constructor Detail

ColumnMapKeyPrune

public ColumnMapKeyPrune(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