org.apache.hadoop.hive.ql.optimizer.stats.annotation
Class StatsRulesProcFactory.FilterStatsRule

java.lang.Object
  extended by org.apache.hadoop.hive.ql.optimizer.stats.annotation.StatsRulesProcFactory.DefaultStatsRule
      extended by org.apache.hadoop.hive.ql.optimizer.stats.annotation.StatsRulesProcFactory.FilterStatsRule
All Implemented Interfaces:
NodeProcessor
Enclosing class:
StatsRulesProcFactory

public static class StatsRulesProcFactory.FilterStatsRule
extends StatsRulesProcFactory.DefaultStatsRule
implements NodeProcessor

FILTER operator does not change the average row size but it does change the number of rows emitted. The reduction in the number of rows emitted is dependent on the filter expression.

Worst case: If no column statistics are available, then evaluation of predicate expression will assume worst case (i.e; half the input rows) for each of predicate expression.

For more information, refer 'Estimating The Cost Of Operations' chapter in "Database Systems: The Complete Book" by Garcia-Molina et. al.


Constructor Summary
StatsRulesProcFactory.FilterStatsRule()
           
 
Method Summary
 Object process(Node nd, Stack<Node> stack, NodeProcessorCtx procCtx, Object... nodeOutputs)
          Generic process for all ops that don't have specific implementations.
 
Methods inherited from class java.lang.Object
equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

StatsRulesProcFactory.FilterStatsRule

public StatsRulesProcFactory.FilterStatsRule()
Method Detail

process

public Object process(Node nd,
                      Stack<Node> stack,
                      NodeProcessorCtx procCtx,
                      Object... nodeOutputs)
               throws SemanticException
Description copied from interface: NodeProcessor
Generic process for all ops that don't have specific implementations.

Specified by:
process in interface NodeProcessor
Overrides:
process in class StatsRulesProcFactory.DefaultStatsRule
Parameters:
nd - operator to process
procCtx - operator processor context
nodeOutputs - A variable argument list of outputs from other nodes in the walk
Returns:
Object to be returned by the process call
Throws:
SemanticException


Copyright © 2014 The Apache Software Foundation. All rights reserved.