org.apache.hadoop.hive.ql.optimizer

Class GroupByOptimizer

java.lang.Object

org.apache.hadoop.hive.ql.optimizer.GroupByOptimizer

All Implemented Interfaces:

Transform

public class GroupByOptimizer
extends Object
implements Transform

This transformation does group by optimization. If the grouping key is a superset of the bucketing and sorting keys of the underlying table in the same order, the group by can be be performed on the map-side completely.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
class	GroupByOptimizer.GroupByOptimizerContext
static class	GroupByOptimizer.GroupByOptimizerSortMatch
class	GroupByOptimizer.SortGroupByProcessor SortGroupByProcessor.
class	GroupByOptimizer.SortGroupBySkewProcessor SortGroupByProcessor.

Constructor Summary

Constructors

Constructor and Description
GroupByOptimizer()

Method Summary

Methods

Modifier and Type	Method and Description
ParseContext	transform(ParseContext pctx) All transformation steps implement this interface.

Methods inherited from class java.lang.Object

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

Constructor Detail

GroupByOptimizer

public GroupByOptimizer()

Method Detail

transform

public ParseContext transform(ParseContext pctx)
                       throws SemanticException

Description copied from interface: Transform

All transformation steps implement this interface.

Specified by:

transform in interface Transform

Parameters:

pctx - input parse context

Returns:

ParseContext

Throws:

SemanticException