io.prestosql.sql.planner.iterative.rule

Class AddExchangesBelowPartialAggregationOverGroupIdRuleSet

java.lang.Object

io.prestosql.sql.planner.iterative.rule.AddExchangesBelowPartialAggregationOverGroupIdRuleSet

public class AddExchangesBelowPartialAggregationOverGroupIdRuleSet
extends Object

Transforms

   - Exchange
     - [ Projection ]
       - Partial Aggregation
         - GroupId
 

to

   - Exchange
     - [ Projection ]
       - Partial Aggregation
         - GroupId
           - LocalExchange
             - RemoteExchange
 

Rationale: GroupId increases number of rows (number of times equal to number of grouping sets) and then partial aggregation reduces number of rows. However, under certain conditions, exchanging the rows before GroupId (before multiplication) makes partial aggregation more effective, resulting in less data being exchanged afterwards.

Constructor Summary

Constructors

Constructor and Description
AddExchangesBelowPartialAggregationOverGroupIdRuleSet(Metadata metadata, TypeAnalyzer typeAnalyzer, TaskCountEstimator taskCountEstimator, TaskManagerConfig taskManagerConfig)

Method Summary

Modifier and Type	Method and Description
Set<Rule<?>>	rules()

Methods inherited from class java.lang.Object

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

Constructor Detail

AddExchangesBelowPartialAggregationOverGroupIdRuleSet

public AddExchangesBelowPartialAggregationOverGroupIdRuleSet(Metadata metadata,
                                                             TypeAnalyzer typeAnalyzer,
                                                             TaskCountEstimator taskCountEstimator,
                                                             TaskManagerConfig taskManagerConfig)

Method Detail

rules

public Set<Rule<?>> rules()