org.apache.drill.exec.planner.physical.visitor

Class SwapHashJoinVisitor

java.lang.Object

org.apache.drill.exec.planner.physical.visitor.BasePrelVisitor<Prel,Double,RuntimeException>

org.apache.drill.exec.planner.physical.visitor.SwapHashJoinVisitor

All Implemented Interfaces:

PrelVisitor<Prel,Double,RuntimeException>

public class SwapHashJoinVisitor
extends BasePrelVisitor<Prel,Double,RuntimeException>

Visit Prel tree. Find all the HashJoinPrel nodes and set the flag to swap the Left/Right for HashJoinPrel when 1) It's inner join, 2) left rowcount is < (1 + percentage) * right_row_count. The purpose of this visitor is to prevent planner from putting bigger dataset in the RIGHT side, which is not good performance-wise.

See Also:

HashJoinPrel

Field Summary

Fields inherited from interface org.apache.drill.exec.planner.physical.visitor.PrelVisitor

logger

Method Summary

Modifier and Type	Method and Description
static Prel	swapHashJoin(Prel prel, Double marginFactor)
Prel	visitJoin(JoinPrel prel, Double value)
Prel	visitPrel(Prel prel, Double value)

Methods inherited from class org.apache.drill.exec.planner.physical.visitor.BasePrelVisitor

visitExchange, visitLateral, visitLeaf, visitProject, visitScan, visitScan, visitScreen, visitUnnest, visitWriter

Methods inherited from class java.lang.Object

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

Method Detail

swapHashJoin

public static Prel swapHashJoin(Prel prel,
                                Double marginFactor)

visitPrel

public Prel visitPrel(Prel prel,
                      Double value)
               throws RuntimeException

Specified by:

visitPrel in interface PrelVisitor<Prel,Double,RuntimeException>

Overrides:

visitPrel in class BasePrelVisitor<Prel,Double,RuntimeException>

Throws:

RuntimeException

visitJoin

public Prel visitJoin(JoinPrel prel,
                      Double value)
               throws RuntimeException

Specified by:

visitJoin in interface PrelVisitor<Prel,Double,RuntimeException>

Overrides:

visitJoin in class BasePrelVisitor<Prel,Double,RuntimeException>

Throws:

RuntimeException