org.apache.tajo.plan.joinorder

Class GreedyHeuristicJoinOrderAlgorithm

java.lang.Object

org.apache.tajo.plan.joinorder.GreedyHeuristicJoinOrderAlgorithm

All Implemented Interfaces:

JoinOrderAlgorithm

public class GreedyHeuristicJoinOrderAlgorithm
extends Object
implements JoinOrderAlgorithm

This is a greedy heuristic algorithm to find a bushy join tree. This algorithm finds the best join order with join conditions and pushed-down join conditions to all join operators.

Field Summary

Fields

Modifier and Type	Field and Description
static double	DEFAULT_SELECTION_FACTOR

Constructor Summary

Constructors

Constructor and Description
GreedyHeuristicJoinOrderAlgorithm()

Method Summary

Methods

Modifier and Type	Method and Description
FoundJoinOrder	findBestOrder(LogicalPlan plan, LogicalPlan.QueryBlock block, JoinGraph joinGraph, Set<String> relationsWithoutQual)
static double	getCost(JoinEdge joinEdge) Getting a cost of one join
static double	getCost(LogicalNode node)

Methods inherited from class java.lang.Object

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

Field Detail

DEFAULT_SELECTION_FACTOR

public static double DEFAULT_SELECTION_FACTOR

Constructor Detail

GreedyHeuristicJoinOrderAlgorithm

public GreedyHeuristicJoinOrderAlgorithm()

Method Detail

findBestOrder

public FoundJoinOrder findBestOrder(LogicalPlan plan,
                           LogicalPlan.QueryBlock block,
                           JoinGraph joinGraph,
                           Set<String> relationsWithoutQual)
                             throws PlanningException

Specified by:

findBestOrder in interface JoinOrderAlgorithm

joinGraph - A join graph represents join conditions and their connections among relations. Given a graph, each vertex represents a relation, and each edge contains a join condition. A join graph does not contain relations that do not have any corresponding join condition.

relationsWithoutQual - The names of relations that do not have any corresponding join condition.

Returns:

Throws:

PlanningException

getCost

public static double getCost(JoinEdge joinEdge)

Getting a cost of one join

Parameters:

joinEdge -

Returns:

getCost

public static double getCost(LogicalNode node)