Package se.liu.ida.hefquin.engine.queryproc.impl.loptimizer.heuristics

Class GreedyBasedReordering

java.lang.Object

se.liu.ida.hefquin.engine.queryproc.impl.loptimizer.heuristics.GreedyBasedReordering

All Implemented Interfaces:

HeuristicForLogicalOptimization

public class GreedyBasedReordering
extends Object
implements HeuristicForLogicalOptimization

Implement a greedy algorithm to determine the join order of sub-plans. For a given logical plan, when a sub-plan with LogicalOpMultiwayJoin or LogicalOpJoin as the root operator is found, the order of sub-plans is determined by the unrestrictiveness score (so-called cost): starting with the sub-plan with the smallest cost and continuing with the next sub-plan with the smallest cost. Any of the defined formulas can be used for calculating the cost value to find the optimal order. One example of such formulas is JoinAwareWeightedUnboundVariableCount.

Field Summary

Fields

Modifier and Type	Field	Description
protected final FormulaForComputingSelectivity	formula

Constructor Summary

Constructors

Constructor	Description
GreedyBasedReordering(FormulaForComputingSelectivity formula)

Method Summary

Modifier and Type	Method	Description
LogicalPlan	apply(LogicalPlan inputPlan)	Applies this heuristics to the given plan and returns the resulting, potentially rewritten plan.
protected LogicalPlan	constructBinaryPlan(List<QueryAnalyzer> selectedSubPlans)
protected QueryAnalyzer	findNextPlan(List<QueryAnalyzer> selectedSubPlans, List<QueryAnalyzer> candidatePlans)
protected LogicalPlan	reorderSubPlans(LogicalPlan inputPlan)

Methods inherited from class java.lang.Object

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

Field Details

formula

protected final FormulaForComputingSelectivity formula

Constructor Details

GreedyBasedReordering

public GreedyBasedReordering(FormulaForComputingSelectivity formula)

Method Details

apply

public LogicalPlan apply(LogicalPlan inputPlan)

Description copied from interface: HeuristicForLogicalOptimization

Applies this heuristics to the given plan and returns the resulting, potentially rewritten plan.

Specified by:

apply in interface HeuristicForLogicalOptimization

reorderSubPlans

protected LogicalPlan reorderSubPlans(LogicalPlan inputPlan)

findNextPlan

protected QueryAnalyzer findNextPlan(List<QueryAnalyzer> selectedSubPlans,
 List<QueryAnalyzer> candidatePlans)

constructBinaryPlan

protected LogicalPlan constructBinaryPlan(List<QueryAnalyzer> selectedSubPlans)