Class CardinalityBasedJoinOrderingWithRequests

java.lang.Object

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

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

All Implemented Interfaces:

HeuristicForLogicalOptimization

public class CardinalityBasedJoinOrderingWithRequests
extends CardinalityBasedJoinOrderingBase

This class is an implementation of CardinalityBasedJoinOrderingBase that uses cardinality requests. That is, this class implements the function

invalid reference

CardinalityBasedJoinOrderingBase#estimateCardinalities(LogicalPlan[] plans)

by, first, issuing cardinality requests for every request operator within each of the given plans; then, for each given plan, the cardinalities for obtained for the corresponding request operators are aggregated. Currently, this aggregation is just a sum, ignoring whether there are filters or l2g operators in the plans. The implementation of the second of the abstract functions of the base class,

invalid reference

CardinalityBasedJoinOrderingBase#estimateJoinCardinality(List<AnnotatedLogicalPlan> selectedPlans, int joinCardOfSelectedPlans, AnnotatedLogicalPlan nextCandidate)

, simply returns the cardinality estimate of the given next candidate subplan. Hence, when deciding which next candidate subplan to add to the join order, this implementation greedily picks the candidate with the lowest cardinality (without considering join cardinalities or anything even more sophisticated). Subclasses may change this behavior. The current implementation of this class assumes that all logical plans under joins (i.e., all plans for which the cardinality needs to be estimated) are either: i) a single request, ii) a filter over a request, iii) an l2g over a request, iv) a filter over an l2g over a request, v) an l2g over a filter over a request, vi) a union over any of the aforementioned options, or vii) an l2g over a union over any of the aforementioned (non-union) options.

Field Summary

Fields

Modifier and Type	Field	Description
protected final QueryProcContext	ctxt

Fields inherited from class se.liu.ida.hefquin.engine.queryproc.impl.loptimizer.heuristics.CardinalityBasedJoinOrderingBase

cardEst

Constructor Summary

Constructors

Constructor	Description
CardinalityBasedJoinOrderingWithRequests(QueryProcContext ctxt)

Method Summary

Modifier and Type	Method	Description
protected int	estimateJoinCardinality(List<LogicalPlan> selectedPlans, int joinCardOfSelectedPlans, LogicalPlan nextCandidate)	Implementations of this function estimate the cardinality of the join between the result of joining the given selected plans and the result of the given next candidate.

Methods inherited from class se.liu.ida.hefquin.engine.queryproc.impl.loptimizer.heuristics.CardinalityBasedJoinOrderingBase

_apply, apply, containsJoinOp, determineIdxOfSmallestCardinality, determineNextPlan, reorder

Methods inherited from class java.lang.Object

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

Field Details

ctxt

protected final QueryProcContext ctxt

Constructor Details

CardinalityBasedJoinOrderingWithRequests

public CardinalityBasedJoinOrderingWithRequests(QueryProcContext ctxt)

Method Details

estimateJoinCardinality

protected int estimateJoinCardinality(List<LogicalPlan> selectedPlans,
 int joinCardOfSelectedPlans,
 LogicalPlan nextCandidate)

Description copied from class: CardinalityBasedJoinOrderingBase

Implementations of this function estimate the cardinality of the join between the result of joining the given selected plans and the result of the given next candidate. Implementations that require the individual cardinality estimates for each of the plans can get these estimates by accessing QueryPlan.getQueryPlanningInfo(). The estimated join cardinality of joining the given selected plans is also passed to this function, in case it is needed by some implementation.

Specified by:

estimateJoinCardinality in class CardinalityBasedJoinOrderingBase