Class MergeRequests

java.lang.Object

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

All Implemented Interfaces:

HeuristicForLogicalOptimization

public class MergeRequests
extends Object
implements HeuristicForLogicalOptimization

Merges subplans that consists of multiple requests to the same federation member if such a merge is possible. In particular, a join over two requests is merged into a single request operator if i) the two requests are triple pattern requests (which can be merged into a BGP request and the federation member supports BGP requests, or ii) one of the two requests is a BGP request and the other one also a BGP request or a triple pattern request. Another possibility for merging is a join over two arbitrary SPARQL pattern requests for a SPARQL endpoint. For SPARQL endpoints, this heuristic even tries to push other operators into requests (filters, unions, optional). The aforementioned join-related merge is performed not only for binary join operators but also for gpAdd operators over request operators, as well as for pairs of requests under a multi-join. In the latter case, the multi-join operator is replaced by the merged request operator only if there are no other subplans under that multi-join operator. The merging is applied recursively in a bottom-up fashion, which means that, after performing one merge step, another one may become available and will be done.

Constructor Summary

Constructors

Constructor	Description
MergeRequests()

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	createPlanWithSingleRequestOp(SPARQLGraphPattern p, FederationMember fm)
protected SPARQLGraphPattern	mergePatternWithOptPatterns(SPARQLGraphPattern pattern, SPARQLGraphPattern... optPatterns)
protected LogicalPlan	mergeSPARQLRequestsViaJoin(FederationMember fm, List<LogicalPlan> reqPlans)	Assumes that the given list contains at least two plans and that all plans in the list consist only of a request operator.
protected SPARQLGraphPattern	mergeSPARQLRequestsViaUnion(List<LogicalPlan> reqPlans)	Assumes that the given list contains at least two plans and that all plans in the list consist only of a request operator.
protected void	separateSubPlansOfMultiwayOps(List<LogicalPlan> subPlans, Map<FederationMember,List<LogicalPlan>> reqOnlyPlansPerFedMember, List<LogicalPlan> nonReqSubPlans)

Methods inherited from class java.lang.Object

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

Constructor Details

MergeRequests

public MergeRequests()

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

mergeSPARQLRequestsViaUnion

protected SPARQLGraphPattern mergeSPARQLRequestsViaUnion(List<LogicalPlan> reqPlans)

Assumes that the given list contains at least two plans and that all plans in the list consist only of a request operator.

mergeSPARQLRequestsViaJoin

protected LogicalPlan mergeSPARQLRequestsViaJoin(FederationMember fm,
 List<LogicalPlan> reqPlans)

Assumes that the given list contains at least two plans and that all plans in the list consist only of a request operator. Returns null if the given federation member does not support the merged pattern.

mergePatternWithOptPatterns

protected SPARQLGraphPattern mergePatternWithOptPatterns(SPARQLGraphPattern pattern,
 SPARQLGraphPattern... optPatterns)

createPlanWithSingleRequestOp

protected LogicalPlan createPlanWithSingleRequestOp(SPARQLGraphPattern p,
 FederationMember fm)

separateSubPlansOfMultiwayOps

protected void separateSubPlansOfMultiwayOps(List<LogicalPlan> subPlans,
 Map<FederationMember,List<LogicalPlan>> reqOnlyPlansPerFedMember,
 List<LogicalPlan> nonReqSubPlans)