Class BaseQueryOptimiser

A basic abstract implementation of a Query Optimiser.

Inheritance

object

BaseQueryOptimiser

DefaultOptimiser

NoReorderOptimiser

WeightedOptimiser

Implements

IQueryOptimiser

Inherited Members

object.Equals(object)

object.Equals(object, object)

object.GetHashCode()

object.GetType()

object.MemberwiseClone()

object.ReferenceEquals(object, object)

object.ToString()

Namespace: VDS.RDF.Query.Optimisation

Assembly: dotNetRdf.dll

Syntax

public abstract class BaseQueryOptimiser : IQueryOptimiser

Remarks

Derived implementations may use override the virtual properties to control what forms of optimisation are used. Derived implementations must override the GetRankingComparer() method, optimisers which do not wish to change the order of Triple Patterns should return the NoReorderCompaper in their implementation as a basic sort of Triple Patterns is done even if ShouldReorder is overridden to return false.

Properties

ShouldPlaceAssignments

Controls whether the Optimiser will place Assignments.

Declaration

protected virtual bool ShouldPlaceAssignments { get; }

Property Value

Type	Description
bool

Remarks

It is recommended that derived classes do not change this setting as this may hurt performance. If you want to control the optimisation process in detail we suggest you implement IQueryOptimiser directly in your own class and not derive from this implementation.

ShouldPlaceFilters

Controls whether the Optimiser will place Filters.

Declaration

protected virtual bool ShouldPlaceFilters { get; }

Property Value

Type	Description
bool

Remarks

It is recommended that derived classes do not change this setting as this may hurt performance. If you want to control the optimisation process in detail we suggest you implement IQueryOptimiser directly in your own class and not derive from this implementation.

ShouldReorder

Controls whether the Optimiser will attempt to reorder Triple Patterns.

Declaration

protected virtual bool ShouldReorder { get; }

Property Value

Type	Description
bool

Remarks

It is recommended that derived classes do not change this setting as this may hurt performance. If you want to control the optimisation process in detail we suggest you implement IQueryOptimiser directly in your own class and not derive from this implementation.

ShouldSplitFilters

Controls whether the Optimiser will split Filters.

Declaration

protected virtual bool ShouldSplitFilters { get; }

Property Value

Type	Description
bool

Remarks

If a Filter contains an and expression it may be split into its constituent parts and applied separately. This option only applies if filter placement also applies.

Defaults to false since it is unclear if this actually benefits performance.

Methods

GetRankingComparer()

Gets a comparer on Triple Patterns that is used to rank Triple Patterns.

Declaration

protected abstract IComparer<ITriplePattern> GetRankingComparer()

Returns

Type	Description
IComparer<ITriplePattern>

Remarks

By overriding this in derived classes you can change how the Optimiser weights different patterns and thus the resultant ordering of Triple Patterns.

Optimise(GraphPattern, IEnumerable<string>)

Causes the Graph Pattern to be optimised if it isn't already.

Declaration

public void Optimise(GraphPattern gp, IEnumerable<string> variables)

Parameters

Type	Name	Description
GraphPattern	gp	Graph Pattern.
IEnumerable<string>	variables	Variables that have occurred prior to this Pattern.

Implements

IQueryOptimiser

Extension Methods

Extensions.ToSafeString(object)

Extensions.AsEnumerable<T>(T)