Class LeviathanOptimiser

Static Helper class which provides global registry of Algebra Optimisers and the global Query Optimiser.

Inheritance

object

LeviathanOptimiser

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 static class LeviathanOptimiser

Fields

OptimiserStatsNamespace

Namespace URI for the Optimiser Statistics vocabulary.

Declaration

public const string OptimiserStatsNamespace = "http://www.dotnetrdf.org/optimiserStats#"

Field Value

Type	Description
string

Properties

AlgebraOptimisers

Gets the global Algebra Optimisers that are in use.

Declaration

public static IEnumerable<IAlgebraOptimiser> AlgebraOptimisers { get; }

Property Value

Type	Description
IEnumerable<IAlgebraOptimiser>

Remarks

Unlike Query Optimisation multiple Algebra Optimisations may apply. Algebra optimisers may also be specified and apply locally by the use of the relevant properties on the SparqlQueryParser and SparqlQuery classes. Those specified on a parser will automatically be passed through to all queries parsed by the parser. Locally specified optimisers apply prior to globally specified ones.

QueryOptimiser

Gets/Sets the global Query Optimiser that is used by default.

Declaration

public static IQueryOptimiser QueryOptimiser { get; set; }

Property Value

Type	Description
IQueryOptimiser

Remarks

Note: May be overridden by the Optimiser setting on a SparqlQueryParser.

Unlike previous releases a Query may be reoptimised using a different optimiser if desired by calling the Optimise() method again and providing a different Optimiser. This may not always fully reoptimise the query since the first optimisation will have caused any Filters and Assignments to be placed in the Triple Pattern.

Warning: Setting this to null has no effect, to disable automatic optimisation use the QueryOptimisation property for query parsing or QueryOptimisation property for SPARQL update parsing. Even with this option disabled a Query can still be optimised manually by calling its Optimise() method.

Methods

AddOptimiser(IAlgebraOptimiser)

Adds a new Algebra Optimiser.

Declaration

public static void AddOptimiser(IAlgebraOptimiser optimiser)

Parameters

Type	Name	Description
IAlgebraOptimiser	optimiser	Optimiser.

RemoveOptimiser(IAlgebraOptimiser)

Removes an Algebra Optimiser.

Declaration

public static void RemoveOptimiser(IAlgebraOptimiser optimiser)

Parameters

Type	Name	Description
IAlgebraOptimiser	optimiser

ResetOptimisers()

Resets Optimisers to default settings.

Declaration

public static void ResetOptimisers()