Class VariableSubstitutionTransformer

An optimiser for walking algebra and expression trees and replacing a Variable with another Variable or a Constant.

Inheritance
System.Object
PrimaryExpressionSubstituter
VariableSubstitutionTransformer
Implements
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 class VariableSubstitutionTransformer : PrimaryExpressionSubstituter, IExpressionTransformer, IAlgebraOptimiser

Constructors

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VariableSubstitutionTransformer(string, string)

Create a transform that replaces one variable with another.

Declaration
public VariableSubstitutionTransformer(string findVar, string replaceVar)
Parameters
Type Name Description
string findVar

Find Variable.
string replaceVar

Replace Variable.
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VariableSubstitutionTransformer(string, INode)

Create a transform that replaces a variable with a constant.

Declaration
public VariableSubstitutionTransformer(string findVar, INode replaceTerm)
Parameters
Type Name Description
string findVar

Find Variable.
INode replaceTerm

Replace Constant.

Properties

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CanReplaceObjects

Gets/Sets whethe the Transformer is allowed to replace objects.

Declaration
public bool CanReplaceObjects { get; set; }
Property Value
Type Description
System.Boolean
Remarks

The transformer will intelligently select this depending on whether it is replacing with a constant (defaults to true) or a variable (defaults to false), when replacing a variable the behaviour changes automatically. If you set it explicitly the transformer will respect your setting regardless.

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UnsafeOptimisation

Determines whether an Optimiser will perform algebra optimizations that are potentially unsafe at execution time.

Declaration
public bool UnsafeOptimisation { get; set; }
Property Value
Type Description
System.Boolean

Methods

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IsApplicable(SparqlQuery)

Returns false because this optimiser is never globally applicable.

Declaration
public bool IsApplicable(SparqlQuery q)
Parameters
Type Name Description
SparqlQuery q

Query.
Returns
Type Description
System.Boolean
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IsApplicable(SparqlUpdateCommandSet)

Returns false because this optimiser is never globally applicable.

Declaration
public bool IsApplicable(SparqlUpdateCommandSet cmds)
Parameters
Type Name Description
SparqlUpdateCommandSet cmds

Update Commands.
Returns
Type Description
System.Boolean
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Optimise(ISparqlAlgebra)

Attempts to do variable substitution within the given algebra.

Declaration
public ISparqlAlgebra Optimise(ISparqlAlgebra algebra)
Parameters
Type Name Description
ISparqlAlgebra algebra

Algebra.
Returns
Type Description
ISparqlAlgebra
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SubstitutePrimaryExpression(ISparqlExpression)

Tries to substitute variables within primary expressions.

Declaration
protected override ISparqlExpression SubstitutePrimaryExpression(ISparqlExpression expr)
Parameters
Type Name Description
ISparqlExpression expr

Expression.
Returns
Type Description
ISparqlExpression
Overrides

Implements

Extension Methods