Class NullOperator

Represents a part of the algebra that has been determined to not return any results in advance and so can be replaced with this operator which always returns null.

Inheritance

System.Object

NullOperator

Implements

ITerminalOperator

ISparqlAlgebra

IVisitable

IProcessable

Inherited Members

object.Equals(object)

object.Equals(object, object)

object.GetHashCode()

object.GetType()

object.MemberwiseClone()

object.ReferenceEquals(object, object)

Namespace: VDS.RDF.Query.Algebra

Assembly: dotNetRdf.dll

Syntax

public class NullOperator : ITerminalOperator, ISparqlAlgebra, IVisitable, IProcessable

Remarks

Primarily intended for use with Algebra Optimisers which are rewriting the algebra to run against an out of memory dataset (e.g. SQL based) where it may be easily possible to determine if a triple pattern will match in advance of actually returning the matches.

Constructors

NullOperator(IEnumerable<string>)

Creates a new Null Operator.

Declaration

public NullOperator(IEnumerable<string> variables)

Parameters

Type	Name	Description
System.Collections.Generic.IEnumerable<T><string>	variables	Variables in the algebra that this null is replacing.

Remarks

Primarily intended for use with Algebra Optimisers which are rewriting the algebra to run against an out of memory dataset (e.g. SQL based) where it may be easily possible to determine if a triple pattern will match in advance of actually returning the matches.

Properties

FixedVariables

Gets the enumeration of fixed variables in the algebra i.e. variables that are guaranteed to have a bound value.

Declaration

public IEnumerable<string> FixedVariables { get; }

Property Value

Type	Description
System.Collections.Generic.IEnumerable<T><string>

Remarks

Primarily intended for use with Algebra Optimisers which are rewriting the algebra to run against an out of memory dataset (e.g. SQL based) where it may be easily possible to determine if a triple pattern will match in advance of actually returning the matches.

FloatingVariables

Gets the enumeration of floating variables in the algebra i.e. variables that are not guaranteed to have a bound value.

Declaration

public IEnumerable<string> FloatingVariables { get; }

Property Value

Type	Description
System.Collections.Generic.IEnumerable<T><string>

Remarks

Primarily intended for use with Algebra Optimisers which are rewriting the algebra to run against an out of memory dataset (e.g. SQL based) where it may be easily possible to determine if a triple pattern will match in advance of actually returning the matches.

Variables

Gets the variables used in this algebra.

Declaration

public IEnumerable<string> Variables { get; }

Property Value

Type	Description
System.Collections.Generic.IEnumerable<T><string>

Remarks

Primarily intended for use with Algebra Optimisers which are rewriting the algebra to run against an out of memory dataset (e.g. SQL based) where it may be easily possible to determine if a triple pattern will match in advance of actually returning the matches.

Methods

Accept<T>(ISparqlAlgebraVisitor<T>)

Declaration

public T Accept<T>(ISparqlAlgebraVisitor<T> visitor)

Parameters

Type	Name	Description
ISparqlAlgebraVisitor<T>	visitor

Returns

Type	Description
T

Type Parameters

Name	Description
T

Remarks

Primarily intended for use with Algebra Optimisers which are rewriting the algebra to run against an out of memory dataset (e.g. SQL based) where it may be easily possible to determine if a triple pattern will match in advance of actually returning the matches.

Accept<TResult, TContext>(ISparqlQueryAlgebraProcessor<TResult, TContext>, TContext)

Declaration

public TResult Accept<TResult, TContext>(ISparqlQueryAlgebraProcessor<TResult, TContext> processor, TContext context)

Parameters

Type	Name	Description
ISparqlQueryAlgebraProcessor<TResult, TContext>	processor
TContext	context

Returns

Type	Description
TResult

Type Parameters

Name	Description
TResult
TContext

Remarks

Primarily intended for use with Algebra Optimisers which are rewriting the algebra to run against an out of memory dataset (e.g. SQL based) where it may be easily possible to determine if a triple pattern will match in advance of actually returning the matches.

ToGraphPattern()

Throws an error since a null operator cannot be transformed back into a query.

Declaration

public GraphPattern ToGraphPattern()

Returns

Type	Description
GraphPattern

Remarks

Primarily intended for use with Algebra Optimisers which are rewriting the algebra to run against an out of memory dataset (e.g. SQL based) where it may be easily possible to determine if a triple pattern will match in advance of actually returning the matches.

ToQuery()

Throws an error since a null operator cannot be transformed back into a query.

Declaration

public SparqlQuery ToQuery()

Returns

Type	Description
SparqlQuery

Remarks

Primarily intended for use with Algebra Optimisers which are rewriting the algebra to run against an out of memory dataset (e.g. SQL based) where it may be easily possible to determine if a triple pattern will match in advance of actually returning the matches.

ToString()

Gets the string representation of the algebra.

Declaration

public override string ToString()

Returns

Type	Description
string

Overrides

object.ToString()

Remarks

Primarily intended for use with Algebra Optimisers which are rewriting the algebra to run against an out of memory dataset (e.g. SQL based) where it may be easily possible to determine if a triple pattern will match in advance of actually returning the matches.

Implements

ITerminalOperator

ISparqlAlgebra

IVisitable

IProcessable

Extension Methods

Extensions.ToSafeString(object)

Extensions.AsEnumerable<T>(T)