Class SpatialStrategy

The SpatialStrategy encapsulates an approach to indexing and searching based on shapes.

Different implementations will support different features. A strategy should document these common elements:

Can it index more than one shape per field?
What types of shapes can be indexed?
What types of query shapes can be used?
What types of query operations are supported? This might vary per shape.
Does it use the FieldCache, or some other type of cache? When?

If a strategy only supports certain shapes at index or query time, then in general it will throw an exception if given an incompatible one. It will not be coerced into compatibility.

Note that a SpatialStrategy is not involved with the Lucene stored field values of shapes, which is immaterial to indexing and search.

Thread-safe.

This is a Lucene.NET EXPERIMENTAL API, use at your own risk

Inheritance

System.Object

SpatialStrategy

PrefixTreeStrategy

SerializedDVStrategy

PointVectorStrategy

Inherited Members

System.Object.Equals(System.Object)

System.Object.Equals(System.Object, System.Object)

System.Object.GetHashCode()

System.Object.GetType()

System.Object.MemberwiseClone()

System.Object.ReferenceEquals(System.Object, System.Object)

Namespace: Lucene.Net.Spatial

Assembly: Lucene.Net.Spatial.dll

Syntax

public abstract class SpatialStrategy

Constructors

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SpatialStrategy(SpatialContext, String)

Constructs the spatial strategy with its mandatory arguments.

Declaration

protected SpatialStrategy(SpatialContext ctx, string fieldName)

Parameters

Type	Name	Description
Spatial4n.Core.Context.SpatialContext	ctx
System.String	fieldName

Fields

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m_ctx

Declaration

protected readonly SpatialContext m_ctx

Field Value

Type	Description
Spatial4n.Core.Context.SpatialContext

Properties

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FieldName

The name of the field or the prefix of them if there are multiple fields needed internally.

Declaration

public virtual string FieldName { get; }

Property Value

Type	Description
System.String	Not null.

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SpatialContext

Declaration

public virtual SpatialContext SpatialContext { get; }

Property Value

Type	Description
Spatial4n.Core.Context.SpatialContext

Methods

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CreateIndexableFields(IShape)

Returns the IndexableField(s) from the shape that are to be added to the Document. These fields are expected to be marked as indexed and not stored.

Note: If you want to store the shape as a string for retrieval in search results, you could add it like this:

    document.Add(new StoredField(fieldName, ctx.ToString(shape)));

The particular string representation used doesn't matter to the Strategy since it doesn't use it.

Declaration

public abstract Field[] CreateIndexableFields(IShape shape)

Parameters

Type	Name	Description
Spatial4n.Core.Shapes.IShape	shape

Returns

Type	Description
Field[]	Not null nor will it have null elements.

Exceptions

Type	Condition
System.NotSupportedException	if given a shape incompatible with the strategy

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MakeDistanceValueSource(IPoint)

See MakeDistanceValueSource(IPoint, Double) called with a multiplier of 1.0 (i.e. units of degrees).

Declaration

public virtual ValueSource MakeDistanceValueSource(IPoint queryPoint)

Parameters

Type	Name	Description
Spatial4n.Core.Shapes.IPoint	queryPoint

Returns

Type	Description
Lucene.Net.Queries.Function.ValueSource

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MakeDistanceValueSource(IPoint, Double)

Make a ValueSource returning the distance between the center of the indexed shape and queryPoint. If there are multiple indexed shapes then the closest one is chosen. The result is multiplied by multiplier, which conveniently is used to get the desired units.

Declaration

public abstract ValueSource MakeDistanceValueSource(IPoint queryPoint, double multiplier)

Parameters

Type	Name	Description
Spatial4n.Core.Shapes.IPoint	queryPoint
System.Double	multiplier

Returns

Type	Description
Lucene.Net.Queries.Function.ValueSource

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MakeFilter(SpatialArgs)

Make a Filter based principally on SpatialOperation and Spatial4n.Core.Shapes.IShape from the supplied args.

If a subclasses implements MakeQuery(SpatialArgs) then this method could be simply:

return new QueryWrapperFilter(MakeQuery(args).Query);

Declaration

public abstract Filter MakeFilter(SpatialArgs args)

Parameters

Type	Name	Description
SpatialArgs	args

Returns

Type	Description
Lucene.Net.Search.Filter

Exceptions

Type	Condition
System.NotSupportedException	If the strategy does not support the shape in `args`.
UnsupportedSpatialOperation	If the strategy does not support the SpatialOperation in `args`.

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MakeQuery(SpatialArgs)

Make a Query based principally on SpatialOperation and Spatial4n.Core.Shapes.IShape from the supplied args. The default implementation is

return new ConstantScoreQuery(MakeFilter(args));

Declaration

public virtual ConstantScoreQuery MakeQuery(SpatialArgs args)

Parameters

Type	Name	Description
SpatialArgs	args

Returns

Type	Description
Lucene.Net.Search.ConstantScoreQuery

Exceptions

Type	Condition
System.NotSupportedException	If the strategy does not support the shape in `args`.
UnsupportedSpatialOperation	If the strategy does not support the SpatialOperation in `args`.

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MakeRecipDistanceValueSource(IShape)

Returns a ValueSource with values ranging from 1 to 0, depending inversely on the distance from MakeDistanceValueSource(IPoint). The formula is c / (d + c) where 'd' is the distance and 'c' is one tenth the distance to the farthest edge from the center. Thus the scores will be 1 for indexed points at the center of the query shape and as low as ~0.1 at its furthest edges.

Declaration

public ValueSource MakeRecipDistanceValueSource(IShape queryShape)

Parameters

Type	Name	Description
Spatial4n.Core.Shapes.IShape	queryShape

Returns

Type	Description
Lucene.Net.Queries.Function.ValueSource

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ToString()

Declaration

public override string ToString()

Returns

Type	Description
System.String

Overrides

System.Object.ToString()