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
Namespace: Lucene.Net.Spatial
Assembly: Lucene.Net.Spatial.dll
Syntax
public abstract class SpatialStrategy : object

Constructors

| Improve this Doc View Source

SpatialStrategy(SpatialContext, String)

Constructs the spatial strategy with its mandatory arguments.

Declaration
protected SpatialStrategy(SpatialContext ctx, string fieldName)
Parameters
Type Name Description
SpatialContext ctx
System.String fieldName

Fields

| Improve this Doc View Source

m_ctx

Declaration
protected readonly SpatialContext m_ctx
Field Value
Type Description
SpatialContext

Properties

| Improve this Doc View Source

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.
| Improve this Doc View Source

SpatialContext

Declaration
public virtual SpatialContext SpatialContext { get; }
Property Value
Type Description
SpatialContext

Methods

| Improve this Doc View Source

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
IShape shape
Returns
Type Description
Field[]

Not null nor will it have null elements.
| Improve this Doc View Source

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
IPoint queryPoint
Returns
Type Description
ValueSource
| Improve this Doc View Source

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
IPoint queryPoint
System.Double multiplier
Returns
Type Description
ValueSource
| Improve this Doc View Source

MakeFilter(SpatialArgs)

Make a Filter based principally on SpatialOperation and 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
Filter
Exceptions
Type Condition
UnsupportedSpatialOperation

If the strategy does not support the SpatialOperation in args.
| Improve this Doc View Source

MakeQuery(SpatialArgs)

Make a Query based principally on SpatialOperation and 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
ConstantScoreQuery
Exceptions
Type Condition
UnsupportedSpatialOperation

If the strategy does not support the SpatialOperation in args.
| Improve this Doc View Source

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
IShape queryShape
Returns
Type Description
ValueSource
| Improve this Doc View Source

ToString()

Declaration
public override string ToString()
Returns
Type Description
System.String