Class PrefixTreeStrategy

An abstract SpatialStrategy based on SpatialPrefixTree. The two subclasses are RecursivePrefixTreeStrategy and TermQueryPrefixTreeStrategy. This strategy is most effective as a fast approximate spatial search filter.

Characteristics:

• Can index any shape; however only RecursivePrefixTreeStrategy can effectively search non-point shapes.
• Can index a variable number of shapes per field value. This strategy can do it via multiple calls to CreateIndexableFields(IShape) for a document or by giving it some sort of Shape aggregate (e.g. NTS WKT MultiPoint). The shape's boundary is approximated to a grid precision.
• Can query with any shape. The shape's boundary is approximated to a grid precision.
• Only Intersects is supported. If only points are indexed then this is effectively equivalent to IsWithin.
• The strategy supports MakeDistanceValueSource(IPoint, double) even for multi-valued data, so long as the indexed data is all points; the behavior is undefined otherwise. However, it will likely be removed in the future in lieu of using another strategy with a more scalable implementation. Use of this call is the only circumstance in which a cache is used. The cache is simple but as such it doesn't scale to large numbers of points nor is it real-time-search friendly.

Implementation:

The SpatialPrefixTree does most of the work, for example returning a list of terms representing grids of various sizes for a supplied shape. An important configuration item is DistErrPct which balances shape precision against scalability. See those docs.

Note

This API is for internal purposes only and might change in incompatible ways in the next release.

Inheritance

object

SpatialStrategy

PrefixTreeStrategy

RecursivePrefixTreeStrategy

TermQueryPrefixTreeStrategy

Inherited Members

SpatialStrategy.m_ctx

SpatialStrategy.SpatialContext

SpatialStrategy.FieldName

SpatialStrategy.MakeDistanceValueSource(IPoint)

SpatialStrategy.MakeQuery(SpatialArgs)

SpatialStrategy.MakeFilter(SpatialArgs)

SpatialStrategy.MakeRecipDistanceValueSource(IShape)

SpatialStrategy.ToString()

object.Equals(object)

object.Equals(object, object)

object.GetHashCode()

object.GetType()

object.MemberwiseClone()

object.ReferenceEquals(object, object)

Namespace: Lucene.Net.Spatial.Prefix

Assembly: Lucene.Net.Spatial.dll

Syntax

public abstract class PrefixTreeStrategy : SpatialStrategy

Constructors

PrefixTreeStrategy(SpatialPrefixTree, string, bool)

An abstract SpatialStrategy based on SpatialPrefixTree. The two subclasses are RecursivePrefixTreeStrategy and TermQueryPrefixTreeStrategy. This strategy is most effective as a fast approximate spatial search filter.

Characteristics:

• Can index any shape; however only RecursivePrefixTreeStrategy can effectively search non-point shapes.
• Can index a variable number of shapes per field value. This strategy can do it via multiple calls to CreateIndexableFields(IShape) for a document or by giving it some sort of Shape aggregate (e.g. NTS WKT MultiPoint). The shape's boundary is approximated to a grid precision.
• Can query with any shape. The shape's boundary is approximated to a grid precision.
• Only Intersects is supported. If only points are indexed then this is effectively equivalent to IsWithin.
• The strategy supports MakeDistanceValueSource(IPoint, double) even for multi-valued data, so long as the indexed data is all points; the behavior is undefined otherwise. However, it will likely be removed in the future in lieu of using another strategy with a more scalable implementation. Use of this call is the only circumstance in which a cache is used. The cache is simple but as such it doesn't scale to large numbers of points nor is it real-time-search friendly.

Implementation:

The SpatialPrefixTree does most of the work, for example returning a list of terms representing grids of various sizes for a supplied shape. An important configuration item is DistErrPct which balances shape precision against scalability. See those docs.

Note

This API is for internal purposes only and might change in incompatible ways in the next release.

Declaration

protected PrefixTreeStrategy(SpatialPrefixTree grid, string fieldName, bool simplifyIndexedCells)

Parameters

Type	Name	Description
SpatialPrefixTree	grid
string	fieldName
bool	simplifyIndexedCells

Fields

FIELD_TYPE

Indexed, tokenized, not stored.

Declaration

public static readonly FieldType FIELD_TYPE

Field Value

Type	Description
FieldType

m_defaultFieldValuesArrayLen

An abstract SpatialStrategy based on SpatialPrefixTree. The two subclasses are RecursivePrefixTreeStrategy and TermQueryPrefixTreeStrategy. This strategy is most effective as a fast approximate spatial search filter.

Characteristics:

• Can index any shape; however only RecursivePrefixTreeStrategy can effectively search non-point shapes.
• Can index a variable number of shapes per field value. This strategy can do it via multiple calls to CreateIndexableFields(IShape) for a document or by giving it some sort of Shape aggregate (e.g. NTS WKT MultiPoint). The shape's boundary is approximated to a grid precision.
• Can query with any shape. The shape's boundary is approximated to a grid precision.
• Only Intersects is supported. If only points are indexed then this is effectively equivalent to IsWithin.
• The strategy supports MakeDistanceValueSource(IPoint, double) even for multi-valued data, so long as the indexed data is all points; the behavior is undefined otherwise. However, it will likely be removed in the future in lieu of using another strategy with a more scalable implementation. Use of this call is the only circumstance in which a cache is used. The cache is simple but as such it doesn't scale to large numbers of points nor is it real-time-search friendly.

Implementation:

The SpatialPrefixTree does most of the work, for example returning a list of terms representing grids of various sizes for a supplied shape. An important configuration item is DistErrPct which balances shape precision against scalability. See those docs.

Note

This API is for internal purposes only and might change in incompatible ways in the next release.

Declaration

protected int m_defaultFieldValuesArrayLen

Field Value

Type	Description
int

m_distErrPct

An abstract SpatialStrategy based on SpatialPrefixTree. The two subclasses are RecursivePrefixTreeStrategy and TermQueryPrefixTreeStrategy. This strategy is most effective as a fast approximate spatial search filter.

Characteristics:

• Can index any shape; however only RecursivePrefixTreeStrategy can effectively search non-point shapes.
• Can index a variable number of shapes per field value. This strategy can do it via multiple calls to CreateIndexableFields(IShape) for a document or by giving it some sort of Shape aggregate (e.g. NTS WKT MultiPoint). The shape's boundary is approximated to a grid precision.
• Can query with any shape. The shape's boundary is approximated to a grid precision.
• Only Intersects is supported. If only points are indexed then this is effectively equivalent to IsWithin.
• The strategy supports MakeDistanceValueSource(IPoint, double) even for multi-valued data, so long as the indexed data is all points; the behavior is undefined otherwise. However, it will likely be removed in the future in lieu of using another strategy with a more scalable implementation. Use of this call is the only circumstance in which a cache is used. The cache is simple but as such it doesn't scale to large numbers of points nor is it real-time-search friendly.

Implementation:

The SpatialPrefixTree does most of the work, for example returning a list of terms representing grids of various sizes for a supplied shape. An important configuration item is DistErrPct which balances shape precision against scalability. See those docs.

Note

This API is for internal purposes only and might change in incompatible ways in the next release.

Declaration

protected double m_distErrPct

Field Value

Type	Description
double

m_grid

An abstract SpatialStrategy based on SpatialPrefixTree. The two subclasses are RecursivePrefixTreeStrategy and TermQueryPrefixTreeStrategy. This strategy is most effective as a fast approximate spatial search filter.

Characteristics:

• Can index any shape; however only RecursivePrefixTreeStrategy can effectively search non-point shapes.
• Can index a variable number of shapes per field value. This strategy can do it via multiple calls to CreateIndexableFields(IShape) for a document or by giving it some sort of Shape aggregate (e.g. NTS WKT MultiPoint). The shape's boundary is approximated to a grid precision.
• Can query with any shape. The shape's boundary is approximated to a grid precision.
• Only Intersects is supported. If only points are indexed then this is effectively equivalent to IsWithin.
• The strategy supports MakeDistanceValueSource(IPoint, double) even for multi-valued data, so long as the indexed data is all points; the behavior is undefined otherwise. However, it will likely be removed in the future in lieu of using another strategy with a more scalable implementation. Use of this call is the only circumstance in which a cache is used. The cache is simple but as such it doesn't scale to large numbers of points nor is it real-time-search friendly.

Implementation:

The SpatialPrefixTree does most of the work, for example returning a list of terms representing grids of various sizes for a supplied shape. An important configuration item is DistErrPct which balances shape precision against scalability. See those docs.

Note

This API is for internal purposes only and might change in incompatible ways in the next release.

Declaration

protected readonly SpatialPrefixTree m_grid

Field Value

Type	Description
SpatialPrefixTree

m_simplifyIndexedCells

An abstract SpatialStrategy based on SpatialPrefixTree. The two subclasses are RecursivePrefixTreeStrategy and TermQueryPrefixTreeStrategy. This strategy is most effective as a fast approximate spatial search filter.

Characteristics:

• Can index any shape; however only RecursivePrefixTreeStrategy can effectively search non-point shapes.
• Can index a variable number of shapes per field value. This strategy can do it via multiple calls to CreateIndexableFields(IShape) for a document or by giving it some sort of Shape aggregate (e.g. NTS WKT MultiPoint). The shape's boundary is approximated to a grid precision.
• Can query with any shape. The shape's boundary is approximated to a grid precision.
• Only Intersects is supported. If only points are indexed then this is effectively equivalent to IsWithin.
• The strategy supports MakeDistanceValueSource(IPoint, double) even for multi-valued data, so long as the indexed data is all points; the behavior is undefined otherwise. However, it will likely be removed in the future in lieu of using another strategy with a more scalable implementation. Use of this call is the only circumstance in which a cache is used. The cache is simple but as such it doesn't scale to large numbers of points nor is it real-time-search friendly.

Implementation:

The SpatialPrefixTree does most of the work, for example returning a list of terms representing grids of various sizes for a supplied shape. An important configuration item is DistErrPct which balances shape precision against scalability. See those docs.

Note

This API is for internal purposes only and might change in incompatible ways in the next release.

Declaration

protected readonly bool m_simplifyIndexedCells

Field Value

Type	Description
bool

Properties

DefaultFieldValuesArrayLen

A memory hint used by MakeDistanceValueSource(IPoint) for how big the initial size of each Document's array should be. The default is 2. Set this to slightly more than the default expected number of points per document.

Declaration

public virtual int DefaultFieldValuesArrayLen { get; set; }

Property Value

Type	Description
int

DistErrPct

The default measure of shape precision affecting shapes at index and query times.

Declaration

public virtual double DistErrPct { get; set; }

Property Value

Type	Description
double

Remarks

The default measure of shape precision affecting shapes at index and query times. Points don't use this as they are always indexed at the configured maximum precision (MaxLevels); this applies to all other shapes. Specific shapes at index and query time can use something different than this default value. If you don't set a default then the default is DEFAULT_DISTERRPCT -- 2.5%.

See Also

DistErrPct

Grid

An abstract SpatialStrategy based on SpatialPrefixTree. The two subclasses are RecursivePrefixTreeStrategy and TermQueryPrefixTreeStrategy. This strategy is most effective as a fast approximate spatial search filter.

Characteristics:

• Can index any shape; however only RecursivePrefixTreeStrategy can effectively search non-point shapes.
• Can index a variable number of shapes per field value. This strategy can do it via multiple calls to CreateIndexableFields(IShape) for a document or by giving it some sort of Shape aggregate (e.g. NTS WKT MultiPoint). The shape's boundary is approximated to a grid precision.
• Can query with any shape. The shape's boundary is approximated to a grid precision.
• Only Intersects is supported. If only points are indexed then this is effectively equivalent to IsWithin.
• The strategy supports MakeDistanceValueSource(IPoint, double) even for multi-valued data, so long as the indexed data is all points; the behavior is undefined otherwise. However, it will likely be removed in the future in lieu of using another strategy with a more scalable implementation. Use of this call is the only circumstance in which a cache is used. The cache is simple but as such it doesn't scale to large numbers of points nor is it real-time-search friendly.

Implementation:

The SpatialPrefixTree does most of the work, for example returning a list of terms representing grids of various sizes for a supplied shape. An important configuration item is DistErrPct which balances shape precision against scalability. See those docs.

Note

This API is for internal purposes only and might change in incompatible ways in the next release.

Declaration

public virtual SpatialPrefixTree Grid { get; }

Property Value

Type	Description
SpatialPrefixTree

Methods

CreateIndexableFields(IShape)

Returns the IndexableField(s) from the shape that are to be added to the Lucene.Net.Documents.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 override Field[] CreateIndexableFields(IShape shape)

Parameters

Type	Name	Description
IShape	shape

Returns

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

Overrides

SpatialStrategy.CreateIndexableFields(IShape)

Exceptions

Type	Condition
NotSupportedException	if given a shape incompatible with the strategy

CreateIndexableFields(IShape?, double)

An abstract SpatialStrategy based on SpatialPrefixTree. The two subclasses are RecursivePrefixTreeStrategy and TermQueryPrefixTreeStrategy. This strategy is most effective as a fast approximate spatial search filter.

Characteristics:

• Can index any shape; however only RecursivePrefixTreeStrategy can effectively search non-point shapes.
• Can index a variable number of shapes per field value. This strategy can do it via multiple calls to CreateIndexableFields(IShape) for a document or by giving it some sort of Shape aggregate (e.g. NTS WKT MultiPoint). The shape's boundary is approximated to a grid precision.
• Can query with any shape. The shape's boundary is approximated to a grid precision.
• Only Intersects is supported. If only points are indexed then this is effectively equivalent to IsWithin.
• The strategy supports MakeDistanceValueSource(IPoint, double) even for multi-valued data, so long as the indexed data is all points; the behavior is undefined otherwise. However, it will likely be removed in the future in lieu of using another strategy with a more scalable implementation. Use of this call is the only circumstance in which a cache is used. The cache is simple but as such it doesn't scale to large numbers of points nor is it real-time-search friendly.

Implementation:

The SpatialPrefixTree does most of the work, for example returning a list of terms representing grids of various sizes for a supplied shape. An important configuration item is DistErrPct which balances shape precision against scalability. See those docs.

Note

This API is for internal purposes only and might change in incompatible ways in the next release.

Declaration

public virtual Field[] CreateIndexableFields(IShape? shape, double distErr)

Parameters

Type	Name	Description
IShape	shape
double	distErr

Returns

Type	Description
Field[]

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 override ValueSource MakeDistanceValueSource(IPoint queryPoint, double multiplier)

Parameters

Type	Name	Description
IPoint	queryPoint
double	multiplier

Returns

Type	Description
ValueSource

Overrides

SpatialStrategy.MakeDistanceValueSource(IPoint, double)