Class SpatialPrefixTree

A spatial Prefix Tree, or Trie, which decomposes shapes into prefixed strings at variable lengths corresponding to variable precision.

Inheritance

System.Object

SpatialPrefixTree

GeohashPrefixTree

QuadPrefixTree

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.Prefix.Tree

Assembly: Lucene.Net.Spatial.dll

Syntax

public abstract class SpatialPrefixTree

Remarks

A spatial Prefix Tree, or Trie, which decomposes shapes into prefixed strings at variable lengths corresponding to variable precision. Each string corresponds to a rectangular spatial region. This approach is also referred to "Grids", "Tiles", and "Spatial Tiers".

Implementations of this class should be thread-safe and immutable once initialized.

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

Constructors

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SpatialPrefixTree(SpatialContext, Int32)

Declaration

public SpatialPrefixTree(SpatialContext ctx, int maxLevels)

Parameters

Type	Name	Description
Spatial4n.Core.Context.SpatialContext	ctx
System.Int32	maxLevels

Fields

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m_ctx

Declaration

protected readonly SpatialContext m_ctx

Field Value

Type	Description
Spatial4n.Core.Context.SpatialContext

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m_maxLevels

Declaration

protected readonly int m_maxLevels

Field Value

Type	Description
System.Int32

Properties

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MaxLevels

Declaration

public virtual int MaxLevels { get; }

Property Value

Type	Description
System.Int32

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SpatialContext

Declaration

public virtual SpatialContext SpatialContext { get; }

Property Value

Type	Description
Spatial4n.Core.Context.SpatialContext

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WorldCell

Returns the level 0 cell which encompasses all spatial data.

Declaration

public virtual Cell WorldCell { get; }

Property Value

Type	Description
Cell

Remarks

Returns the level 0 cell which encompasses all spatial data. Equivalent to GetCell(String) with System.String.Empty. This cell is threadsafe, just like a spatial prefix grid is, although cells aren't generally threadsafe.

Methods

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CellsToTokenStrings(ICollection<Cell>)

Will add the trailing leaf byte for leaves. This isn't particularly efficient.

Declaration

[Obsolete("TODO remove; not used and not interesting, don't need collection in & out")]
public static IList<string> CellsToTokenStrings(ICollection<Cell> cells)

Parameters

Type	Name	Description
System.Collections.Generic.ICollection<Cell>	cells

Returns

Type	Description
System.Collections.Generic.IList<System.String>

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GetCell(IPoint, Int32)

Returns the cell containing point p at the specified level.

Declaration

protected virtual Cell GetCell(IPoint p, int level)

Parameters

Type	Name	Description
Spatial4n.Core.Shapes.IPoint	p
System.Int32	level

Returns

Type	Description
Cell

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GetCell(Byte[], Int32, Int32)

Declaration

public abstract Cell GetCell(byte[] bytes, int offset, int len)

Parameters

Type	Name	Description
System.Byte[]	bytes
System.Int32	offset
System.Int32	len

Returns

Type	Description
Cell

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GetCell(Byte[], Int32, Int32, Cell)

Declaration

public Cell GetCell(byte[] bytes, int offset, int len, Cell target)

Parameters

Type	Name	Description
System.Byte[]	bytes
System.Int32	offset
System.Int32	len
Cell	target

Returns

Type	Description
Cell

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GetCell(String)

The cell for the specified token.

Declaration

public abstract Cell GetCell(string token)

Parameters

Type	Name	Description
System.String	token

Returns

Type	Description
Cell

Remarks

The cell for the specified token. The empty string should be equal to WorldCell. Precondition: Never called when token length > maxLevel.

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GetCells(IPoint, Int32, Boolean)

A Point-optimized implementation of GetCells(IShape, Int32, Boolean, Boolean). That method in facts calls this for points.

This implementation depends on GetCell(String) being fast, as its called repeatedly when incPlarents is true.

Declaration

public virtual IList<Cell> GetCells(IPoint p, int detailLevel, bool inclParents)

Parameters

Type	Name	Description
Spatial4n.Core.Shapes.IPoint	p
System.Int32	detailLevel
System.Boolean	inclParents

Returns

Type	Description
System.Collections.Generic.IList<Cell>

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GetCells(IShape, Int32, Boolean, Boolean)

Gets the intersecting cells for the specified shape, without exceeding detail level.

Declaration

public virtual IList<Cell> GetCells(IShape shape, int detailLevel, bool inclParents, bool simplify)

Parameters

Type	Name	Description
Spatial4n.Core.Shapes.IShape	shape	the shape; non-null
System.Int32	detailLevel	the maximum detail level to get cells for
System.Boolean	inclParents	if true then all parent cells of leaves are returned too. The top world cell is never returned.
System.Boolean	simplify	for non-point shapes, this will simply/aggregate sets of complete leaves in a cell to its parent, resulting in ~20-25% fewer cells.

Returns

Type	Description
System.Collections.Generic.IList<Cell>	a set of cells (no dups), sorted, immutable, non-null

Remarks

Gets the intersecting cells for the specified shape, without exceeding detail level. If a cell is within the query shape then it's marked as a leaf and none of its children are added.

This implementation checks if shape is a Spatial4n.Core.Shapes.IPoint and if so returns GetCells(IPoint, Int32, Boolean).

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GetDistanceForLevel(Int32)

Given a cell having the specified level, returns the distance from opposite corners.

Declaration

public virtual double GetDistanceForLevel(int level)

Parameters

Type	Name	Description
System.Int32	level	[1 to maxLevels]

Returns

Type	Description
System.Double	0

Remarks

Given a cell having the specified level, returns the distance from opposite corners. Since this might very depending on where the cell is, this method may over-estimate.

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GetLevelForDistance(Double)

Returns the level of the largest grid in which its longest side is less than or equal to the provided distance (in degrees).

Declaration

public abstract int GetLevelForDistance(double dist)

Parameters

Type	Name	Description
System.Double	dist	= 0

Returns

Type	Description
System.Int32	level [1 to maxLevels]

Remarks

Returns the level of the largest grid in which its longest side is less than or equal to the provided distance (in degrees). Consequently dist acts as an error epsilon declaring the amount of detail needed in the grid, such that you can get a grid with just the right amount of precision.

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ToString()

Declaration

public override string ToString()

Returns

Type	Description
System.String

Overrides

System.Object.ToString()