org.apache.lucene.spatial.prefix.tree

Class GeohashPrefixTree

java.lang.Object

org.apache.lucene.spatial.prefix.tree.SpatialPrefixTree

org.apache.lucene.spatial.prefix.tree.GeohashPrefixTree

public class GeohashPrefixTree
extends SpatialPrefixTree

A SpatialPrefixTree based on Geohashes. Uses GeohashUtils to do all the geohash work.

WARNING: This API is experimental and might change in incompatible ways in the next release.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	GeohashPrefixTree.Factory Factory for creating GeohashPrefixTree instances with useful defaults

Field Summary

Fields inherited from class org.apache.lucene.spatial.prefix.tree.SpatialPrefixTree

ctx, maxLevels

Constructor Summary

Constructors

Constructor and Description
GeohashPrefixTree(org.locationtech.spatial4j.context.SpatialContext ctx, int maxLevels)

Method Summary

Modifier and Type	Method and Description
protected Cell	getCell(org.locationtech.spatial4j.shape.Point p, int level) Returns the cell containing point p at the specified level.
double	getDistanceForLevel(int level) Given a cell having the specified level, returns the distance from opposite corners.
int	getLevelForDistance(double dist) Returns the level of the largest grid in which its longest side is less than or equal to the provided distance (in degrees).
static int	getMaxLevelsPossible() Any more than this and there's no point (double lat and lon are the same).
CellIterator	getTreeCellIterator(org.locationtech.spatial4j.shape.Shape shape, int detailLevel) Gets the intersecting cells for the specified shape, without exceeding detail level.
Cell	getWorldCell() Returns the level 0 cell which encompasses all spatial data.
Cell	readCell(BytesRef term, Cell scratch) This creates a new Cell (or re-using scratch if provided), initialized to the state as read by the bytes.

Methods inherited from class org.apache.lucene.spatial.prefix.tree.SpatialPrefixTree

getMaxLevels, getSpatialContext, toString

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

GeohashPrefixTree

public GeohashPrefixTree(org.locationtech.spatial4j.context.SpatialContext ctx,
                         int maxLevels)

Method Detail

getMaxLevelsPossible

public static int getMaxLevelsPossible()

Any more than this and there's no point (double lat and lon are the same).

getWorldCell

public Cell getWorldCell()

Description copied from class: SpatialPrefixTree

Returns the level 0 cell which encompasses all spatial data. Equivalent to SpatialPrefixTree.readCell(BytesRef,Cell) with no bytes.

Specified by:

getWorldCell in class SpatialPrefixTree

getLevelForDistance

public int getLevelForDistance(double dist)

Description copied from class: SpatialPrefixTree

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.

Specified by:

getLevelForDistance in class SpatialPrefixTree

Parameters:

dist - >= 0

Returns:

level [1 to maxLevels]

getCell

protected Cell getCell(org.locationtech.spatial4j.shape.Point p,
                       int level)

Returns the cell containing point p at the specified level.

getDistanceForLevel

public double getDistanceForLevel(int level)

Description copied from class: SpatialPrefixTree

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

Specified by:

getDistanceForLevel in class SpatialPrefixTree

Parameters:

level - [1 to maxLevels]

Returns:

> 0

readCell

public Cell readCell(BytesRef term,
                     Cell scratch)

Description copied from class: SpatialPrefixTree

This creates a new Cell (or re-using scratch if provided), initialized to the state as read by the bytes. Warning: An implementation may refer to the same byte array (no copy). If Cell.setLeaf() is subsequently called, it would then modify these bytes.

Specified by:

readCell in class SpatialPrefixTree

getTreeCellIterator

public CellIterator getTreeCellIterator(org.locationtech.spatial4j.shape.Shape shape,
                                        int detailLevel)

Description copied from class: SpatialPrefixTree

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. For cells at detailLevel, they are marked as leaves too, unless it's a point.

IMPORTANT: Cells returned from the iterator can be re-used for cells at the same level. So you can't simply iterate to subsequent cells and still refer to the former cell nor the bytes returned from the former cell, unless you know the former cell is a parent.

Overrides:

getTreeCellIterator in class SpatialPrefixTree

Parameters:

shape - the shape; possibly null but the caller should liberally call remove() if so.

detailLevel - the maximum detail level to get cells for

Returns:

the matching cells