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, UTF8

Constructor Summary

Constructors

Constructor and Description
GeohashPrefixTree(com.spatial4j.core.context.SpatialContext ctx, int maxLevels)

Method Summary

Methods

Modifier and Type	Method and Description
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 & lon are the same).
Node	getNode(byte[] bytes, int offset, int len)
Node	getNode(com.spatial4j.core.shape.Point p, int level)
Node	getNode(String token) The cell for the specified token.
List<Node>	getNodes(com.spatial4j.core.shape.Shape shape, int detailLevel, boolean inclParents) Gets the intersecting & including cells for the specified shape, without exceeding detail level.

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

getMaxLevels, getNode, getNodesAltPoint, getSpatialContext, getWorldNode, nodesToTokenStrings, toString

Methods inherited from class java.lang.Object

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

Constructor Detail

GeohashPrefixTree

public GeohashPrefixTree(com.spatial4j.core.context.SpatialContext ctx,
                 int maxLevels)

Method Detail

getMaxLevelsPossible

public static int getMaxLevelsPossible()

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

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]

getNode

public Node getNode(com.spatial4j.core.shape.Point p,
           int level)

Overrides:

getNode in class SpatialPrefixTree

getNode

public Node getNode(String token)

Description copied from class: SpatialPrefixTree

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

Specified by:

getNode in class SpatialPrefixTree

getNode

public Node getNode(byte[] bytes,
           int offset,
           int len)

Specified by:

getNode in class SpatialPrefixTree

getNodes

public List<Node> getNodes(com.spatial4j.core.shape.Shape shape,
                  int detailLevel,
                  boolean inclParents)

Description copied from class: SpatialPrefixTree

Gets the intersecting & including cells for the specified shape, without exceeding detail level. The result is a set of cells (no dups), sorted. Unmodifiable.

This implementation checks if shape is a Point and if so uses an implementation that recursively calls Node.getSubCell(com.spatial4j.core.shape.Point). Cell subclasses ideally implement that method with a quick implementation, otherwise, subclasses should override this method to invoke SpatialPrefixTree.getNodesAltPoint(com.spatial4j.core.shape.Point, int, boolean). TODO consider another approach returning an iterator -- won't build up all cells in memory.

Overrides:

getNodes in class SpatialPrefixTree