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
`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

All Methods Static Methods Instance Methods Concrete Methods
`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