Class SpatialPrefixTree
- java.lang.Object
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- org.apache.lucene.spatial.prefix.tree.SpatialPrefixTree
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- Direct Known Subclasses:
GeohashPrefixTree
,NumberRangePrefixTree
,QuadPrefixTree
,S2PrefixTree
public abstract class SpatialPrefixTree extends Object
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.
- WARNING: This API is experimental and might change in incompatible ways in the next release.
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Constructor Summary
Constructors Constructor Description SpatialPrefixTree(org.locationtech.spatial4j.context.SpatialContext ctx, int maxLevels)
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Method Summary
All Methods Instance Methods Abstract Methods Concrete Methods Modifier and Type Method Description abstract double
getDistanceForLevel(int level)
Given a cell having the specified level, returns the distance from opposite corners.abstract 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).int
getMaxLevels()
org.locationtech.spatial4j.context.SpatialContext
getSpatialContext()
CellIterator
getTreeCellIterator(org.locationtech.spatial4j.shape.Shape shape, int detailLevel)
Gets the intersecting cells for the specified shape, without exceeding detail level.abstract Cell
getWorldCell()
Returns the level 0 cell which encompasses all spatial data.abstract Cell
readCell(BytesRef term, Cell scratch)
This creates a new Cell (or re-usingscratch
if provided), initialized to the state as read by the bytes.String
toString()
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Method Detail
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getSpatialContext
public org.locationtech.spatial4j.context.SpatialContext getSpatialContext()
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getMaxLevels
public int getMaxLevels()
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getLevelForDistance
public abstract 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). Consequentlydist
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.- Parameters:
dist
->= 0
- Returns:
- level [1 to maxLevels]
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getDistanceForLevel
public abstract double getDistanceForLevel(int level)
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.- Parameters:
level
- [1 to maxLevels]- Returns:
> 0
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getWorldCell
public abstract Cell getWorldCell()
Returns the level 0 cell which encompasses all spatial data. Equivalent toreadCell(BytesRef,Cell)
with no bytes.
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readCell
public abstract Cell readCell(BytesRef term, Cell scratch)
This creates a new Cell (or re-usingscratch
if provided), initialized to the state as read by the bytes. Warning: An implementation may refer to the same byte array (no copy). IfCell.setLeaf()
is subsequently called, it would then modify these bytes.
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getTreeCellIterator
public CellIterator getTreeCellIterator(org.locationtech.spatial4j.shape.Shape shape, int detailLevel)
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.
- Parameters:
shape
- the shape; possibly null but the caller should liberally callremove()
if so.detailLevel
- the maximum detail level to get cells for- Returns:
- the matching cells
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