Package org.apache.lucene.spatial.prefix.tree

Class S2PrefixTree

  • public class S2PrefixTree
extends SpatialPrefixTree
    Spatial prefix tree for S2 Geometry. Shape factories for the given SpatialContext must implement the interface S2ShapeFactory. The tree can be configured on how it divided itself by providing an arity. The default arity is 1 which divided every sub-cell in 4 (except the first level that is always divided by 6) . Arity 2 divides sub-cells in 16 and arity 3 in 64 sub-cells.
    WARNING: This API is experimental and might change in incompatible ways in the next release.

    • Field Detail

      • arity

        protected final int arity

    • Constructor Detail

      • S2PrefixTree

        public S2PrefixTree​(org.locationtech.spatial4j.context.SpatialContext ctx,
                    int maxLevels)
        Creates a S2 spatial tree with arity 1.
        Parameters:
        ctx - The provided spatial context. The shape factor of the spatial context must implement S2ShapeFactory
        maxLevels - The provided maximum level for this tree.

      • S2PrefixTree

        public S2PrefixTree​(org.locationtech.spatial4j.context.SpatialContext ctx,
                    int maxLevels,
                    int arity)
        Creates a S2 spatial tree with provided arity.
        Parameters:
        ctx - The provided spatial context. The shape factor of the spatial context must implement S2ShapeFactory
        maxLevels - The provided maximum level for this tree.
        arity - The arity of the tree.

    • Method Detail

      • getMaxLevels

        public static int getMaxLevels​(int arity)
        Get max levels for this spatial tree.
        Parameters:
        arity - The arity of the tree.
        Returns:
        The maximum number of levels by the provided arity.

      • 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]

      • 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