org.apache.lucene.spatial

Class SpatialStrategy

  • Direct Known Subclasses:
    BBoxStrategy, CompositeSpatialStrategy, PointVectorStrategy, PrefixTreeStrategy, SerializedDVStrategy


    public abstract class SpatialStrategy
    extends Object
    The SpatialStrategy encapsulates an approach to indexing and searching based on shapes.

    Different implementations will support different features. A strategy should document these common elements:

    • Can it index more than one shape per field?
    • What types of shapes can be indexed?
    • What types of query shapes can be used?
    • What types of query operations are supported? This might vary per shape.
    • Does it use some type of cache? When?
    If a strategy only supports certain shapes at index or query time, then in general it will throw an exception if given an incompatible one. It will not be coerced into compatibility.

    Note that a SpatialStrategy is not involved with the Lucene stored field values of shapes, which is immaterial to indexing and search.

    Thread-safe.

    This API is marked as experimental, however it is quite stable.

    • Field Detail

      • ctx

        protected final SpatialContext ctx
    • Constructor Detail

      • SpatialStrategy

        public SpatialStrategy(SpatialContext ctx,
                               String fieldName)
        Constructs the spatial strategy with its mandatory arguments.
    • Method Detail

      • getFieldName

        public String getFieldName()
        The name of the field or the prefix of them if there are multiple fields needed internally.
        Returns:
        Not null.
      • createIndexableFields

        public abstract Field[] createIndexableFields(Shape shape)
        Returns the IndexableField(s) from the shape that are to be added to the Document. These fields are expected to be marked as indexed and not stored.

        Note: If you want to store the shape as a string for retrieval in search results, you could add it like this:

        document.add(new StoredField(fieldName,ctx.toString(shape)));
        The particular string representation used doesn't matter to the Strategy since it doesn't use it.
        Returns:
        Not null nor will it have null elements.
        Throws:
        UnsupportedOperationException - if given a shape incompatible with the strategy
      • makeDistanceValueSource

        public ValueSource makeDistanceValueSource(Point queryPoint)
        See #makeDistanceValueSource(org.locationtech.spatial4j.shape.Point, double) called with a multiplier of 1.0 (i.e. units of degrees).
      • makeDistanceValueSource

        public abstract ValueSource makeDistanceValueSource(Point queryPoint,
                                                            double multiplier)
        Make a ValueSource returning the distance between the center of the indexed shape and queryPoint. If there are multiple indexed shapes then the closest one is chosen. The result is multiplied by multiplier, which conveniently is used to get the desired units.
      • makeRecipDistanceValueSource

        public final ValueSource makeRecipDistanceValueSource(Shape queryShape)
        Returns a ValueSource with values ranging from 1 to 0, depending inversely on the distance from #makeDistanceValueSource(org.locationtech.spatial4j.shape.Point,double). The formula is c/(d + c) where 'd' is the distance and 'c' is one tenth the distance to the farthest edge from the center. Thus the scores will be 1 for indexed points at the center of the query shape and as low as ~0.1 at its furthest edges.