Namespace Lucene.Net.Spatial

The Spatial Module for Apache Lucene.NET

The spatial module is new to Lucene.NET 4, replacing the old "Lucene.Net.Contrib" module that came before it. The principle interface to the module is a SpatialStrategy which encapsulates an approach to indexing and searching based on shapes. Different Strategies have different features and performance profiles, which are documented at each Strategy implementation class level.

For some sample code showing how to use the API, see SpatialExample.cs in the tests.

The spatial module uses Spatial4n, a .NET port of the ASL licensed Spatial4j heavily. Spatial4n is a library with these capabilities:

  • Provides shape implementations, namely point, rectangle, and circle. Both geospatial contexts and plain 2D Euclidean/Cartesian contexts are supported. With an additional dependency, it adds polygon and other geometry shape support via integration with NetTopologySuite (often referred to as NTS). This includes dateline wrap support.
  • Shape parsing and serialization, including Well-Known Text (WKT) (via NTS).
  • Distance and other spatial related math calculations.
Note

Historical Fact: The new spatial module was once known as Lucene Spatial Playground (LSP) as an external project. In ~March 2012, LSP split into this new module as part of Lucene and Spatial4j externally. A large chunk of the LSP implementation originated as SOLR-2155 which uses trie/prefix-tree algorithms with a geohash encoding. That approach is implemented in RecursivePrefixTreeStrategy today.

Classes

DisjointSpatialFilter

A Spatial Filter implementing IsDisjointTo in terms of a SpatialStrategy's support for Intersects. A document is considered disjoint if it has spatial data that does not intersect with the query shape. Another way of looking at this is that it's a way to invert a query shape.

This is a Lucene.NET EXPERIMENTAL API, use at your own risk

SpatialStrategy

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 the FieldCache, or some other 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 is a Lucene.NET EXPERIMENTAL API, use at your own risk