Lucene Spatial

For now the Index Engine can only index Points. Other Shapes like rectangles and polygons will be added in the future.

How to create a Spatial Index

The index can be created on a Class that has two fields declared as Double (latitude,longitude) that are the coordinates of the Point.

For example we have a Class Place with 2 double fields latitude and longitude. To create the spatial index on City use this syntax.

CREATE INDEX Place.l_lon ON Place(latitude,longitude) SPATIAL ENGINE LUCENE

The Index can also be created with the Java Api. Example:

OSchema schema = databaseDocumentTx.getMetadata().getSchema();
OClass oClass = schema.createClass("Place");
oClass.createProperty("latitude", OType.DOUBLE);
oClass.createProperty("longitude", OType.DOUBLE);
oClass.createProperty("name", OType.STRING);
oClass.createIndex("Place.latitude_longitude", "SPATIAL", null, null, "LUCENE", new String[] { "latitude", "longitude" });

How to query the Spatial Index

Two custom operators has been added to query the Spatial Index:

1. NEAR: to find all Points near a given location (latitude, longitude)
2. WITHIN: to find all Points that are within a given Shape

NEAR operator

Finds all Points near a given location (latitude, longitude).

Syntax

select from Class where [<lat-field>,<long-field>] NEAR [<x>,<y>]

To specify maxDistance we have to pass a special variable in the context:

select  from Class where [<lat-field>,<long-field>,$spatial] NEAR [<x>,<y>,{"maxDistance": distance}]

The 'maxDistance' field has to be in kilometers, not radians. Results are sorted from nearest to farthest.

To know the exact distance between your Point and the Points matched, use the special variable in the context $distance.

select *, $distance from Class where [<lat-field>,<long-field>,$spatial] NEAR [<x>,<y>,{"maxDistance": distance}]

Examples

Let's take the example we have written before. We have a Spatial Index on Class Place on properties latitude and longitude.

Example: How to find the nearest Place of a given point:

select *,$distance from Place where [latitude,longitude,$spatial] NEAR [51.507222,-0.1275,{"maxDistance":1}]

WITHIN operator

Finds all Points that are within a given Shape.

	The current release supports only Bounding Box shape

Syntax

select  from Class where [<lat field>,<long field>] WITHIN [ [ <lng1>, <lat1> ] , [ <lng2>, <lat2> ] ... ]

Examples

Example with previous configuration:

select * from Places where [latitude,longitude] WITHIN [[51.507222,-0.1275],[55.507222,-0.1275]]

This query will return all Places within the given Bounding Box.

Future Plans

• Index All types of shape
• Adding more operators such as INTERSECT
• Extend the WITHIN operator to support not only Bounding Box