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Neo4j Spatial is a library facilitating the import, storage and querying of spatial data in the Neo4j open source graph database.

This projects manual is deployed as part of the local build as the Neo4j Spatial Manual.

Open Street Map

History

This library began as a collaborative vision between Neo-Technology and Craig Taverner in early 2010. The bulk of the initial work was done by Davide Savazzi as part of his 2010 Google Summer of Code (GSoC) project with Craig as mentor, as a project within the OSGeo GSoC program. In 2011 and 2012 two further GSoC projects contributed, the last of which saw Davide return as mentor.

The original vision for the library was a comprehensive suite of GIS capabilities somewhat inspired by PostGIS, while remaining aligned with the graph-nature of the underlying Neo4j database. To achieve this lofty goal the JTS and GeoTools libraries were used, giving a large suite of capabilities very early on.

However, back in 2010 Neo4j was an embedded database with deployments that saw a low level of concurrent operation. However, for many years now, Neo4j has been primarily deployed in high concurrent server environments. Over the years there have been various efforts to make the library more appropriate for use in these environments:

However, despite all these improvements, the core of the library only exposes the rich capabilities of JTS and GeoTools if used in an embedded environment. The large effort required to port the library to Neo4j 4.0 resulted in many backwards incompatibilities and highlighted the need for a new approach to spatial libraries for Neo4j.

Neo4j 4.x Support

This library was originally written in 2010 when Neo4j was still releasing early 1.x versions. This means it made use of internal Java API's that were deprecated over the years, some as early as Neo4j 2.x. When Neo4j 4.0 was released, many deprecated APIs were entirely removed. And the transaction API was changed in a fundamental way. This has meant that the spatial library needed a major refactoring to work with Neo4j 4.x:

Consequences of the port to Neo4j 4.x:

This last point means that you need to set the following in your neo4j.conf file:

dbms.security.procedures.unrestricted=spatial.*

If you are concerned about the security implications of unrestricted access, my best advice is to review the code and decide for yourself the level of risk you face. See, for example, the method IndexAccessMode.withIndexCreate, which adds index create capabilities to the security model. This means that users without index creation privileges will be able to create the necessary spatial support indexes described above. This code was not written because we wanted to allow for that case, it was written because in the Neo4j security model, procedures that can write data (mode=WRITE) are not allowed to create indexes. So this security-fix was required even in the Community Edition of Neo4j.

The rest of the README might have information that is no longer accurate for the current version of this library. Please report any mistakes as issues, or consider raising a pull-request with an appropriate fix.

Concept Overview

The key concepts of this library include:

Some key features include:

Index and Querying

The current index is an RTree index, but it has been developed in an extensible way allowing for other indices to be added if necessary. The spatial queries implemented are:

Building

The simplest way to build Neo4j Spatial is by using maven. Just clone the git repository and run

mvn install

This will download all dependencies, compiled the library, run the tests and install the artifact in your local repository. The spatial plugin will also be created in the target directory, and can be copied to your local server using instructions on the spatial server plugin below.

Layers and GeometryEncoders

The primary type that defines a collection of geometries is the Layer. A layer contains an index for querying. In addition, a Layer can be an EditableLayer if it is possible to add and modify geometries in the layer. The next most important interface is the GeometryEncoder.

The DefaultLayer is the standard layer, making use of the WKBGeometryEncoder for storing all geometry types as byte[] properties of one node per geometry instance.

The OSMLayer is a special layer supporting Open Street Map and storing the OSM model as a single fully connected graph. The set of Geometries provided by this layer includes Points, LineStrings and Polygons, and as such cannot be exported to Shapefile format, since that format only allows a single Geometry per layer. However, OMSLayer extends DynamicLayer, which allow it to provide any number of sub-layers, each with a specific geometry type and in addition based on an OSM tag filter. For example, you can have a layer providing all cycle paths as LineStrings, or a layer providing all lakes as Polygons. Underneath these are all still backed by the same fully connected graph, but exposed dynamically as apparently separate geometry layers.

Examples

Importing a shapefile

Spatial data is divided in Layers and indexed by a RTree.

GraphDatabaseService database = new GraphDatabaseFactory().newEmbeddedDatabase(storeDir);
try{
	ShapefileImporter importer = new ShapefileImporter(database);
	importer.importFile("roads.shp","layer_roads");
} finally {
	database.shutdown();
}

If using the server, the same can be achieved with spatial procedures (3.x only):

CALL spatial.addWKTLayer('layer_roads', 'geometry')
CALL spatial.importShapefileToLayer('layer_roads', 'roads.shp')

Importing an Open Street Map file

This is more complex because the current OSMImporter class runs in two phases, the first requiring a batch-inserter on the database. There is ongoing work to allow for a non-batch-inserter on the entire process, and possibly when you have read this that will already be available. Refer to the unit tests in classes TestDynamicLayers and TestOSMImport for the latest code for importing OSM data. At the time of writing the following worked:

OSMImporter importer = new OSMImporter("sweden");
Map<String, String> config = new HashMap<String, String>();
config.put("neostore.nodestore.db.mapped_memory", "90M" );
config.put("dump_configuration", "true");
config.put("use_memory_mapped_buffers", "true");
BatchInserter batchInserter = BatchInserters.inserter(new File(dir), config);
importer.importFile(batchInserter, "sweden.osm", false);
batchInserter.shutdown();

GraphDatabaseService db = new GraphDatabaseFactory().newEmbeddedDatabase(dir);
importer.reIndex(db, 10000);
db.shutdown();

Executing a spatial query

GraphDatabaseService database = new GraphDatabaseFactory().newEmbeddedDatabase(storeDir);
try {
	SpatialDatabaseService spatialService = new SpatialDatabaseService(database);
	Layer layer = spatialService.getLayer("layer_roads");
	SpatialIndexReader spatialIndex = layer.getIndex();
		
	Search searchQuery = new SearchIntersectWindow(new Envelope(xmin, xmax, ymin, ymax));
	spatialIndex.executeSearch(searchQuery);
	List<SpatialDatabaseRecord> results = searchQuery.getResults();
} finally {
	database.shutdown();
}

If using the server, the same can be achieved with spatial procedures (3.x only):

CALL spatial.bbox('layer_roads', {lon: 15.0, lat: 60.0}, {lon: 15.3, lat: 61.0})

Or using a polygon:


WITH 'POLYGON((15.3 60.2, 15.3 60.4, 15.7 60.4, 15.7 60.2, 15.3 60.2))' AS polygon
CALL spatial.intersects('layer_roads', polygon) YIELD node
RETURN node.name AS name

For further Java examples, refer to the test code in the LayersTest and the TestSpatial classes.

For further Procedures examples, refer to the code in the SpatialProceduresTest class.

Neo4j Spatial Geoserver Plugin

IMPORTANT: Examples in this readme were originally tested with GeoServer 2.1.1. However, regular testing of new releases of Neo4j Spatial against GeoServer is not done, and so we welcome feedback on which versions are known to work, and which ones do not, and perhaps some hints as to the errors or problems encountered.

Each release of Neo4j Spatial builds against a specific version of GeoTools and should then be used in the version of GeoServer that corresponds to that. The list of releases below starting at Neo4j 2.0.8 were built with GeoTools 9.0 for GeoServer 2.3.2, but most release for Neo4j 3.x were ported to GeoTools 14.4 for GeoServer 2.8.4.

For the port to Neo4j 4.0 we needed to upgrade GeoTools to 24.x to avoid bugs with older GeoTools in Java 11. This also required a complete re-write of the Neo4jDataStore and related classes. This has not been tested at all in any GeoTools enabled application, but could perhaps work with GeoServer 2.18.

Building

mvn clean install

Deployment into Geoserver

Testing in GeoServer trunk

svn co https://svn.codehaus.org/geoserver/trunk geoserver-trunk

cd geoserver-trunk
mvn clean install

cd src/web/app
mvn jetty:run

<profile>
	<id>neo4j</id>
	<dependencies>
		<dependency>
			<groupId>org.neo4j</groupId>
			<artifactId>neo4j-spatial</artifactId>
			<version>5.20.0</version>
		</dependency>
	</dependencies>
</profile>

The version specified on the version line can be changed to match the version you wish to work with (based on the version of Neo4j itself you are using). To see which versions are available see the list at Neo4j Spatial Releases.

    cd $GEOSERVER_SRC/src/web/app
    mvn jetty:run -Pneo4j

Using Neo4j Spatial with uDig

For more info head over to Neo4j Wiki on uDig (This wiki is currently dead, but there appears to be a working mirror in Japan at http://oss.infoscience.co.jp/neo4j/wiki.neo4j.org/content/Neo4j_Spatial_in_uDig.html).

Using the Neo4j Spatial Server plugin

The Neo4j Spatial Plugin is available for inclusion in the server version of Neo4j 2.x, Neo4j 3.x and Neo4j 4.x.

For versions up to 0.15-neo4j-2.3.4:

    #install the plugin
    unzip neo4j-spatial-XXXX-server-plugin.zip -d $NEO4J_HOME/plugins
    
    #start the server
    $NEO4J_HOME/bin/neo4j start

    #list REST API (edit to correct password)
    curl -u neo4j:neo4j http://localhost:7474/db/data/

For versions for neo4j 3.0 and later:

    #install the plugin
    cp neo4j-spatial-XXXX-server-plugin.jar $NEO4J_HOME/plugins/
    
    #start the server
    $NEO4J_HOME/bin/neo4j start

    #list REST API (edit to correct password)
    curl -u neo4j:neo4j http://localhost:7474/db/data/

    #list spatial procedures (edit to correct password)
    curl -u neo4j:neo4j -H "Content-Type: application/json" -X POST -d '{"query":"CALL spatial.procedures"}' http://localhost:7474/db/data/cypher

The server plugin provides access to the internal spatial capabilities using three APIs:

During the Neo4j 3.x releases, support for spatial procedures changed a little, through the addition of various new capabilities. They were very quickly much more capable than the older REST API, making them by far the best option for accessing Neo4j remotely or through Cypher.

The Java API (the original API for Neo4j Spatial) still remains, however, the most feature rich, and therefor we recommend that if you need to access Neo4j server remotely, and want deeper access to Spatial functions, consider writing your own Procedures. The Neo4j 3.0 documentation provides some good information on how to do this, and you can also refer to the Neo4j Spatial procedures source code for examples.

Building Neo4j spatial

git clone https://github.com/neo4j-contrib/spatial/spatial.git
cd spatial
mvn clean package

Building Neo4j Spatial Documentation

Add your GitHub credentials in your ~/.m2/settings.xml

<settings>
	<servers>
		<server>
			<id>github</id>
			<username>xxx@xxx.xx</username>
			<password>secret</password>
		</server>
	</servers>
</settings>

To build and deploy:

git clone https://github.com/neo4j/spatial.git
cd spatial
mvn clean install site -Pneo-docs-build

Using Neo4j spatial in your Java project with Maven

Add the following repositories and dependency to your project's pom.xml:

<dependency>
	<groupId>org.neo4j</groupId>
	<artifactId>neo4j-spatial</artifactId>
	<version>5.20.0</version>
</dependency>

The version specified on the last version line can be changed to match the version you wish to work with (based on the version of Neo4j itself you are using). To see which versions are available see the list at Neo4j Spatial Releases.

Running Neo4j spatial code from the command-line

Some of the classes in Neo4j-Spatial include main() methods and can be run on the command-line. For example there are command-line options for importing SHP and OSM data. See the main methods in the OSMImporter and ShapefileImporter classes. Here we will describe how to set up the dependencies for running the command-line, using the OSMImporter and the sample OSM file two-street.osm. We will show two ways to run this on the command line, one with the java command itself, and the other using the 'exec:java' target in maven. In both cases we use maven to set up the dependencies.

Compile

git clone git://github.com/neo4j-contrib/spatial.git
cd spatial
mvn clean compile

Run using JAVA command

mvn dependency:copy-dependencies
java -cp target/classes:target/dependency/* org.neo4j.gis.spatial.osm.OSMImporter osm-db two-street.osm

Note: On windows remember to separate the classpath with ';' instead of ':'.

The first command above only needs to be run once, to get a copy of all required JAR files into the directory target/dependency. Once this is done, all further java commands with the -cp specifying that directory will load all dependencies. It is likely that the specific command being run does not require all dependencies copied, since it will only be using parts of the Neo4j-Spatial library, but working out exactly which dependencies are required can take a little time, so the above approach is most certainly the easiest way to do this.

Run using 'mvn exec:java'

mvn exec:java -Dexec.mainClass=org.neo4j.gis.spatial.osm.OSMImporter -Dexec.args="osm-db two-street.osm"

Note that the OSMImporter cannot re-import the same data multiple times, so you need to delete the database between runs if you are planning to do that.