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Neo4j Spatial

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

This project's manual is deployed to the Neo4j Labs page.

Versioning

Since version 5.19.0, the versioning of Neo4j Spatial is aligned with the versioning of Neo4j itself. This means that Neo4j Spatial 5.19.0 is build against Neo4j 5.19, and so on.

Installation

1. Copy the desired neo4j-spatial-server-plugin-x.x.x-with-dependencies.jar from the release page to your neo4j plugin directory.

2. set up your database with the following configuration in your neo4j.conf file:

   dbms.security.procedures.unrestricted=spatial.*
   

   NOTE: If you're concerned about the security risks of unrestricted access, we recommend reviewing the code to assess the level of risk for your use case. For example, the method IndexAccessMode.withIndexCreate grants index creation capabilities within the security model. This allows users without index creation privileges to generate the required spatial support indexes. This behavior was not intentionally designed to bypass security but was necessary due to Neo4j’s security model, where procedures with WRITE mode are not permitted to create indexes. As a result, this adjustment was required even in the Community Edition of Neo4j.

3. Restart your Neo4j server.

4. Run CALL spatial.procedures in the Neo4j browser to see the available spatial procedures.

Concept Overview

The key concepts of this library include:

• Allow the user to model geograph data in whatever way they wish, through providing an adapter ( extend GeometryEncoder). Built-in encoders include:
  • WKT and WKB stored as properties of nodes
  • Simple points as properties of nodes (two doubles, or a double[] or a native Neo4j Point)
  • OpenStreetMap with complex geometries stored as sub-graphs to reflect the original topology of the OSM model
• Multiple CoordinationReferenceSystem support using GeoTools
• Support the concept of multiple geographic layers, each with its own CRS and Index
• Include an index capable of searching for complex geometries (in-graph RTree index)
• Support import and export in a number of known formats (e.g. Shapefile and OSM)
• Embed the library and Neo4j within GIS tools like uDig and GeoServer

Some key features include:

• Utilities for importing from ESRI Shapefile as well as Open Street Map files
• Support for all the common geometry types
• An RTree index for fast searches on geometries
• Support for topology operations during the search (contains, within, intersects, covers, disjoint, etc.)
• The possibility to enable spatial operations on any graph of data, regardless of the way the spatial data is stored, as long as an adapter is provided to map from the graph to the geometries.
• Ability to split a single layer or dataset into multiple sub-layers or views with pre-configured filters
• Server Plugin for Neo4j Server 2.x and 3.x
  • REST API for creating layers and adding nodes or geometries to layers
  • IndexProvider API (2.x only) for Cypher access using START node=node:geom({query})
  • Procedures (3.x only) for much more comprehensive access to spatial from Cypher

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:

• Contain
• Cover
• Covered By
• Cross
• Disjoint
• Intersect
• Intersect Window
• Overlap
• Touch
• Within
• Within Distance

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 from the installation section.

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

• unzip the target/xxxx-server-plugin.zip and the Neo4j libraries from your Neo4j download under $NEO4J_HOME/lib into $GEOSERVER_HOME/webapps/geoserver/WEB-INF/lib
• restart geoserver
• configure a new workspace
• configure a new datasource neo4j in your workspace. Point the "The directory path of the Neo4j database:" parameter to the relative (form the GeoServer working dir) or absolute path to a Neo4j Spatial database with layers ( see Neo4j Spatial)
• in Layers, do "Add new resource" and choose your Neo4j datastore to see the existing Neo4j Spatial layers and add them.

Testing in GeoServer trunk

• check out the geoserver source

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

• build the source

cd geoserver-trunk
mvn clean install

• check that you can run the web app as of The GeoServer Maven build guide

cd src/web/app
mvn jetty:run

• in $GEOSERVER_SOURCE/src/web/app/pom.xml https://svn.codehaus.org/geoserver/trunk/src/web/app/pom.xml, add the following lines under the profiles section:

<profile>
	<id>neo4j</id>
	<dependencies>
		<dependency>
			<groupId>org.neo4j</groupId>
			<artifactId>neo4j-spatial</artifactId>
			<version>5.26.0</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.

• start the GeoServer webapp again with the added neo4j profile

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

• find Neo4j installed as a datasource under http://localhost:8080

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

• Procedures for much more comprehensive access to spatial from Cypher
  • Documentation is not yet available, but you can list the available procedures within Neo4j using the query CALL spatial.procedures
  • This API uses the Procedures capabilities released in Neo4j 3.0, and is therefor not available for Neo4j 2.x

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

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.