Vertices and Edges

Similar to the Console interface, you can also create, manage and control vertices and edges through the Graph API.

Vertices

To create a new vertex in the current Graph Database instance, call the Vertex OrientGraph.addVertex(Object id) method. Note that this ignores the id parameter, given that the OrientDB implementation assigns a unique ID once it creates the vertex. To return the unique ID, run the Vertex.getId() method on the object.

For instance,

Vertex v = graph.addVertex(null);
System.out.println("Created vertex: " + v.getId());

Retrieving Vertices

To retrieve all vertices on the object, use the getVertices() method. For instance,

for (Vertex v : graph.getVertices()) {
    System.out.println(v.getProperty("name"));
}

To lookup vertices by a key, call the getVertices() method by passing the field name and the value to match. Remember that in order to use indexes, you should use the "class" dot (.) "property name" as field name. Example:

for( Vertex v : graph.getVertices("Account.id", "23876JS2") ) {
  System.out.println("Found vertex: " + v );
}

To know more about how to define indexes look at: Using Graph Indexes.

Removing Vertices

To remove a vertex from the current Graph Database, call the OrientGraph.removeVertex(Vertex vertex) method. This disconnects the vertex from the graph database and then removes it. Disconnection deletes all vertex edges as well.

For instance,

graph.removeVertex(luca);

Disconnects and removes the vertex luca.

Edges

Edges link two vertices in the database. The vertices must exist already. To create a new edge in the current Graph Database, call the Edge OrientGraph.addEdge(Object id, Vertex outVertex, Vertex inVertex, String label ) method.

Bear in mind that OrientDB ignores the id parameter, given that it assigns a unique ID when it creates the edge. To access this ID, use the Edge.getId() method. outVertex refers to the vertex instance where the edge starts and inVertex refers to where the edge ends. label indicates the edge label. Specify it as null if you don't want to assign a label.

For instance,

Vertex luca = graph.addVertex(null);
luca.setProperty("name", "Luca");

Vertex marko = graph.addVertex(null);
marko.setProperty("name", "Marko");

Edge lucaKnowsMarko = graph.addEdge(null, luca, marko, "knows");
System.out.println("Created edge: " + lucaKnowsMarko.getId());

For more information on optimizing edge creation through concurrent threads and clients, see Concurrency on Adding Edges.

Retrieving Edges

To retrieve all edges use the getEdges() method:

for (Edge e : graph.getEdges()) {
    System.out.println(e.getProperty("age"));
}

When using Lightweight Edges, OrientDB stores edges as links rather than records. This improves performance, but as a consequence, the .getEdges() method only retrieves records of the class E. When using Lightweight Edges, OrientDB only creates records in class E under certain circumstances, such as when the edge has properties. Otherwise, the edges exist as links on the in and out vertices.

If you want to use .getEdges() to return all edges, disable the Lightweight Edges feature by executing the following command:

orientdb> ALTER DATABASE my_db useLightweightEdges=FALSE

You only need to run this command once to disable Lightweight Edges. The change only takes effect on edges you create after running it. For existing edges, you need to convert them from links to actual edges before the .getEdges() method returns all edges. For more information, see Troubleshooting.

NOTE: Since version 2.0 of OrientDB, the Lightweight Edges feature is disabled by default.

Removing Edges

To remove an edge from the current Graph Database, call the OrientGraph.removeEdge(Edge edge) method. It removes the edge connecting two vertices.

For instance,

graph.removeEdge(lucaKnowsMarko);

Vertex and Edge Properties

Vertices and Edges can have multiple properties. The key to this property is a String, the value any Types supported by OrientDB.

For instance,

vertex2.setProperty("x", 30.0f);
vertex2.setProperty("y", ((float) vertex1.getProperty( "y" )) / 2);

for (String property : vertex2.getPropertyKeys()) {
      System.out.println("Property: " + property + "=" + vertex2.getProperty(property));
}

vertex1.removeProperty("y");

Setting Multiple Properties

The OrientDB implementation of the Blueprints extension supports setting multiple properties in one command against vertices and edges, using the setProperties(Object ...) method. This improves performance by allowing you to avoid saving the graph element each time you set a property.

For instance,

vertex.setProperties( "name", "Jill", "age", 33, "city", "Rome", "born", "Victoria, TX" );

You can also pass a Map of values as the first argument. In this case all map entries are set as element properties:

Map<String,Object> props = new HashMap<String,Object>();
props.put("name", "Jill");
props.put("age", 33);
props.put("city", "Rome");
props.put("born", "Victoria, TX");
vertex.setProperties(props);

Creating Element and Properties Together

In addition to the above methods, using the OrientDB Blueprint implementation, you can also set the initial properties while creating vertices or edges.

For instance,

• To create a vertex and set the initial properties:

  graph.addVertex("class:Customer", "name", "Jill", 
      "age", 33, "city", "Rome", "born", "Victoria, TX");
  

  This line creates a new vertex of the class Customer. It sets the initial properties for name, age, city, and born.

• The same procedure also works for edges.

  person1.addEdge("class:Friend", person1, person2, null, 
      "since", "2013-07-30");
  

  This creates an edge of the class Friend between the vertices person1 and person2 with the property since.

Both methods accept Map<String, Object> as a parameter, allowing you to set one property per map entry, such as in the above example.

Using Indices

OrientDB allows query execution against any field of a vertex or edge, indexed or non-indexed. To speed up queries, set up indices on key properties that use in the query.

• For instance, say that you have a query that looks for all vertices with the name OrientDB. For instance,

  graph.getVertices("name", "OrientDB");
  

• Without an index against the property name, this query can take up a lot of time. You can improve performance by creating a new index against the name property:

  graph.createKeyIndex("name", Vertex.class);
  

• In cases where the name must be unique, you can enforce this constraint by setting the index as UNIQUE. (This feature is only available in OrientDB).

  graph.createKeyIndex("name", Vertex.class, new Parameter("type", "UNIQUE"));
  

  It applies this constraint to vertices and sub-type instances.

• To create an index against a custom type, such as the Customer vertex, use the additional class parameter:

  graph.createKeyIndex("name", Vertex.class, new Parameter("class", "Customer"));
  

• You can also have both unique indices against custom types:

  graph.createKeyIndex("name", Vertex.class, new Parameter("type", "UNIQUE"), new Parameter("class", "Customer"));
  

• To create a case-insensitive index, use the collate parameter:

  graph.createKeyIndex("name", Vertex.class, new Parameter("type", "UNIQUE"), new Parameter("class", "Customer"),new Parameter("collate", "ci"));
  

• To get a vertex or edge by key prefix, use the class name before the property. For example above, you would use Customer.name instead of just name to create the index against the field of that class:

  for (Vertex v : graph.getVertices("Customer.name", "Jay")) {
      System.out.println("Found vertex: " + v);
  }
  

• In the event that the class name is not passed, it uses V for vertices and E for edges:

  graph.getVertices("name", "Jay");
  graph.getEdges("age", 20);
  

For more information, see Indexes.