Vertices in a property graph

A vertex in a property graph is an object with:

  • A set of named properties.
  • A set of incoming edges.
  • A set of outgoing edges.

There are a few basic operations we need to perform on vertices in a property graph:

  • Create a vertex.
  • Delete a vertex.
  • Connect two vertices with edges.
  • Get/set the properties of a vertex.

Let's see how this is done in Pacer ...

Creating vertices

We create a vertex using the create_vertex method of the graph object.


You can delete a vertex from the graph by calling its delete! method.


  1. Like all methods that modify the graph, this methods must be called inside a transaction.
  2. When we delete a vertex, we also delete all of the edges that are attached to it.


You can add an edge to another vertex, by calling the add_edges_to method.

add_edges_to(edge_label, other_vertex, properties)

Create (and return) a new edge to other_vertex. The edge_label (symbol or string) argument is required, but properties (hash) is optional.

Vertices do not have a method to remove edges, we remove edges by deleting them from the graph.

Getting edges

Each of the methods below returns a route (i.e. collection) of vertices.


Get all outgoing edges of a vertex.


Get all incoming edges of a vertex.


Get both, incoming and outgoing, edges



jruby-1.7.19 :075 >
 => {"airport"=>"YYZ", "city"=>"Toronto"}

jruby-1.7.19 :076 > v[:airport]
 => "YYZ" 

jruby-1.7.19 :077 > v['city']
 => "Toronto" 

jruby-1.7.19 :078 > v[:foo]
 => nil 

jruby-1.7.19 :079 > v['foo'] = 'bar'
 => "bar" 

jruby-1.7.19 :080 >
 => {"airport"=>"YYZ", "foo"=>"bar", "city"=>"Toronto"} 

jruby-1.7.19 :081 > v[:foo] = nil
 => nil 

jruby-1.7.19 :082 >
 => {"airport"=>"YYZ", "city"=>"Toronto"}

Note: We can use either strings or symbols for property names.


Get all properties as a hash (aka dictionary, map , object, associative array, etc).


The [] operator is used for getting and setting a specific property (just like a plain old Ruby hash).
You can remove a property by setting its value to nil.