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Welcome to Neo4j.rb

Neo4j.rb is a graph database for JRuby.

You can think of Neo4j as a high-performance graph engine with all the features of a mature and robust database. The programmer works with an object-oriented, flexible network structure rather than with strict and static tables — yet enjoys all the benefits of a fully transactional, enterprise-strength database.

It uses two powerful and mature Java libraries:

  • Neo4J - for persistence and traversal of the graph

  • Lucene for querying and indexing.


Why Neo4j.rb or a Graph Database ?

Here are some of the major benefits of Neo4j.rb

  • Domain Modeling - use the language of a graph (nodes/relationship/properties) to express your domain !

    • Schema Less and Efficient storage of Semi Structured Information

    • No O/R mismatch - very natural to map a graph to an Object Oriented language like Ruby.

  • Performance

  • Embedded Database - no database tier, easier to install, test, deploy and configure. It is run in the same process as your application.

  • Express Queries as Traversals

    • Fast deep traversal instead of slow SQL queries that span many table joins.

    • Very natural to express graph related problem with traversals (recommendation engine, find shortest parth etc..)

  • Seamless integration with Ruby on Rails.

  • ACID Transaction with rollbacks support.

Some Examples


Example of creating a Neo4j::Node

require "rubygems"
require 'neo4j' do
  node = (:name => 'andreas')
  node.outgoing(:friends) << (:name => 'peter')
  node.outgoing(:friends).each {|node| puts "name #{node[:name]}"}


Example of mapping a ruby class to a node and delaring properties and relationships and lucene index.

class Person
  include Neo4j::NodeMixin
  property :name
  property :city

  has_n :friends
  has_one :address
  index :name

# assume we have an transaction already running
andreas = (:name => 'andreas')
andreas.friends << (:name => 'peter')
andreas.friends.each {|person| puts "name #{}" }
Person.find("name: andreas") # => 'andreas'


Example of using Neo4j with Rails 3 (ActiveModel)

class User < Neo4j::Model
  attr_accessor :password
  attr_accessible :email, :password, :password_confirmation, :pending_account

  after_save   :encrypt_password

  email_regex = /\A[\w+\-.]+@[a-z\d\-.]+\.[a-z]+\z/i

  property :email
  index :email


  validates :email, :presence => true,:format   => { :with => email_regex }
  validates :email, :uniqueness => true, :unless => :pending_account?
  accepts_nested_attributes_for :avatar, :allow_destroy => true


Generate a Rails Application

Example of creating an Neo4j Application from scratch: (make sure you have installed JRuby version >= 1.6.2)

gem install rails
rails new myapp -m
cd myapp
rails generate scaffold User name:string email:string
rails s
open a webbrowser: http://localhost:3000/users

To run it with Tomcat instead of WEBrick

gem install trinidad

Presentation Materials and other URLs

Project information


Have you found a bug, need help or have a patch ? Just clone neo4j.rb and send me a pull request or email me. Do you need help - send me an email (andreas.ronge at gmail dot com). Please also check/add issues at lighthouse,