Welcome to Neo4j.rb <img src=“https://secure.travis-ci.org/andreasronge/neo4j.png” /> <img src=“https://gemnasium.com/andreasronge/neo4j.png” />¶ ↑

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.

Documentation¶ ↑

• Guides and API

• RDoc

• Blog: Neo4j and Rails 3

• Kvitter Example Application

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¶ ↑

Neo4j::Node¶ ↑

Example of creating a Neo4j::Node

require "rubygems"
require 'neo4j'

Neo4j::Transaction.run do
  node = Neo4j::Node.new (:name => 'andreas')
  node.outgoing(:friends) << Neo4j::Node.new (:name => 'peter')
  node.outgoing(:friends).each {|node| puts "name #{node[:name]}"}
end

Neo4j::NodeMixin¶ ↑

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
end

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

Neo4j::Rails::Model¶ ↑

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

  has_one(:avatar).to(Avator)

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

  ...
end

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 http://andreasronge.github.com/rails3.rb
cd myapp
bundle
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
trinidad

Architecture¶ ↑

As you seen above, neo4j.rb consists of a three layers API:

• Layer 1. For interacting with the basic building blocks of the graph database (node, properties and relationship), see Neo4j::Node and Neo4j::Relationship classes.

• Layer 2. A binding API to Ruby objects, see Neo4j::NodeMixin and Neo4j::RelationshipMixin modules.

• Layer 3. An implementation of the Rails Active Model and a subset of the Active Record API, see Neo4j::Rails::Model class.

Notice that you can always access the lower layers if you want to do some more advanced. You can even access the Java API directly.

Presentation Materials and other URLs¶ ↑

• Presentation: RailsConf 2011

• Nordic Ruby 2010 May 21-23

• Neo4j wiki, check the guidelines and domain modeling gallery pages

Project information¶ ↑

• GitHub

• Issue Tracking

• Twitter

• Mailing list, neo4jrb@googlegroups.com

• Read only, old lighthouse issues

Configuration¶ ↑

Development configuration - You can configure Neo4j through the Neo4j::Config object.

Neo4j::Config[:storage_path] = "/var/neo4j"

Configuring Neo4j from Rails - When using Neo4j.rb from rails you can use the normal rails configuration to set Neo4j configuration.

config.neo4j.storage_path = "#{config.root}/db/neo4j"

Contributing¶ ↑

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).

License¶ ↑

• Neo4j.rb - MIT, see the LICENSE file github.com/andreasronge/neo4j/tree/master/LICENSE.

• Lucene - Apache, see lucene.apache.org/java/docs/features.html

• Neo4j - Dual free software/commercial license, see neo4j.org/