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. This JRuby gem uses the mature Neo4j Java library.
It has been tested with Neo4j version 1.8.2 and 1.9.M03 ( see here) and JRuby 1.7.4 (see Travis)
Notice, you do not need to install the Neo4j server since this gem comes included with the database. However, if you still want to use the Neo4j server (e.g. the admin UI) you can connect the embedded databas with the Neo4j server using a Neo4j HA Cluster (see wiki pages).
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RSpecs - There are 2023 RSpecs (478/neo4j-core, 425/neo4j-wrapper and 1120/this gem - 2012 April)
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The Kvitter Rails 3.2x App (kvitter = tweets in Swedish)
Here are some of the major benefits of Neo4j.rb
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Domain Modeling - use the language of a graph (nodes/relationship/properties) to express your domain !
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Schema Less and Efficient storage of Semi Structured Information
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No O/R mismatch - very natural to map a graph to an Object Oriented language like Ruby.
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Embedded Database - no database tier, easier to install, test, deploy and configure. It is run in the same process as your application.
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Express Queries as Traversals
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Fast deep traversal instead of slow SQL queries that span many table joins.
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Very natural to express graph related problem with traversals (recommendation engine, find shortest parth etc..)
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Seamless integration with Ruby on Rails.
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ACID Transaction with rollbacks support.
The neo4j gem depends on the neo4j-wrapper and neo4j-core gems and neo4j-cypher gem.
Neo4j::Rails::HaConsole::Railitie
Neo4j::Rails::Compositions::ClassMethods
Example of using Neo4j with Rails 3 (ActiveModel)
class User < Neo4j::Rails::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 # add an exact lucene index on the email property property :email, :index => :exact 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 u = User.new(:name => 'kalle', :age => 42, :email => "bla@foo.com") u.save
Make sure you are using JRuby !
Example of creating an Neo4j Application from scratch:
gem install rails rails new myapp -m http://andreasronge.github.com/neo4j/rails.rb -O cd myapp bundle rails generate scaffold User name:string email:string rails s open a webbrowser: http://localhost:3000/users
The -O flag above means that it will skip active record. For more information, read the Github Wiki
Example of mapping a ruby class to a node and delaring properties and relationships and lucene index.
class Person
include Neo4j::NodeMixin
property :name, :index => :exact
property :city
has_n :friends
has_one :address
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'
The Neo4j::NodeMixin and Neo4j::RelationshipMixin is implemented in the neo4j-wrapper gem For more information, read the Github Wiki
Neo4j::Node The Java Neo4j Node
Neo4j::Relationship The Java Relationship
Neo4j The Database
Neo4j::Cypher Cypher DSL, see RSpec spec/neo4j/cypher_spec
Neo4j::Algo Included algorithms, like shortest path
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
The Neo4j::Node and Neo4j::Relationship is implemented in the neo4j-core gem.
For more information, read the Github Wiki
Yes, check Neo4j.rb Ha Cluster or Screencast Notice, you don’t need to install the Neo4j Server, but it could be a useful tool to visualize the graph.
As you seen above, neo4j.rb consists of a three layers API:
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Layer 1, neo4j-core. For interacting with the basic building blocks of the graph database (node, properties and relationship), see Neo4j::Node and Neo4j::Relationship classes.
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Layer 2, neo4j-wrapper. A binding API to Ruby objects, see Neo4j::NodeMixin and Neo4j::RelationshipMixin modules.
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Layer 3, neo4j. An implementation of the Rails Active Model and a subset of the Active Record API, see Neo4j::RailsNode and Neo4j::RailsRelationship 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.
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"
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).
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Neo4j.rb - MIT, see the LICENSE file github.com/andreasronge/neo4j/tree/master/LICENSE.
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Lucene - Apache, see lucene.apache.org/java/docs/features.html
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Neo4j - Dual free software/commercial license, see neo4j.org/
Notice there are different license for the neo4j-community, neo4j-advanced and neo4j-enterprise jar gems. Only the neo4j-community gem is by default required.