neoid

Neoid

This gem is not stable. There are currently no stable versions. We're working on fixing this right now. Apologies.

Make your ActiveRecords stored and searchable on Neo4j graph database, in order to make fast graph queries that MySQL would crawl while doing them. Originally by @elado.

Neoid is to Neo4j as Sunspot is to Solr. You get the benefits of Neo4j's speed while keeping your schema on your RDBMS.

Neoid does not require JRuby. It's based on the Neography gem which uses Neo4j's REST API.

Neoid offers querying Neo4j for IDs of objects and then fetch them from your RDBMS, or storing all desired data on Neo4j.

Important: If you are hosting your application on Heroku with Neoid, GrapheneDB does support Gremlin code; their add-on is located here. Also be reminded that the Gremlin code is actively being refactored into Cypher.

Changelog

See Changelog. Including some breaking changes (and solutions) from previos versions.

Installation

Add to your Gemfile and run the bundle command to install it.

gem 'neoid'

Requires Ruby 1.9.3 or later and Neo4j 1.9.8.

Installing Neo4j 1.9.8 for your project

We're currently working to bump to 2.1.x land, but for now, you have to use 1.9.8. To get started, install neo4j locally in your project with:

gem install neo4j-core --pre
rake neo4j:install[community,1.9.8]
rake neo4j:start

Usage

Rails app configuration:

Initializer neography and neoid in an initializer that is prefixed with 01_, such as config/initializers/01_neo4j.rb:

ENV["NEO4J_URL"] ||= "http://localhost:7474"

uri = URI.parse(ENV["NEO4J_URL"])

$neo = Neography::Rest.new(uri.to_s)

Neography.configure do |c|
  c.server = uri.host
  c.port = uri.port

  if uri.user && uri.password
    c.authentication = 'basic'
    c.username = uri.user
    c.password = uri.password
  end
end

Neoid.db = $neo

Neoid.configure do |c|
  # should Neoid create sub-reference from the ref node (id#0) to every node-model? default: true
  c.enable_subrefs = true
end

ActiveRecord configuration

Nodes

For nodes, first include the Neoid::Node module in your model:

class User  #
user.neo_node.display_name   # => "elado"

rel = user.likes.first.neo_relationship
rel.start_node  # user.neo_node
rel.end_node    # user.movies.first.neo_node
rel.rel_type    # 'likes'

Disabling auto saving to Neo4j:

If you'd like to save nodes manually rather than after_save, use auto_index: false:

class User  returns a Neography hash

Neoid::Node.from_hash(Neoid.db.get_node_auto_index(Neoid::UNIQUE_ID_KEY, user.neo_unique_id))
# => returns a Neography::Node

Finding all nodes of type

If Subreferences are enabled, you can get the subref node and then get all attached nodes:

Neoid.ref_node.outgoing('users_subref').first.outgoing('users').to_a
# => this, according to Neography, returns an array of Neography::Node so no conversion is needed

Gremlin Example:

These examples query Neo4j using Gremlin for IDs of objects, and then fetches them from ActiveRecord with an in query.

Of course, you can store using the neoidable do |c| c.field ... end all the data you need in Neo4j and avoid querying ActiveRecord.

Most liked movies

gremlin_query =  "Elad"

Neoid.batch(batch_size: 100) do
  User.all.each(&:neo_save)
end.then do |results|
  # results is an array of the script results from neo4j REST.

  results[0].name # => "Elad"
end

Nodes and relationships in the results are automatically converted to Neography::Node and Neography::Relationship, respectively.

With individual then as well as then for the entire batch:

Neoid.batch(batch_size: 30) do |batch|
  (1..90).each do |i|
    (batch << [:create_node, { name: "Hello #{i}" }]).then { |result| puts result.name }
  end
end.then do |results|
  puts results.collect(&:name)
end

When in a batch, neo_save adds gremlin scripts to a batch, instead of running them immediately. The batch flushes whenever the batch_size option is met. So even if you have 20000 users, Neoid will insert/update in smaller batches. Default batch_size is 200.

Inserting records of existing app

If you have an existing database and just want to integrate Neoid, configure the neoidables and run in a rake task or console.

Use batches! It's free, and much faster. Also, you should use includes to incude the relationship edges on relationship entities, so it doesn't query the DB on each relationship.

Neoid.batch do
  [ Like.includes(:user).includes(:movie), OtherRelationshipModel.includes(:from_model).includes(:to_model) ].each { |model| model.all.each(&:neo_save) }

  NodeModel.all.each(&:neo_save)
end

This will loop through all of your relationship records and generate the two edge nodes along with a relationship (eager loading for better performance). The second line is for nodes without relationships.

For large data sets use pagination. Better interface for that in the future.

Behind The Scenes

Whenever the neo_node on nodes or neo_relationship on relationships is called, Neoid checks if there's a corresponding node/relationship in Neo4j (with the auto indexes). If not, it does the following:

For Nodes:

1. Ensures there's a sub reference node (read here about sub references), if that option is on.
2. Creates a node based on the ActiveRecord, with the id attribute and all other attributes from neoidable's field list
3. Creates a relationship between the sub reference node and the newly created node
4. Auto indexes a node in the auto index, for fast lookup in the future

Then, when it needs to find it again, it just seeks the auto index with that ActiveRecord id.

For Relationships:

Like Nodes, it uses an auto index, to look up a relationship by ActiveRecord id

1. With the options passed in the neoidable, it fetches the start_node and end_node
2. Then, it calls neo_node on both, in order to create the Neo4j nodes if they're not created yet, and creates the relationship with the type from the options.
3. Adds the relationship to the relationship index.

Testing

In order to test your app or this gem, you need a running Neo4j database, dedicated to tests.

I use port 7574 for testing.

To run another database locally (read here too):

Copy the entire Neo4j database folder to a different location,

or

symlink bin, lib, plugins, system, copy conf to a single folder, and create an empty data folder.

Then, edit conf/neo4j-server.properties and set the port (org.neo4j.server.webserver.port) from 7474 to 7574 and run the server with bin/neo4j start

Testing Your App with Neoid (RSpec)

In environments/test.rb, add:

ENV["NEO4J_URL"] = 'http://localhost:7574'

In your spec_helper.rb, add the following configurations:

config.before :all do
  Neoid.clean_db(:yes_i_am_sure)
end

config.before :each do
  Neoid.reset_cached_variables
end

Testing This Gem

Run the Neo4j DB on port 7474, and run rake from the gem folder.

Contributing

Please create a new issue if you run into any bugs. Contribute patches via pull requests. Write tests and make sure all tests pass.

TO DO

TO DO

Developed by @elado and @BenMorganIO