Neo4j and Ruby

Hello my name is

Brian Underwood
Developer Advocate at Neo Technology
Ruby lover, data enthusiast
@ cheerfulstoic | brian@brian-underwood.codes
Grand Adventures and Household Chores

Neo4j is a Graph Database

Graph	Chart

Why Neo4j?

Expressive and natural data modeling
Easy and powerful query language (Cypher)
Fast and easy querying on complex data relationships
ACID / Replication

Neo4j Crash Course

Nodes and Relationships
Both are key→value stores
Nodes can have zero or more labels (User, Post, etc…)
Relationships have a type (i.e. wrote_post)

Neo4j Crash Course

Relationships go from one node to another (directional)
Querying can be directional or direction agnostic

Neo4j Crash Course

Cypher

MATCH (user:User)<-[rel:written_by]-(post:Post)
  WHERE user.id = 123
  RETURN rel.location, post

Return post and location it was made
Location stored on the relationship

Cypher

MATCH (u:User)<-[:written_by]-(:Post)<-[:comments_on]-(c:Comment)-[:written_by]->(u2:User)
  WHERE u.id = 123
  RETURN u2.name, count(c)

Returns users who commented on posts by user #123
Gives count of the number of comments for each users

Neo4j Resources

http://graphdatabases.com O’Reilly’s Graph Databases (free and a great intro to the internals of Neo4j)
http://neo4j.com/developer/ruby/ Neo4j Ruby guides
http://neo4j.com/developer/cypher/ Cypher Introduction

Why should Rubyists use Neo4j?

Natural and agile data modeling
Higher level abstraction
Web console like ruby console
Great support

What is the Neo4j gem?

An ActiveModel compliant Ruby wrapper for the Neo4j graph database.

Neo4j gem features

OGM (Object Graph Model)
- Properties
- Indexes / Constraints
- Callbacks
- Validations
- Assocations

Neo4j gem features

Modeling nodes and relationships
Query building / chaining interface similar to arel
Transactions
Migrations (for data)

Points of Pride

Well tested

Points of Pride

Well documented

Points of Pride

Actively supported

Points of Pride

Actively supported

Points of Pride

Well loved

Points of Pride

Won an award!

Models

class Post
  include Neo4j::ActiveNode

  property :subject
  property :text

  has_one :out, :author, type: :WRITTEN_BY, model_class: :User, rel_class: :WrittenBy
  has_many :out, :tags, type: :TAGGED_AS  # model_class :Tag is assumed
end

class WrittenBy
  include Neo4j::ActiveRel

  from_class :Post
  to_class   :User
  type :WRITTEN_BY # Not needed as default is based on model name

  property :location
end

Usage

class Post
  has_one :out, :author, type: :WRITTEN_BY, model_class: User
  has_many :in, :comments, type: :COMMENTS_ON
end

class Comment
  has_one :out, :author, type: :WRITTEN_BY, model_class: :User
end

class User
  has_many :in, :posts, origin: :author
end

user.posts.comments(:c).author(:u2).pluck('u2.name, count(c)')

# Compare to:
# MATCH (u:User)<-[:written_by]-(:Post)<-[:comments_on]-(c:Comment)-[:written_by]->(u2:User)
#   WHERE u.id = 123
#   RETURN u2.name, count(c)

A deeper example

class Post
  has_many :in, :categories, type: :COMMENTS_ON
end

class Comment
  has_one :out, :post, type: :COMMENTS_ON
  has_one :out, :author, type: :WRITTEN_BY, model_class: :User
end

class Category
  property :name, constraint: :unique
end

def post_category_counts(comments)
  comments.post(:post).categories(:category).pluck('category.name', 'count(post)')
end

A deeper example

class Comment
  def self.post_category_counts
    all.post(:post).categories(:category).pluck('category.name', 'count(post)')
  end
end

A deeper example

> Comment.where(body: /.*mountains.*/i).post_category_counts

 Comment#post#categories 3ms
  MATCH (result_comment:`Comment`)
  WHERE (result_comment.body =~ {result_comment_body})
  MATCH (result_comment)-[rel1:`COMMENTS_ON`]->(post:`Post`)
  MATCH (post)<-[rel2:`COMMENTS_ON`]-(category:`Category`)
  RETURN
    category.name,
    count(post) | {:result_comment_body=>"(?i).*mountains.*"}

A deeper example

> Comment.all.branch { author.where(age: (20..30)) }.post_category_counts

 Comment#post#categories 6ms
  MATCH (n:`Comment`)
  MATCH (n)-[rel1:`WRITTEN_BY`]->(result_author:`User`)
  WHERE (result_author.age IN RANGE({result_author_age_range_min}, {result_author_age_range_max}))
  MATCH (n)-[rel3:`COMMENTS_ON`]->(post:`Post`)
  MATCH (post)<-[rel4:`COMMENTS_ON`]-(category:`Category`)
  RETURN
    category.name,
    count(post) | {:result_author_age_range_min=>20, :result_author_age_range_max=>30}

Some supported gems

devise
will_paginate
paperclip
searchkick
factory_girl

Projects built with neo4j gem (libraries)

Projects built with neo4j gem (applications)

Neo4j.rb resources

Neo4j.rb resources (videos)

Short screencast series

Demo time!

Code available on: https://github.com/neo4j-examples/ruby_code_analytics

Example on Heroku: https://ruby-neo4j-code-analysis.herokuapp.com/

Uses:

Ruby’s TracePoint library to trace the execution of Ruby code
The parser gem to parse the AST of files where code was executed

Demo time!

Thank you! My info again:

Brian Underwood

Developer Advocate at Neo Technology

@ cheerfulstoic | brian@brian-underwood.codes

My wife’s travel blog:

Grand Adventures and Household Chores

Neo4j and Ruby

Hello my name is

Neo4j is a Graph Database

Why Neo4j?

Neo4j Crash Course

Neo4j Crash Course

Neo4j Crash Course

Cypher

Cypher

Neo4j Resources

Why should Rubyists use Neo4j?

What is the Neo4j gem?

Neo4j gem features

Neo4j gem features

Points of Pride

Well tested

Points of Pride

Well documented

Points of Pride

Actively supported

Points of Pride

Actively supported

Active on StackOverflow

Gitter chat room

Twitter

Points of Pride

Well loved

Points of Pride

Won an award!

Models

Usage

A deeper example

A deeper example

A deeper example

A deeper example

Some supported gems

Projects built with neo4j gem (libraries)

Projects built with neo4j gem (applications)

Projects built with neo4j gem (applications)

Neo4j.rb resources

Neo4j.rb resources (videos)

Demo time!

Demo time!

Thank you! My info again:

Status of the presentation