Leveraging relations at scale with Neo4j

alberto@graphenedb.com | @albertoperdomo
Leveraging relations at
scale with Neo4j
Madrid.rb - July 2013
Alberto Perdomo
GrapheneDB

About me
๏Co-founder of Aentos
๏Ruby developer
๏GrapheneDB: Neo4j as a Service

Origin of Graphs

Leonhard Euler, 1736

Königsberg Bridge
Problem

Euler’s Technique

Königsberg Problem
Graph

The Math
G=( V, E )

Types of Graphs

Undirected Graph
A
B
C
Adam
Michael
John
Example: Facebook Friendships

Directed Graph
A
B
C
Adam
Michael
John
Example: Twitter follows

Weighted Graph
A
B
C
0.6 0.8
Adam John
Star Wars: Episode IV
Example: Movie Ratings

Labeled Graph
A C
friend_of fan_of
Adam LA Lakers
Michael
fan_pagefriend_of
B
user
user
Example: Facebook friendships
+ fan pages

Property Graph
A
B
C
rated: 0.6
directed
Type: Cast Member
Name: George Lucas
Born_At: 1944-05-14
Type: Movie
Title: Star Wars Episode IV - A New Hope
Release: 1977
Type: User
Name: Adam
Age: 34
Country: USA
wrote
Example: IMDB

Graph Databases

Graph DB: Deﬁnition
๏Uses graph as primary data structure
๏Property graph: store data as nodes,
relations and properties

Graph DBs
vs
other DBs

A graph can be modeled
with almost any technology

Mysql vs Neo4j
๏1M users
๏Friends of friends for 1K users
Depth Execution Time – MySQL Execution Time – Neo4j
2 0. 016 0. 010
3 30. 267 168
4 1, 543. 505 1. 359
5 Not Finished in 1 Hour 2. 132
http://www.neotechnology.com/how-much-faster-is-a-graph-database-really/,
http://www.manning.com/partner/

Conventional DBs
๏Index lookup to ﬁnd out adjacent nodes
๏Depends on total number of vertices
and edges in DB (global)

Graph DB: Deﬁnition
๏Any system that provides index-free
adjacency[1]
๏Linear cost to retrieve adjacent nodes:
depends on the number of local neighbours
[1] http://www.slideshare.net/slidarko/problemsolving-using-graph-traversals-searching-scoring-ranking-and-recommendation

While DB grows, cost of
local step remains the same

Modeling connected
data is natural

When use a graph?

High density of
relations

A search engine for
relations

Graph analysis
๏Recommend vertices to user x
๏Search for y given x
๏Score x given its local neighbourhood
๏Rank x relative to y

Recommendations

Social Graph
A representation of the
relationship between people and
other people

Social Graph
๏Facebook
๏Twitter
๏LinkedIn
“Since you have
many friends in
common, you might
know fellow X.”

Interest Graph
A representation of the
relationship between people
and things

Interest Graph
๏Pinterest
๏Instagram
๏Quora
๏Spotify
“A lot of people who
like x like you, also
like y, too.”

Pinterest Interest Graph
http://engineering.pinterest.com/post/55272557617/building-a-follower-model-from-scratch

e-commerce

e-commerce
Upselling

Recommendations
bought
Many users
Star Wars I DVD
bought
C
A
B
looking at
A user
Star Wars Trilogy
DVD Pack
“Customers who bought a, also bought b”

Rank x
๏Rank nodes based on their
neighbourhood/network
๏Klout, PageRank

Geospatial problems
๏Travelling Salesman
๏Route for delivery of parcels
๏Optimize route for duration, distance,
trafﬁc ﬂow, etc.
๏Must not be physical path, example:
connecting people

Recognize patterns
๏Fraud detection
๏Debt compensation systems
๏Text analysis
๏Chain of exchanges

Visualize connected
data

Your domain model
determines what you
can do

High chances your
data is a graph

The Neo4j
Graph Database

Data modeling

White board

Then Add Complexity

Process, Tips
๏Model facts as nodes
๏Use relations to model relations
between facts
๏Refactor - schema-less !

Neo4j
๏Graph DB written in Java
๏Java API + HTTP/REST + Embedded
๏Full ACID
๏Built-in indexing (or roll your own)
๏Scale: 32B nodes, 32B relations

The Cypher Query
Language

Cypher
๏Neo4j’s graph query language
๏Declarative pattern matching
๏“SQL for graphs”
๏ASCII art

Pattern matching

Basic Syntax
A B
(a) --> (b)

Basic Syntax
START a=node(*)
MATCH (a)-->(b)
RETURN a,b;

(a) --> (b)

Relations
(a) -[:ACTED_IN]-> (b)
A B
ACTED IN

Syntax
START a=node(*)
MATCH (a)-[:ACTED_IN]->(b)
RETURN a.name, b.title;

Syntax
START a=node(*)
MATCH (a)-[r:ACTED_IN]->(b)
RETURN a.name, r.roles, b.title;

Syntax
(a) --> (b) <-- (c)
A B C

Syntax
START a=node(*)
MATCH (a) -[:ACTED_IN]->(m)<-[:DIRECTED]- (d)
RETURN a.name, m.title, d.name;

Sort & Limit
START a=node(*)
MATCH (a) -[:ACTED_IN]->(m)<-[:DIRECTED]- (d)
RETURN a.name, m.title, d.name
ORDER BY(count) DESC
LIMIT 5;

Starting point: All nodes
START n=node(*)
RETURN n;

Starting point: Where
START n=node(*)
WHERE has (n.name) AND n.name = “George Lucas”
RETURN n;

Starting point: Auto
Index
START n=node:node_auto_index(name=“George Lucas”)
RETURN n;

Starting point: multiple
nodes
START lucas=node:node_auto_index(name=“George Lucas”),
ford=node:node_auto_index(name=”Harrison Ford”)
MATCH (lucas) -[:DIRECTED]-> (m) <-[:ACTED_IN]- (ford)
RETURN m.title;

Multiple relations
MATCH (a)-[:ACTED_IN|DIRECTED]->()

Constraints with
comparison
START a=node:node_auto_index(name=“Alberto Perdomo”)
MATCH (a) -[:KNOWS]-> (b)
WHERE b.born < a.born
RETURN a.name;

Contraints with
patterns
MATCH (alberto)-[:KNOWS*2]->(fof)
WHERE NOT((ferblape)-[:KNOWS]-(fof))

Variable length paths
MATCH (alberto)-[:KNOWS*2]->(fof)

Agreggation
๏count(x)
๏min(x)
๏max(x)
๏avg(x)
๏collect(x)
๏ﬁlter(x)

Updating the graph
๏Create, Set, Delete nodes
๏Create, Set, Delete relations

Neo4j: More features

Built-in Graph Algos
๏shortest path
๏allSimplePaths
๏allPaths
๏dijkstra

Extending Neo4j: Plugins
๏Provides extra API endpoints to run
external code. JAR ﬁles.
๏Neo4j-Spatial
๏Neo4j-Sparql

Neo4j from Ruby
๏ Neography
๏ Wrapper around REST API
๏ Neo4j.rb:
๏ Language binding for JRuby
๏ ActiveModel, Mixins
๏ Embedded Neo4j w/ GPL license (not only?)
๏ Other?

Neography
# Node creation:
node1 = @neo.create_node("age" => 31, "name" => "Max")
node2 = @neo.create_node("age" => 33, "name" => "Roel")
# Node properties:
@neo.set_node_properties(node1, {"weight" => 200})
# Relationships between nodes:
@neo.create_relationship("coding_buddies", node1, node2)
# Get node relationships:
@neo.get_node_relationships(node2, "in",
"coding_buddies")
# Use indexes:
@neo.add_node_to_index("people", "name", "max", node1)
@neo.get_node_index("people", "name", "max")
# Cypher queries:
@neo.execute_query("start n=node(0) return n")

Neo4j.rb ActiveModel
class User < Neo4j::Rails::Model
attr_accessor :password
attr_accessible :email, :password, :password_confirmation
after_save :encrypt_password
email_regex = /A[w+-.]+@[a-zd-.]+.[a-z]+z/i
# add an exact lucene index on the email property
property :email, index: :exact
has_one(:avatar).to(Avator)
accepts_nested_attributes_for :avatar, allow_destroy: true
end

Neo4j.rb Mixin
class Person
include Neo4j::NodeMixin
property :name, index: :exact
property :city
has_n :friends
has_one :address
end

Neo4j Licensing
๏ Community: GPL
๏ Advanced: Commercial + AGPL
๏ Monitoring
๏ Support
๏ Enterprise: Commercial + AGPL
๏ Monitoring + HA clustering + Online backups
๏ Support

Getting Started
๏www.neo4j.org/learn/try
๏www.neo4j.org/download
๏download -> unpack -> start
๏http://localhost:7474

Built in Web Admin
๏Stats
๏Console & browser
๏Indexes

Neo4j Resources
๏ Code & Issues: github.com/neo4j/neo4j
๏ Resources: www.neo4j.org/learn
๏ Mailing List: groups.google.com/forum/#!forum/neo4j
๏ Questions: stackoverﬂow.com/questions/tagged/neo4j
๏ Meetups: www.neo4j.org/participate/events/meetups
Free download:
http://graphdatabases.com/

GrapheneDB:
Neo4j as a Service

@albertoperdomo
alberto@graphenedb.com
Thanks!

Leveraging relations at scale with Neo4j

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