OrientDB document or graph? Select the right model (old presentation)

Document rev 1.1

Select the right model

„Document vs Graph,
what is the answer?“
© Luca Garulli - 2012 Licensed under a Creative Commons Attribution-NoDerivs 3.0 Unported License Page 1

OrientDB supports multiple models

Document
Graph
Custom Graph*

*available in 1.2


What is the best choice for my domain?


Facts
Graph Model has been built on top of
the Document Model

But why it is so fast?
Because in OrientDB relationships are
direct links, not relational JOINs

This is the reason why
even using the Document model
you can manage complex graphs
of objects


Relationships


Graph Model
Vertex & Edges I

in
Vertex Vertex
A B
out

Connections using
bidirectional Edges


Graph Model
Vertex & Edges II

in
Vertex Vertex
Edge A-B
A B
out

Edges in OrientDB are records
with own RecordID of class
«OGraphEdge» or just «E» as
alias.


Graph Model
Vertex & Edges III

out* in
Vertex Vertex
Edge A-B
A B
out * in

To access to the ougoing vertices use «out.in» because:

1. Vertex A exits through «out» to go to the
2. Edge, and then
3. «in» to arrive to the Vertex B


Graph Model
summary

connect vertices using edges

A vertex has "in" for the incoming
relationships and "out" for the outgoing
relationships

are always bidirectional


Document Model
oneway direct connections

students *
Professor Student
Jay Steve

Connections are
directed without using
Edges and are always
monodirectional


Document Model
express the cardinality

students *
Professor Student
Jay Steve

Students = N
Using LINKSET type city 1

City
Palo Alto
City = 1
Using LINK type


Document Model
express the cardinality

students *
Professor Student
Jay Steve

Use LINKSET or LINKMAP for
unordered collection doesn’t
accept duplicates, otherwise
LINKLIST as ordered with
duplicated


Document Model
bidirectional connections
students *

Professor Student
Jay Steve

professors *

To create bidirectional links create
2 relationships:
1. from Professor to Student
2. from Student to Professor


Document Model
summary

Connections are always as oneway, to have a
bidirectional relationship create 2 connections

Single cardinality: LINK

Multiple cardinality:
LINKSET and LINKMAP for unordered, no duplicates
and LINKLIST: ordered allows duplicates


Graph Model
vs
Document Model


Graph Model
PROS
1. Ability to use GREMLIN and full TinkerPop
Blueprints stack

2. Connections are always bidirectional: leave open
the ability to move in all the directions even is
not planned at the beginning

3. Edges can have properties


Graph Model
CONS
1. Edges are record themselves, so db is bigger: one
record more per edge

2. Traversing between Vertices needs to load the
Edge record too, so it‘s slower

3. All the outgoing relationships are inside the "out"
collection: worst performance in case you have
connections of different kind

Document Model
PROS
1. Lighter than Graph Model, no need for a separate
record to manage relationships

2. Faster on traversing because links are directing
bypassing the Edge records

3. Finer grained cardinality setting also the
relationship type


Document Model
CONS
1. Cannot use the GREMLIN and full TinkerPop
Blueprints stack

2. No native bidirectional connection, so the
application has to manage the double connection

3. Edges cannot have properties


Suggestions
What to use?

Graph and Document models have PROS
and CONS. Often it‘s hard to select the
right one because there couldn‘t be a
right one.

The next use cases are very generics so
don‘t take them as rule of the thumb

Suggestions
(1) Social Applications

Highly suggested the Graph Model because
you‘re always ready to analyze the graph in
any direction using advanced tools like
GREMLIN language.

Graph algorithm already developed through
TinkerPop stack like Shortest Path, Ranking,
etc.

Suggestions
(2) CRM/Business Applications

You could select both. Here the Document
Model is a good candidate because
relationships don‘t change so often and are
mostly known at the beginning


Suggestions
(3) Highest performance

Since the Graph Model is heavier because
requires more records and more traverse
time, the suggested here is the
Document Model


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Luca Garulli
Author of CEO at

Document-Graph NoSQL
Open Source project
Ltd, London UK

www.twitter.com/lgarulli

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