Shutl mongob usergroup talk jan 2013

MongoDB and Ruby

domain modeling with MongoMapper

Wednesday, 23 January 13

Volker Pacher
senior developer @shutl
@vpacher
http://github.com/vpacher


• SaaS platform


• SaaS platform
• we provide an API for carriers and merchants


• SaaS platform
• customers can chose between a delivery either:


• SaaS platform
within 90 minutes of purchase


• SaaS platform
or a 1 hour window of their choice


• SaaS platform
(same day or any day)


• SaaS platform
• fastest delivery to date 14:00 min


• SaaS platform
• customers: Argos, Maplins, DrEd.com ...


• SaaS platform
• json api


• SaaS platform
• json api
•built with sinatra, jruby, neo4j and mongodb

Shutl Main Red: Shutl Accent Red:
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Let’s get going:
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red on lighter tones

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Please note:
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appear on in any ‘dark’ colour
background.

5 Branding Guidelines



Let’s get going:
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• install mongodb with brew install mongodb
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• in your gemﬁle:
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• gem ‘mongo’



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• gem ‘mongo’
• gem ‘bson’



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background.


• gem ‘mongo’
• gem ‘bson’
• gem ‘bson_ext’



Let’s get going:
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Please note:

background.


• gem ‘mongo’
• gem ‘bson’
• gem ‘bson_ext’

• run bundle install


MongoMapper


MongoMapper

• http://mongomapper.com/


MongoMapper

• written by John Nunemaker (github)


MongoMapper

• written by John Nunemaker (github)
• code at https://github.com/jnunemaker/
mongomapper


Alternatives:


Alternatives:

• Mongoid: http://mongoid.org/en/mongoid/index.html


Alternatives:

• MongoODM: https://github.com/carlosparamio/mongo_odm


Alternatives:

• MongoODM: https://github.com/carlosparamio/mongo_odm
• MongoModel: http://www.mongomodel.org/


installation:


installation:

• gem ‘mongo_mapper’


installation:

• gem ‘mongo_mapper’
• run bundle install


db initialization:

include MongoMapper

MongoMapper.connection =
Mongo::Connection.new('localhost', 27017)
MongoMapper.database = ‘development’

MongoMapper.database.authenticate('username','password')


First document:

class User
include MongoMapper::Document

key :name, String, required: true
key :age, Integer

one :address
many :notes

timestamps!
end


embedded document:

class Note
include MongoMapper::EmbeddedDocument

key :text, String
end


create a document:
user = User.new(name:'James Chester')
user.notes.build(text:'a note')

user.save!

User.where(:name => 'James Chester').first


What is an embedded document?



• a document has it’s own collection in the database (table)



• an embedded document can only reside inside a document
or another embedded document



• the alternative in sql without join table would be to serialize



• the alternative in sql without join table would be to serialize
• in MongoDB it is possible to query inside embedded
documents and structures and also to index inside them


When to use embedded and when not to



• only embed when the document will be shown in the
context of the parent document



• if you need to access to the documents on it’s own use
associations (i.e. all notes)



• if you need to access to the documents on it’s own use
associations (i.e. all notes)
• they work the same way but declare a normal document
instead of an embedded one


{
id: '50fd8a786bcb608e1c000002',
name: 'James Chester',
address: {},
notes:
[
{ id: '50fd8b246bcb608e1c000003', text: 'a note'}
]
}


types:


types:

• mongomapper supports the ruby data types:
Integer, Float, String, Array, Hash, Object, Time, NilClass


types:

• additionally mongomapper adds support for:
Binary, Boolean, Date, ObjectId and Set


types:

• additionally mongomapper adds support for:
Binary, Boolean, Date, ObjectId and Set
• ability to add custom types


custom types:

class UpcaseString
def self.to_mongo(value)
value.nil? ? nil : value.to_s.upcase
end

def self.from_mongo(value)
to_mongo(value)
end
end


ﬁnding a document:



• ﬁnd by id: User.find(‘50fd8a726bcb608e1c000001’)



• ﬁnd by ﬁeld: User.first(:name => 'James')



• query inside embedded document or structure (Hash)
User.all(‘address.postcode’ => 'EC2A 4HJ')



• query inside embedded document or structure (Hash)
User.all(‘address.postcode’ => 'EC2A 4HJ')

• finders are:
.find, .all, .first, .last, .paginate


dynamic querying:


dynamic querying:

• MongoMapper uses plucky to the allow the construction of query
proxy objects that only get executed when needed


dynamic querying:

• https://github.com/jnunemaker/plucky


dynamic querying:

• User.where(:created_at.gte => 3.days.ago).sort(:created.desc)


dynamic querying:

• User.where(:created_at.gte => 3.days.ago).sort(:created.desc)
• .where, .count, .field, .sort/.order, .limit,
.skip, .offset


operators:


operators:

• all mongodb operators can be used directly in mongomapper


operators:

• http://docs.mongodb.org/manual/reference/operators/


operators:

• User.where(:age => {:$gt => 20, :$lt => 45})


operators:

• or shorthand:


operators:

• or shorthand:
• User.where(:age.gt => 25)


destroy/delete:


destroy/delete:

• destroy triggers callbacks, delete does not


destroy/delete:

• User.destroy(‘50fd8a786bcb608e1c000002’)


destroy/delete:

• User.destroy_all


destroy/delete:

• User.destroy_all
• User.destroy_all(:age.gt => 25)


validations:

MongoMapper uses Rails ActiveModel:Validations

http://api.rubyonrails.org/classes/ActiveModel/Validations.html


include MongoMapper::Document

key :name, String, required: true
key :age, Integer

validates_numericality_of :age

validates :age_larger_18

def age_larger_18
errors.add( :age, "too young") if age < 18
end
end


shorthands available:

:required – Boolean
:unique – Boolean
:numeric – Boolean
:format – Regexp
:in – Array
:not_in – Array
:length – Integer, Range, or Hash


indexes:


indexes: • put indexes into the initializer


• index on single ﬁeld:
User.ensure_index(:name)



• index multiple keys:
User.ensure_index([[:name, 1], [:age, -1]])




• the order of keys is important in
compound indexes




compound indexes
• unique index:
User.ensure_index [[:name, 1]], :unique => true




compound indexes
• unique index:
User.ensure_index [[:name, 1]], :unique => true

• delete index:

User.drop_index(:name)


using the decorator/presenter pattern for schemaless dbs

decorator

‘decorates’ object for presentation

controller

passes decorated object to view

retrieves object
view

mongo
DB


Any questions?

Volker Pacher

volker@shutl.co.uk shutl.co.uk
@vpacher @shutl

Shutl mongob usergroup talk jan 2013

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