Introduction to MongoDB, Rails Mongoid ORM and some data modelling examples.

1. Simple MongoDB design for
Web (Rails) apps
Sérgio Santos
@sdsantos
Improve Coimbra

2. Introduction / Disclamer

3. Bundlr MongoDB stats
MongoDB from the start
~ 3½ years of development
~ 6 GB of data
~ 6 million documents
Cloud hosted on MongoHQ

4. Burocracia MongoDB stats
~ 3 weekends of development
~ 300MB of data
~ 721 documents
~ 400KB per document
Cloud hosted on MongoLab

5. Why MongoDB?

6. MongoDB 101

7. Documents

8. Collections

9. References

10. Embeds

11. Rails MongoDB ORMs

12. Mongoid vs MongoMapper

13. Mongoid

14. Models
class Person
include Mongoid::Document
end
person = Person.new
person[:name] = 'Sérgio'
person[:age] = 26
person.save

15. Models
class Person
include Mongoid::Document
field :name, type: String
field :age, type: Integer
end
person = Person.new
person.name = 'Sérgio'
person.age = 26
person.save

16. Persistence
person = Person.create(name: 'Sérgio', age: 26)
person.update_attributes(name: 'Sérgio Santos')
person.touch
person.delete
person.destroy
person.rename(:name, :first_name)

17. Querying
person = Person.find("4baa56f1230048567300485c")
people = Person.where(age: 18)
people = Person.where(name: 'Sérgio').not(age: 26)
Person.count
Person.all.avg(:age)
-- INSERT MAP/REDUCE CLEVER EXAMPLE HERE --

18. References
class Band
include Mongoid::Document
has_many :members
end
class Member
include Mongoid::Document
field :name, type: String
belongs_to :band
end

19. References
# The parent band document.
{
"_id" : ObjectId("4d3ed089fb60ab534684b7e9")
}
# The child member document.
{
"_id" : ObjectId("4d3ed089fb60ab534684b7f1"),
"name" : "Matt Berninger"
"band_id" : ObjectId("4d3ed089fb60ab534684b7e9")
}

20. Embeds
class Band
include Mongoid::Document
embeds_many :albums
end
class Album
include Mongoid::Document
field :name, type: String
embedded_in :band
end

21. Embeds
{
"_id" : ObjectId("4d3ed089fb60ab534684b7e9"),
"albums" : [
{
"_id" : ObjectId("4d3ed089fb60ab534684b7e0"),
"name" : "Boxer",
}
]
}

22. Extras
timestamps
identity map & cache
paranoia
versioning

23. Cloud Hosting

25. The Nice Stuff

26. No need to create the
collection
class Band
include Mongoid::Document
end

27. Store anything
class ParamsStore
include Mongoid::Document
end
class ApplicationController < ActionController::Base
before_filter do
Stuff.create(params)
end
end

28. Store long stuff
class Website
include Mongoid::Document
field :html, type: String
field :css, type: String
field :javascript, type: String
embeds_many :images
end
class Image
include Mongoid::Document
field :size, type: Integer
field :file, type: Moped::BSON::Binary
embedded_in :website
end

29. Geo
class Person
include Mongoid::Document
field :location, :type => Array
index(
{ location: Mongo::GEO2D },
{ min: -180, max: 180 }
)
end
coimbra_location = [20, -8]
Person.geo_near(coimbra_location).spherical

30. Full text search
class Document
include Mongoid::Document
field :content, :type => String
index(
{:content => 'text'},
{:default_language => 'portuguese’}
)
end
Document.text_search('IKEA')

31. Caveats (not so nice)
No joins
Impact of key length
No integrity checks for references
Document size limit of 16MB
Nesting depth limit of 100

32. ( Bundlr ) Examples

33. Settings
class User
include Mongoid::Document
embeds_one :settings
end
class Settings
include Mongoid:Document
field :receive_emails, type: Boolean
field :theme, type: Symbol
embedded_in :user
end

34. Oauths
class User
include Mongoid::Document
embeds_many :oauths
index [["oauths.provider", Mongo::ASCENDING],
["oauths.uid", Mongo::ASCENDING]]
end
class Oauth
include Mongoid:Document
field :provider, type: String
field :token, type: String
field :secret, type: String
field :uid, type: String
embedded_in :user
end

35. Activity Stream
class Activity
include Mongoid::Document
include Mongoid::Timestamps
field :verb, :type => Symbol
field :actor, :type => Hash
field :object, :type => Hash
field :target, :type => Hash
field :receivers, :type => Array
embeds_many :likes
end

36. Relationships
class User
include Mongoid::Document
has_and_belongs_to_many :followers, :class_name => "User",
:inverse_of => :followed_users
end
{
_id: ObjectId("4d541f6823380f670d000008"),
follower_ids: [
ObjectId("4d4ea8ec86d56d2907000003"),
ObjectId("50fe17c226c1b7000200018a")
],
}
Need smarter relationships? Embed them!

37. Other examples
Model hierarchy
Migrations
Changing schema?
No right way of doing things… is all about context!

38. Wrapping up…

39. Sérgio Santos
@sdsantos
me@sergiosantos.info
Simple MongoDB design for
Web (Rails) apps
Improve Coimbra