Simple MongoDB design for Rails apps

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

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

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

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

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

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)

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 --

References
class Band
has_many :members
end
class Member
belongs_to :band
end

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

Embeds
class Band
embeds_many :albums
end
class Album
embedded_in :band
end

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

Extras
timestamps
identity map & cache
paranoia
versioning

Simple MongoDB design for Rails apps

No need to create the
collection
class Band
end

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

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

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

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

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

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

Oauths
class User
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

Activity Stream
class Activity
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

Relationships
class User
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!

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

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

Simple MongoDB design for Rails apps

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Editor's Notes