MongoDB & Mongoid with Rails

MongoDB
{ name: “mongo”, type: “db” }

“MongoDB is designed to be
human-oriented.
It reduces the burden of
programming.
It tries to push jobs back to
machines. You can accomplish more
tasks with less work, in smaller yet
readable code.” - Banker

built for speed
document/collection oriented
dynamic queries and indexes
replication and failover

websites from yesterday and today
high volume traffic
high scalability
storage of objects and JSON

MongoDB with Ruby
because we all want ActiveRecord...

mongo-ruby-driver
mongomapper
mongoid

Spiff uses Mongoid

class Post
include Mongoid::Document
field :title, :type => String
field :body, :type => String
end

@posts = @db.collection('posts')
@document = {:title => "MongoDB on Rails",
:body => "Revelatory! Loved it!"}
@posts.save(@document)

Associations in Mongoid

class Post
has_many :comments
end

class Comment
field :rant, :type => String
belongs_to :post, :inverse_of => :comments
end

This creates an Embedded Document.

@posts = @db.collection('posts')
@document = {:title => "MongoDB on Rails",
:body => "Revelatory! Loved it!",
:comments => [{:rant => “I completely disagree”}]
}
@posts.save(@document)

Keys, Validations, Timestamps & Hooks
class Post
include Mongoid::Timestamps

field :slug, :type => String
has_many :comments

has_key :title, :unique => true # “Audi IMS” becomes “audiims”

validates_presence_of :title, :body
validates_unqiueness_of :title

before_save :set_slug

def set_slug

self.slug = “#{title.parameterize}-#{body[0..3]}”
end
end

Versioning a Mongo Document
class Post
include Mongoid::Versioning

has_many :comments

has_key :title, :unique => true # “Audi IMS” becomes “audiims”

validates_presence_of :title, :body
validates_unqiueness_of :title

before_save :set_slug

def set_slug

self.slug = “#{title.parameterize}-#{body[0..3]}”
end
end

Access related items
class Post
include Mongoid::Versioning

has_many :comments

belongs_to_related :account
has_many_related :sources

.....
end

database.yml meet database.mongo.yml

But does it blend?

Post.all(:conditions => { :title => “Rails 2.3” })
Post.find(:all, ...)
Post.first(...)

Post.find_or_create_by(:title => “Merb is dead”)
Post.find_or_initialize_by(...)

Associations:
@post.comments.all

fuck SQL! Criteria is the shit.

Criteria#all - perform exact matches

Post.criteria.all(:title => [ “Rails”, “2.3” ])

Criteria#find - match key/value
Post.criteria.and(:created_at.gt => 2.months.ago)

Criteria#exclude
Post.criteria.exclude(:created_at => Date.today)

Criteria#id - match document id

Post.criteria.id(“4b2fe28ee2dc9b5f7b000029”)

Criteria#in - match any of the values in an array

Post.criteria.in(:title => [“Merb”, “Rails”, “Ruby”]

Criteria#order_by
Post.criteria.order_by([[:created_at, :desc], [:title, :asc] ])

Criteria also has #limit, #not_in, #only, #skip

arithmetic, grouping & aggregation
#max, #min, #sum, #aggregate, #group

“But what about named scopes dude?!” -Gabe

named_scope :active, criteria.where(:active => true) do
def count
size
end
end

named_scope :inactive, :where => { :active => false }

named_scope :frags_over, lambda { |count| { :where => { :frags.gt => count } } }

named_scope :deaths_under, lambda { |count| criteria.where(:deaths.lt => count) }

You can chain any of the Criteria API
Post.in(:title => [“Rails”, “Ruby”]).where(:created_at.gt => 2.months.ago).skip(10)

class Post

class << self
def ruby_related
criteria.in(:title => [“Ruby”, “Rails”])
end

def in_last_two_months
criteria.where(:created_at.gt => 2.months.ago))
end
end
end

Post.ruby_related.in_last_two_months

additional mongoid features
Composite Keys
Indexing
Inheritance
native MongoDB expressions

MongoDB & Mongoid with Rails

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