Brown bag presentation on using MongoDB and Mongoid with Rails.

1. MongoDB
{ name: “mongo”, type: “db” }

2. “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

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

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

5. caveats

6. no transactions

7. relationships

8. MongoDB with Ruby
because we all want ActiveRecord...

9. mongo-ruby-driver
mongomapper
mongoid

10. 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)

11. Associations in Mongoid
class Post
include Mongoid::Document
field :title, :type => String
field :body, :type => String
has_many :comments
end
class Comment
include Mongoid::Document
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)

12. Keys, Validations, Timestamps & Hooks
class Post
include Mongoid::Document
include Mongoid::Timestamps
field :title, :type => String
field :body, :type => String
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

13. Versioning a Mongo Document
class Post
include Mongoid::Document
include Mongoid::Timestamps
include Mongoid::Versioning
field :title, :type => String
field :body, :type => String
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

14. Access related items
class Post
include Mongoid::Document
include Mongoid::Timestamps
include Mongoid::Versioning
field :title, :type => String
field :body, :type => String
field :slug, :type => String
has_many :comments
belongs_to_related :account
has_many_related :sources
.....
end
database.yml meet database.mongo.yml

15. 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

16. 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

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

18. “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) }

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

20. additional mongoid features
Composite Keys
Indexing
Inheritance
native MongoDB expressions