MongoDB & Mongoid with Rails

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Brown bag presentation on using MongoDB and Mongoid with Rails.

Published in: Technology

MongoDB & Mongoid with Rails

  1. 1. MongoDB { name: “mongo”, type: “db” }
  2. 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. 3. built for speed document/collection oriented dynamic queries and indexes replication and failover
  4. 4. websites from yesterday and today high volume traffic high scalability storage of objects and JSON
  5. 5. caveats
  6. 6. no transactions
  7. 7. relationships
  8. 8. MongoDB with Ruby because we all want ActiveRecord...
  9. 9. mongo-ruby-driver mongomapper mongoid
  10. 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. 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. 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. 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. 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. 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. 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. 17. arithmetic, grouping & aggregation #max, #min, #sum, #aggregate, #group
  18. 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. 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. 20. additional mongoid features Composite Keys Indexing Inheritance native MongoDB expressions
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