WARNING!!!
When I get excited, I talk fast.
Feel free to remind me to slow down.

FEEDBACK
@jnunemaker and @mongodb

WHY?
WHAT?
HOW?

WHY?

• Scaling, schmaling
• Hammer/Nail
• Example (Harmony http://harmonyapp.com)

WHAT?

INTRO
• Built For Speed
• Document/Collection Oriented
• Dynamic Queries and Indexes
• Replication and Failover

GREAT FOR
• Websites
• Caching
• High volume, low value
• High scalability
• Storage of program objects and json

NOT AS GREAT FOR
• Highly transactional
• Ad-hoc business intelligence
• Problems requiring SQL

INSTALLATION
• mkdir -p /data/db
• download, unzip, mongod run
• http://video.railstips.org/mongomapper-demo/

DATABASE
• same concept as mysql
• made up of collections

COLLECTION
• Think table, but with no schema
• For grouping documents into smaller query sets (speed)
• Eachtop level entity in your app would have its own collection
(users, articles, etc.)
• Indexable by one or more key

DOCUMENT
• Stored in a collection, think record or row
• Can have _id key that works like primary keys in MySQL
• Three options for relationships: embedded document, foreign
keys, or db reference

QUERYING
• db.collection.find({‘first_name’: ‘John’}) # finds all Johns
• db.collection.find({‘first_name’: /^J/}) # regex
• db.collection.find_first({‘_id’:1}) # finds first with _id of 1
• db.collection.find({‘age’: {‘$gt’: 21}}) # finds possible drinkers
• db.collection.find({‘author.first_name’:‘John’}) # subdocument
• db.collection.find({$where:‘this.age >= 6 && this.age <= 18’})

MORE QUERYING
• $in, $nin, $all, $ne, $gt, $gte, $lt, $lte, $size, $where
• :fields (like :select in active record)
• :limit, :offset for pagination
• :sort ascending or descending [[‘foo’, 1], [‘bar’, -1]]
• count and group (uses map/reduce)

HOW?

HOW DO YOU
USE IT WITH RUBY
• mongo-ruby-driver http://github.com/mongodb/mongo-ruby-
driver
• activerecord adapter http://github.com/mongodb/
activerecord-mongo-adapter
• mongorecord http://github.com/mongodb/mongo-
activerecord-ruby

NUNEMAPPER
(MONGOMAPPER)
• Mongo is not MySQL
• DSL for modeling domain should also teach you Mongo
• It sounded fun
• Major appreciation for ORM’s

FEATURES
• Typecasting • Create and Update with
single or multiple
• Callbacks(ActiveSupport
Callbacks) • Delete and Destroy and _all
counterparts
• Validations (using my fork of
validatable) • Find: id, ids, :all, :first, :last
• Connection and database • Associations
can differ per document

EXAMPLE
class User
include MongoMapper::Document
key :name, String, :required => true, :length => 5..100
key :email, String, :required => true, :index => true
key :age, Integer, :numeric => true
key :active, Boolean, :default => true
key :address, Address
many :articles
end
class Address
include MongoMapper::EmbeddedDocument
key :street, String
key :city, String
key :state, String, :length => 2
key :zip, Integer, :numeric => true, :length => 5
end

RANDOM AWESOMENESS
• Capped collections (think memcache, actually used for
replication)
• Upserts db.collection.update({‘_id’:1}, {‘$inc’:{‘views’:1}})
• Multikeys (think tagging and full text search)
• GridFS and auto-sharding

LINKS
• http://railstips.org/2009/6/3/what-if-a-key-value-store-mated-with-a-relational-database-system
• http://railstips.org/2009/6/27/mongomapper-the-rad-mongo-wrapper
• http://railstips.org/2009/7/23/getting-started-with-mongomapper-and-rails
• http://locomotivation.squeejee.com/post/117119353/mongodb-ruby-friendly-document-storage-
that-doesnt-rhyme
• http://mongodb.com/
• http://10gen.com

John Nunemaker
http://orderedlist.com
http://railstips.org