open-source, high-performance,
schema-free, document-oriented
database

RDBMS
• Great for many applications
• Shortcomings
• Scalability
• Flexibility

CAP Theorem
• Consistency
• Availability
• Tolerance to network Partitions
• Pick two
http://www.cs.berkeley.edu/~brewer/cs262b-2004/PODC-keynote.pdf

ACID vs BASE
• Atomicity
• Basically Available
• Consistency
• Soft state
• Isolation
• Eventually consistent
• Durability

Schema-free
• Loosening constraints - added flexibility
• Dynamically typed languages
• Migrations

BigTable
• Single master node
• Row / Column hybrid
• Versioned

BigTable
• Open-source clones:
• HBase
• Hypertable

Dynamo
• Simple Key/Value store
• No master node
• Write to any (many) nodes
• Read from one or more nodes (balance
speed vs. consistency)
• Read repair

Dynamo
• Open-source clones
• Project Voldemort
• Cassandra - data model more like
BigTable
• Dynomite

memcached
• Used as a caching layer
• Essentially a key/value store
• RAM only - fast
• Does away with ACID

Redis
• Like memcached
• Different
• Values can be strings, lists, sets
• Non-volatile

Tokyo Cabinet + Tyrant
• Key/value store with focus on speed
• Some more advanced queries
• Sorting, range or prefix matching
• Multiple storage engines
• Hash, B-Tree, Fixed length and Table

• A lot in common with MongoDB:
• Document-oriented
• Schema-free
• JSON-style documents

• Differences
• MVCC based
• Replication as path to scalability
• Query through predefined views
• ACID
• REST

• Focus on performance
• Rich dynamic queries
• Secondary indexes
• Replication / failover
• Auto-sharding
• Many platforms / languages supported

Good at
• The web
• Caching
• High volume / low value
• Scalability

Less good at
• Highly transactional
• Ad-hoc business intelligence
• Problems that require SQL

Ruby support
• mongo-ruby-driver
• Pure Ruby, with optional C extension
• MongoRecord
• ORM like functionality
• Other mappers

Basics
• Connect:
• db = Mongo.new.db(‘my-database’)
• coll = db.collection(‘players’)
• Insert:
• coll.insert (“name” => “mike”, “age” => ...
• Query:
• coll.find (“age” => 35)

Advanced queries
• Sorting
• Limit
• $gt, $lt, $gte, $lte, $ne, $all, $in, $nin
• where()
• count()
• group()

GridFS
• File storage in MongoDB
• IO-like API for Ruby

Other cool stuff
• Capped collections
• Upserts
• Multikeys

Demo

• Download MongoDB
http://www.mongodb.org
• Install the Ruby driver
• Try it out!

• http://www.mongodb.org
• irc.freenode.net#mongodb
• mongodb-user on google groups
• @mongodb
• mike@10gen.com