This document provides an overview of non-relational databases and MongoDB. It discusses the advantages of non-SQL databases like scalability and flexibility compared to RDBMS. It also covers MongoDB features like document-oriented data structures, dynamic queries, indexing, replication and sharding. Examples of MongoDB operations like inserting, finding and querying documents are also shown.

1. nonSQL databases
alexey gaziev

2. RDBMS
• Great for many apps
• Shortcomings
• Scalability
• Flexibility

3. Other DBMS
• Flat file
• Hierarchical
• Network
• Document-oriented
• Object-oriented

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

5. ACID & BASE
• Atomicity • Basically Available
• Consistency • Soft state
• Isolation • Eventually consistent
• Durability

6. ACID vs. BASE
ACID BASE
• Strong consistency • Weak consistency
• Isolation • Availability first
• Focus on “commit” • Best effort
• Nested transactions • Approximate answers
• Availability? • Agressive (optimistic)
• Conservative • Simpler!
• Difficult evolution • Faster
(schema)
• Easier evolution

8. Scalability & Intro
Performance
memcached
Key/Values store
RDBMS
Depth of Functionality

9. Features
• Collection oriented storage: easy storage of object/
JSON -style data
• Dynamic queries
• Full index support, including on inner objects and
embedded arrays
• Query profiling
• Replication and fail-over support
• Efficient storage of binary data including large objects
(e.g. photos and videos)
• Auto-sharding for cloud-level scalability (currently in
alpha)
• Commercial support available

10. Great for
• Websites
• Caching
• High volume, low value
• High scalability
• Storage of program objects and json

11. Not as great for
• Highly transactional
• Ad-hoc business intelligence
• Problems requiring SQL

12. Installation

13. Collection
• Think table, but with no schema
• For grouping into smaller query sets (speed)
• Each top entity in your app would have its own
collection (users, articles, etc.)
• Full index support

14. Document
• Stored in collection, think record or row
• Can have _id key that works like primary key in
MySQL
• Two options for relationships: subdocument or
db reference

15. Storage (BSON)
{ author: 'joe',
created: Date('03-28-2009'),
title: 'Yet another blog post',
text: 'Here is the text...',
tags: [ 'example', 'joe' ],
comments: [ { author: 'jim', comment: 'I disagree' },
{ author: 'nancy', comment: 'Good post' }
]
}

16. Basics
$ bin/mongod &
$ bin/mongo
...
> use mydb
> j = { name: "mongo"};
{"name" : "mongo"}
> t = { x : 3 };
{ "x" : 3 }
> db.things.save(j);
> db.things.save(t);
> db.things.find();
in cursor for : DBQuery: example.things ->
{"name" : "mongo" , "_id" : "497cf60751712cf7758+dbb"}
{"x" : 3 , "_id" : "497cf61651712cf7758+dbc"}
>

17. 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’})

18. Querying 2
• $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)

19. Dynamic querying

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

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

22. Grid FS
• File storage in MongoDB
• IO-like API for Ruby

23. Other cool stuff
• Capped collections
• Upserts
• Multikeys

24. Resources
• http://spitfiresky.com/blog/recap-of-my-sdruby-
presentation-on-mongodb.html
• http://railstips.org/2009/6/3/what-if-a-key-
value-store-mated-with-a-relational-database-
system
• http://www.mongodb.org/display/DOCS/
Production+Deployments
• http://www.mongohq.com/home

25. Resources 2
• http://api.mongodb.org/ruby/0.15.1/index.html
• http://www.engineyard.com/blog/2009/
mongodb-a-light-in-the-darkness-key-value-
stores-part-5
• http://queue.acm.org/detail.cfm?id=1394128

26. thanks!