OCRuby Feb 26, 2000 meeting minutes

Thought I'd post this here since the OCRuby group submission is moderated.

This is mainly interesting for the Mongo DB presentation by Tommy Chheng.

Attendees:

Dash

Tina

Michael Hartl

Tommy Chheng

Scott Smith

Michael has published 7 chapters of his electronic book at railstutorial.org

Tommy: Whither Mongo DB for Natural Development

Used by:

• github
• EA
• The New York Times
• sourceforge
• The Business Insider

The above are "big" sites.

Why?

• NoSQL trend?
• Scalability?
• Natural Development!

Compare

SQL fixed schema

• Data model Rows/Tables
• Data Types Primitives

MongoDB Dynamic

• BSON Documents/Collections
• Primitives+Arrays/Hashes

Records vs Documents

SQL

3 tables

• Documents
• Revisions
• Tags

MongoDB

• document = {title:...} (reads as Javascript code)
• BSON data structure naturally maps to most programming languages hash object.
• ORM can just be a thin layer.
• Can debug Mongo a lot easier.

Mongo Install

• http://www.mongodb.org/display/DOCS/Quickstart
• Chef recipe available
• http://github.com/schisamo/
• chef_cookbooks/
• Start server: ./mongod
• Run console: mongo
• Works with javascript as the query language

How to use in Ruby?

Easy to use in Rails or Sinatra

2 gems

• mongo+mongo_ext gem
• mongo_mapper gem

http://groups.google.com/group/mongodb-user

MongoMapper Models

• No Migrations!
• AR Validations
• AR Callbacks
• Testing using Facory Girl
• Rails 3?
• fork which uses ActiveModel, see mailinglist
• is complete but not merged in yet.

MongoMapper Model

(sample code)

CouchDB or MongoDB?

CouchDB

• One big database
• HTTP REST
• Find by id ma/reduce JS functions
• MVCC

MongoDB

• Many collections
• sockets
• Find by id - dynamic JS queries
• Update in place

MVCC - updates by making new version copy; good for data safety.

Update in place is a lot faster

MongoDB by default writes to disk in batches

Limitations

Memory Mapped file:

• 32-bit 4GB limit, use 64-bit

Atomic updates only at document level

• Solve by nesting related data in document

MongoDB lacks:

• transactions
• CouchDB-style MVCC revisioning

http://www.mongodb.org/display/DOCS/Atomic

Author

Blog http://tommy.chheng.com

Twitter @tommychheng

Side project: http://nextsprocket.com/

• using mongoDB + mongo_mapper!