An Introduction To NoSQL & MongoDB

An Introduction ToNoSQL & MongoDB
Lee Theobald
Twitter: @Leesy
Email: Lee@LTheobald.co.uk

NoSQL
A form of database management system that is non-relational.
Systems are often schema less, avoid joins & are easy to scale.
The term NoSQL was coined in 1998 by Carlo Strozzi and then again in early 2009 with the no:sql(east) conference
A better term would have been “NoREL” but NoSQL caught on. Think of it more as meaning “Not Only SQL”

But Why Choose NoSQL?
Amount of data stored is on the up & up.
Facebook is rumoured to hold over 50TB of data in their NoSQL system for their inbox search
The data we store is more complex than 15 years ago.
Easy Distribution
With all this data is needs to be easy to be able to add/remove servers without any disruption of service.

Choose Your Flavour
Key-Value Store
Graph
BigTable
Document Store

Key-Value Store
Data is stored in (unsurpisingly) key/value pairs.
Designed to handle lots of data and heavy load
Based on a Amazon’s Dynamo Paper
Example: Voldermort (http://project-voldemort.com/) - Developed by the guys at LinkedIn

Graph
Focuses on modeling data & associated connections
Inspired by mathematical Graph Theory.
Example: FlockDB (http://github.com/twitter/flockdb) – developed by Twitter

BigTable / Column Families
Based on the BigTable paper from Google
Data is grouped by columns, not rows.
Example: Cassandra (http://cassandra.apache.org/) – Originally developed by Facebook, now and Apache project.

Document Store
Data stored as whole documents.
JSON & XML are popular formats
Maps well to an Object Orientated programming model
Example: CouchDB (http://couchdb.apache.org/) or …
{
“id”: “123”,
“name”: “Oliver Clothesoff”,
“dob”: {
“year”: 1985,
“month”: 5,
“day”: 12
}
}

MongoDB!
Short for humongous
Open source with development lead by 10Gen
Document Based
Schema-less
Highly Scalable
MapReduce
Easy Replication & Sharding

Familiar Structure
A MongoDB instance is made up of a number of databases.
These contain a number of collections & you can have collections nested under other collections.
Compare it to MySQL which has databases and tables.

Inserts – As Easy As Pie
use cookbook;
db.recipes.save({
“name”: “Cherry Pie”,
“ingredients”: [“cherries”, “pie”],
“cooking_time”: 30
});

Searching – A Piece Of Cake!
db.recipes.find({
“cooking_time”: { “$gte”: 10, “$lt”: 30 }
}
db.recipes.findOne()

Some More Advanced Syntax
Limiting Results
db.find().limit(10);
Skipping results
db.find().skip(5);
Sorting
db.find().sort({cooking_time: -1});
Cursors:
var cur = db.find().cursor();
cur.forEach( function(x) { print(tojson(x)); });

MapReduce
Great way of doing bulk manipulation or aggregation.
2 or 3 functions written in JavaScript that execute on the server.
An example use could be generating a list of top queries from some search logs.

Map Function
Takes some input of the form of key/value pairs, performs some calculations and returns 0 or more key/value pairs
map = function() {
if (!this.query) {
return;
}
emit (this.query, {count: 1});
}

Reduce Function
Takes the results from the map function, does something (normally combine the results) and produces output in key/value pairs
reduce = function(key, values) {
var count = 0;
values.forEach(function(v) {
count += v[‘count’];
}
return {count: count;}
}

Replica Sets
Master/Slave configuration
If your primary server goes down, one of the secondary ones takes overautomatically
Extremely easy to setup

Auto Sharding – Horizontal Scaling

Other Features
GridFS support – Distributed file storage
Geospatial indexing
It’s constantly in development so new features are being worked on all the time!

Why Not Try It Yourself
Download it at: http://www.mongodb.org
Online tutorial at:http://www.mongodb.org/display/DOCS/Tutorial
Some handy MongoDB sites:
MongoDB Cookbook: http://cookbook.mongodb.org/
Kyle Banker’s blog: http://kylebanker.com/blog/
There’salso a load of handyreferencecards, stickers and otherMongoDBfreebiesupfront!

Thanks For Listening
Any questions?

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http://paper.li	89
http://lanyrd.com	21
http://newsrivr.com	12
http://xianguo.com	12
http://feed.feedsky.com	9
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http://ayudamutuapadresenprocesodeduelo.blogspot.com	3
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An Introduction To NoSQL & MongoDB

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