MongoDB SF Python

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

PyMongo • Python driver for MongoDB • Pure Python, with optional C extension • Installation • Use setuptools: easy_install pymongo

Basics • Connect: • Insert: • Query:

Document values • None • Special values: • bool • SON • int • Binary • ﬂoat • ObjectId • string / unicode • DBRef • dict • datetime.datetime • compiled re

• Schema-free: • Query with selectors:

Advanced queries • Sorting: • Limit: • Range:

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

GridFS • File storage in MongoDB • File-like API for Python • Initialize: • Write: • Read:

Other cool stuff • Capped collections • Upserts • Multikeys

Demo

• Download MongoDB http://www.mongodb.org • Install PyMongo • Try it out!

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

MongoDB SF Python

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