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A brief overview of currently popular & available key/value, column oriented & document oriented databases, along with implementation suggestions for the CakePHP web application framework.
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NON-RELATIONAL DATABASES
Saturday, October 31, 2009
@JPERRAS - JOEL PERRASCanadian Geek
Blog: http://nerderati.com
GitHub: http://github.com/jperras
CakePHP Core since Early 2009, PHP dev. since 2001
McGill University, Montréal, Canada - Physics, Mathematics & Computer Science
Employer: Plank Design (http://plankdesign.com) (Twitter: @plankdesign)
Saturday, October 31, 2009
RELATIONAL DATABASES
Many different vendors: MySQL, PostgreSQL, SQLite, Oracle, ...
Same basic implementation:
B(+)-Trees for pages
B(+)-Trees or hash tables for secondary indexes
Possibly R-Trees for spatial indexes
Saturday, October 31, 2009
WHAT THEY’RE GOOD AT
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Schemas (relational models)
Familiar BCNF structure
Strong consistency
Transactions
Very “mature” & well tested (mostly)
Easy adoption/integration
Saturday, October 31, 2009
FriendFeed
Wikipedia
Google AdWords
RDBMS’ES ARE NOT GOING ANYWHERE
Saturday, October 31, 2009
Most small to medium size applications willnever need to go beyond a single database server.
Saturday, October 31, 2009
Always try and follow the Golden Web ApplicationDevelopment Rule:
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DON’T TRY TO SOLVE A PROBLEM YOU DON’T
HAVE
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The web has created new problem domains in data storage and querying.
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Often use variable schemas
Optional fields: contact lists, addresses, favourite movies/books, etc.
NULL-itis: null values should not be permitted in BCNF, but are everywhere in web applications.
MODERN WEB APPS
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‘Social’ apps => high write/read ratios
Complex Many-to-Many relationships
Joins become a problem in federated architectures
Eventual consistency is usually acceptable
Downtime unacceptable
MODERN WEB APPS
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OTHER CONCERNS
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RULES OF APP AGINGhttp://push.cx/2009/rules-of-database-app-aging
1. All fields become optional2. All relationships become many-to-many3. Chatter (comments explaining hacks) grows with time.
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SOME GOOD PROBLEMS TO HAVE
Even if they are “Hard” ones to solve.
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Load Balancing(you can only live with one machine for so long)
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High Availability(because disks fail, and replication fails)
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What’s a web application developer to do?
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Alternative Data Storage Solutions
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Not a silver bullet.
These can solve some problems, but cause others and have their own limitations.
It’s up to you to weigh the cost/benefit of your chosen solution.
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THE LANDSCAPE
Key/Value Stores/Distributed Hash Tables (DHT)
Document-oriented databases
Column-oriented databases
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KEY/VALUE STORES
Voldemort
Scalaris
Tokyo Cabinet
Redis
MemcacheDB
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DOCUMENT ORIENTED DATA STORES
CouchDB <- (my favourite!)
MongoDB
SimpleDB (Amazon)
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COLUMN-ORIENTED STORES
BigTable (Google)
HBase (Hadoop Database)
Hypertable (BigTable Open Source clone)
Cassandra (Facebook)
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How do we use these technologiesalongside CakePHP ?
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This year’s magical word:
DataSources
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CASE STUDY - COUCHDB
http://github.com/jperras/divan(I will make zip/tar available when more stable - stay tuned)
Saturday, October 31, 2009
CASE STUDY - TOKYO CABINET/TYRANT
http://github.com/jperras/tyrannical(I will make zip/tar available when more stable - stay tuned)
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Non-relational stores are not relational.
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So don’t try to force the interface tobe relational.
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DESIGNING A NON-RELATIONAL DATASOURCE
Favour simplicity over transparency
Don’t try to implement everything that the MySQL driver implements
Use the strengths of the alternative store
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Example Use Cases
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KEY/VALUE STORES
Most have atomic increment/decrement operations
Great for API rate limiters (e.g. 300 API reqs/hour/account)
Counts & sums of normalized data
Most popular items, votes, ratings, some statistics
And more.
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DOCUMENT STORES
Filesystem objects (pdfs, images, excel sheets etc.) - stored as document attachments (size limited).
Allows you to reduce reliance on shared filesystems (NFS)
Address book
Volatile schema situations
CouchDB has a very interesting feature set
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There are many, many use cases.
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Thanks to the DataSource adapter implementation in CakePHP, creating a model-based interface is simple.
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Thank you!
@jperrashttp://nerderati.com
http://github.com/jperrasSaturday, October 31, 2009
CODE
Divan - CouchDB datasource
Yantra - State Machine component for application control flow
CakPHP TextMate Bundle
CakeMate - TextMate/Vim Plugin
Tyrannical - Tokyo Tyrant datasource
Originally by Martin Samson ([email protected])
Working to improve code - commits coming soon.
Currently working on a framework-agnostic, distributed, plugin/library server.
Saturday, October 31, 2009
