To Redis or Not To Redis? (Key-Value Stores Part 4) | Engine Yard Blog

To Redis or Not To Redis? (Key-Value Stores Part 4) | Engine Yard Ruby on Rails Blog:

Second, notice that you don’t need to initialize a counter before using it. If you reference a key in an increment or decrement operation that doesn’t exist, it will be automatically vivified for you. Finally, as mentioned just a moment ago, numbers don’t appear anywhere in the list of Redis data types, so the increment/decrement operations work on a simple principle—try to interpret the value as a long, and then work with whatever you get. So, be careful not to increment or decrement a key that has non-numeric data in it. Rather than throwing some sort of exception, Redis will happily attempt to do what you are asking, and clobber your data along the way.

Full article: http://www.engineyard.com/blog/2009/key-value-stores-for-...