I building a user system and decided to use the Gravatar (I know, I know) system for user icons.
Since Im already accessing the database to grab user data, I was wondering if it made sense to store the users's gravatar URL in the database so I didn't have to take their email address and MD5 it every time it is used.
In PHP 5.2.X - And I assume that MD5 is pretty quick. But wouldn't it be quicker not to do it an just grab it from the DB?
Storing and retrieving the extra data in each database row would likely take more time than the md5 would. MD5 is a very fast operation, especially on input as small as an email address.
There's no way doing one MD5 is slowing you down. If you're really so worried about it, do it in Javascript on the client side, since you don't need the Gravatar - the users do.
This is provided that you expose the email addresses, of course.