Appengine Django/GQL – Ensuring Uniqueness of Model Type on Edit – Not Equals Filters

Edit 2009-02-02 - Added note about inequality query complexity. Spoiler – inequalities are 2 queries under the hood. In my further adventures in Google AppEngine land, I wanted to ensure uniqueness of an email field while still allowing the user to change their email address. Since, Google App Engine’s BigTable doesn’t allow you to custom define unique indexes, this poses a...