title: Unique Constraint At Data Level in GAE
body: <p>It seems that the <code>unique</code> constraint is not natively supported in GAE, although <a href="http://squeeville.com/2009/01/30/add-a-unique-constraint-to-google-app-engine/" rel="nofollow noreferrer">one can enforce <code>unique</code> check before <code>putting</code> an object to store</a>.  </p>
  
  <p>But that was in January 2009, what about now? Can I specify <code>unique</code> constraint on a column during schema creation? i.e.</p>
  
  <pre><code>class Account(db.Model):
    name = db.StringProperty()
    email = db.StringProperty() as unique # something like this
    @classmethod
    def create(cls, name, email):
      a = Account(name=name, email=email)
      a.put()
      return a
  </code></pre>