Thanks Nick. Always appreciate the help!
Regarding the prefix you put in the key_name, on hunch it looks to
have other benefits. I suspect memcache. Do you have any other
pearls you can toss out about it, and ways that known key_name
prefixes can be leveraged?
--Daniel Rhoden
On Aug 17, 2009, at 5:21 AM, Nick Johnson (Google) wrote:
> Hi Daniel,
>
> The best way to ensure uniqueness is to use key names. In this case,
> the natural key name is the User's ID. For example:
>
> user_account = Account(key_name = 'user:%d' %
> (current_user.user_id(),), ...)
>
> This also allows you to look up user accounts without a query:
>
> user_account = Account.get_by_key_name('user:%d' %
> (current_user.user_id(),))
>
> -Nick Johnson
>
> On Mon, Aug 17, 2009 at 2:45 AM, Daniel Rhoden <[email protected]>
> wrote:
> I discovered that my 'Account' model happily created multiple
> instances of user '[email protected]' without complaint during
> testing. (I know, fix my code).
>
> Short question: What's the lightest way of ensuring value uniqueness
> between entity values?
>
> I've read up on the Property class constructor argument "validator"
> and got to wondering if there is a RoR-like library of prefab
> validators. It would be great if I could do something like this:
>
> from google.appengine.ext import validation
>
> class Account(db.Model):
> user = db.UserProperty(required=True,
> validator=validation.unique(db.UserProperty) )
> ...
>
> related resources:
> http://code.google.com/appengine/docs/python/datastore/propertyclass.html
> http://googleappengine.blogspot.com/2009/07/writing-custom-property-classes.html
>
> --Daniel Rhoden
>
>
>
>
>
>
>
>
> --
> Nick Johnson, Developer Programs Engineer, App Engine
>
> >
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