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POApp Engine Messaging System with Message Status - Design Pattern
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  1. POApp Engine Messaging System with Message Status - Design Pattern
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    copied!<p>I'm building a Threaded Messaging System that will be hosted on Google AppEngine</p> <p>I've modeled it after the technique described by Brett Slatkin in <a href="http://www.google.com/events/io/2009/sessions/BuildingScalableComplexApps.html" rel="nofollow">Building Scalable, Complex Apps on App Engine</a></p> <pre><code>class Message(db.Model): sender = db.StringProperty() body = db.TextProperty() class MessageIndex(db.Model): receivers = db.StringListProperty() </code></pre> <p>The issue I'm having to determining the most efficient way to track the message state for a User. For example is a message <code>read</code>, <code>archived</code>, <code>deleted</code> for a particular user.</p> <p>Here are the solution I have come up with so far.</p> <p>I'm using <a href="http://code.google.com/p/appengine-ndb-experiment/" rel="nofollow">Datastore+</a>'s StructuredProperty to add a state to the message <code>MessageIndex</code></p> <pre><code>class Message(model.Model): sender = model.StringProperty() body = model.TextProperty() class _DisplayState(model.Model): user_key = model.KeyProperty() state = model.IntegerProperty(default=0) # 0-unread, 1-read, 2-archived class MessageIndex(model.Model): receivers = model.StructuredProperty(_DisplayState, repeated=True) </code></pre> <p>This solution, while simple, negates the benefit of the MessageIndex. Additionally since the the MessageIndex is in the same entity group as the message datastore writes will be limited.</p> <p><a href="https://gist.github.com/1025736" rel="nofollow">Full Source Code</a></p> <p>What would be the most efficient way to accomplish this? Would adding an additional entity group be a better solution?</p> <pre><code>class MessageState(model.Model): user_key = model.KeyProperty() message_key = model.KeyPropery() message_state = model.IntegerProperty(default=0) # 0-unread, 1-read, 2-archived </code></pre>
 

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