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Editorial Team
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Asked: 2026-05-27T00:35:50+00:00

I have a message model and I want it to have several receivers, possibly

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I have a message model and I want it to have several receivers, possibly a lot of them.
I would also like to be able to tell for each receiver if the message was viewed or not (read/unread). Also I would like a receiver to be able to delete the message.

The two possible solutions are the following, for each I have a Message model an User model.

  • For the first (using the ideas presented here http://www.google.com/events/io/2009/sessions/BuildingScalableComplexApps.html)

    I have a MessageReceivers class which has a ListProperty containing the users that will receive the message and set the parent to the message. I query of this with messages = db.GqlQuery('SELECT __key__ FROM MessageReceivers WHERE receivers = :1', user) and the do a db.get([ key.parent() for key in messages ]).

    The problem I have which this is that I’m not sure how to store the state of the message: whether it is read or not and a subsequent issue whether the user has new messages. An additional issue would be the overhead of deleting a message (would have to remove user from receivers list property)

  • For the second: I have a MessageReceiver for each receiver it has links to message and to user and also stores the state (read/unread).

Which of this two approached do you consider that it has a better performance? And in the case of the first do you have any suggestion on handling the status of the message.

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  1. Editorial Team

    I’ve implement first option in production. Drawback is that ListProperty is limited to 2500 entries if you use custom index. Shameless plug: See my blog bost http://bravenewmethod.wordpress.com/2011/03/23/developing-on-google-app-engine-for-production/

    Read state storing. I did this by implementing an entity that stored unread messages up to few months back and then just assumed older ones read. Even simpler is to query the messages in date order, and store the last known message timestamp in entity and assume all older as read. I don’t recommended keeping long history in entity with huge list property, because reading and storing such entities can get really slow.

    Message deletion is expensive, no way around that.

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