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  • How to get to the key name of a referenced entity property from an entity instance without a datastore read in google app engine?

    - by Sumeet Pareek
    Consider I have the following models - class Team(db.Model): # say I have just 5 teams name = db.StringProperty() class Player(db.Model): # say I have thousands of players name = db.StringProperty() team = db.ReferenceProperty(Team, collection_name="player_set") Key name for each Team entity = 'team_' , and for each Player entity = 'player_' By some prior arrangement I have a Team entity's (key_name, name) mapping available to me. For example (team_01, United States Of America), (team_02, Russia) etc I have to show all the players and their teams on a page. One way of doing this would be - players = Player.all().fetch(1000) # This is 1 DB read for player in players: # This will iterate 1000 times self.response.out.write(player.name) # This is obviously not a DB read self.response.out.write(player.team.name) #This is a total of 1x1000 = 1000 DB reads That is a 1001 DB reads for a silly thing. The interesting part is that when I do a db.to_dict() on players, it shows that for every player in that list there is 'name' of the player and there is the 'key_name' of the team available too. So how can I do the below ?? players = Player.all().fetch(1000) # This is 1 DB read for player in players: # This will iterate 1000 times self.response.out.write(player.name) # This is obviously not a DB read self.response.out.write(team_list[player.<SOME WAY OF GETTING TEAM KEY NAME>]) # Here 'team_list' already has (key_name, name) for all 5 teams I have been struggling with this for a long time. Have read every available documentation. I could just hug the person that can help me here :-) Disclaimer: The above problem description is not a real scenario. It is a simplified arrangement that represents my problem exactly. I have run into it in a rater complex and big GAE appication.

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  • Google App Engine - Is os.environ reset between requests?

    - by Ian Charnas
    Hello I can't think of a way to test this and was hoping someone here knew the answer... I'm storing some request-specific data in os.environ, and was wondering if that data was going to leak to other requests. Does anyone know? Yes I realize that it's normal to use request.environ for this, and usually I do, but I want to store the currently authorized user ID (I'm using custom auth, not GAE auth) inside os.environ so that the models know the currently logged in user (remember, they don't have access to request.environ) without me having to pass the request object to just about every single model method. any help would be greatly appreciated Ian

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  • database modeling for google app engine for multiple revison of entity.

    - by iamgopal
    hi, in my application ( kind of wiki clone ) - an article is frequently changing. and i need to track all changes that are done on that article. { text only. } one crude way i have done it, is to add a datetime property and create a new entity everytime something change. which is too much database wasting. { and also un-necessary index waste too. } and also need to re-create parent-child and entity relationships. i also have log which can show changes -- but i want some thing easier , so that jumping from one version to another version could be easier. ideas ? thanks.

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  • [app-engine-java-groovy] One-to-Many relationship. Select objects from datastore.

    - by Olexandr
    Hi. I've omitted some code(package declarations, imports, other fields) for shortness. I have here simple One-to-Many relation. It worked fine till this moment. @PersistenceCapable(identityType = IdentityType.APPLICATION, detachable="true") class Restaurant implements Serializable { @PrimaryKey @Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY) Key id @Persistent(mappedBy = "restaurant") List<RestaurantAddress> addresses = new ArrayList<RestaurantAddress>() } //-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= @PersistenceCapable(identityType = IdentityType.APPLICATION, detachable="true") class RestaurantAddress implements Serializable { @PrimaryKey @Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY) Key id @Persistent Restaurant restaurant } Now i need to get(select) all the Restaurants from DB: def getRestaurantsToExport(final String dst, final int count) { String field = restaurantExportFields[dst] return transactionExecute() { PersistenceManager pm -> Query q = pm.newQuery(Restaurant.class) q.filter = "$field == null" q.setRange(0, count) return q.execute() } } But there are on problem - query gives me 12 restaurants(as in DB) but every Restaurant has 0 Address but in Datastore every Restaurant has minimum 2 addresses. Have anyone the same problem or knows the solution ?

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  • Using low level api for datastore in google app engine ? is it bad ?

    - by Chez
    There is little documentation on how to use the low level api for datastore and quite a lot on JPA and JDO and how it translates to it. My question is: is there any advantage in coding against the JPA or JDO specs instead of accessing directly the low level api for datastore ? From an initial look, it seems simple and straight forward but I am not sure if there are good reasons why not to do it. Thanks Cx

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  • App Engine List<String> DB adds chars before string?

    - by Donalds
    Hi, I have a field in my db which is a List. I add strings to that list and it works fine on the development server. This is the result: [mat12, bg10] When I do the same on the deploy server, this is the result: [u'mat12', u'bg10'] I don't understand why it adds "u' '" to the string. I would really appreciate your help. Thanks

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  • Google App Engine/GWT/Eclipse Plugin Newbie Question- how to autobuild client side resources?

    - by Dieter Hanover
    Hi there, I'm tinkering with the default GWT application generated by the Google Eclipse plugin when I click the Google "New Web Application Project" button in Eclipse 3.5. This will no doubt be familiar to many of you.. basically there is an h1 title stating "Web Application Starter Project," a text field, and a Send button. What I've found is that whenever I make changes to the client side resources, e.g. change the text on the Send button to "Submit" in the .java file, Eclipse does not appear to autobuild these resources. In fact I have to rebuild the entire project in order for these changes to be reflected in my browser. I do have "build automatically" selected in eclipse. I should state that this is my second GWT project, the first was almost entirely server side (restlet on GAE) and everything built automatically nicely. When I first tried this new project with updated client resources, on refreshing my browser, the browser stated "you may need to (re)compile your project." I'm not sure if this is relevant but I thought I'd mention it all the same. So what's going on? How do I get Eclipse/GWT to autobuild these client side resources? Cheers for any help you can offer! :-)

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