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4706003
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2011-01-16T14:53:03.543
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2015-11-28T14:44:36.290
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2015-11-28T14:44:36.290
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1843331
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2906746
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2
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Instead of what <a href="http://code.google.com/appengine/articles/update_schema.html" rel="nofollow">the docs</a> suggest, I would suggest to use low level GAE API to migrate. The following code will migrate all the items of type <code>DbMyModel</code>: <ul> <li><code>new_attribute</code> will be added if does not exits. </li> <li><code>old_attribute</code> will be deleted if exists. </li> <li><code>changed_attribute</code> will be converted from boolean to string (<code>True</code> to Priority 1, <code>False</code> to Priority 3)</li> </ul> Please note that <code>query.Run</code> returns iterator returning <code>Entity</code> objects. <code>Entity</code> objects behave simply like <code>dict</code>s: <pre><code>from google.appengine.api.datastore import Query, Put query = Query("DbMyModel") for item in query.Run(): if not 'new_attribute' in item: item['attribute'] = some_value if 'old_attribute' in item: del item['old_attribute'] if ['changed_attribute'] is True: item['changed_attribute'] = 'Priority 1' elif ['changed_attribute'] is False: item['changed_attribute'] = 'Priority 3' #and so on... #Put the item to the db: Put(item) </code></pre> In case you need to select only some records, see the <code>google.appengine.api.datastore</code> module's source code for extensive documentation and examples how to create filtered query. Using this approach it is simpler to remove/add properties and avoid issues when you have already updated your application model than in GAE's suggested approach. For example, now-required fields might not exist (yet) causing errors while migrating. And deleting fields does not work for static properties. 
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1. POUpdating Model Schema in Google App Engine?
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1. PTAnswer
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1. USTim Castelijns
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1. USAlek Kowalczyk
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