title: How to transfer multiple entities for NDB Model in Google App Engine for python?
body: <p>I have an NDB model. Once the data in the model becomes stale, I want to remove stale data items from searches and updates. I could have deleted them, which is explained in <a href="https://stackoverflow.com/questions/18945109/how-to-delete-all-entities-for-ndb-model-in-google-app-engine-for-python">this SO post</a>, if not for the need to analyze old data later. 
  I see two choices</p>
  
  <ol>
  <li>adding a boolean status field, and simply mark entities deleted</li>
  <li>move entities to a different model</li>
  </ol>
  
  <p>My understanding of the trade off between these two options</p>
  
  <ol>
  <li>mark-deleted is faster</li>
  <li>mark-deleted is more error prone: having extra column would require modifying all the queries to exclude entities that are marked deleted. That will increase complexity and probability of bugs.</li>
  </ol>
  
  <p>Question: 
  Can move-entities option be made fast enough to be comparable to mark-deleted?
  Any sample code as to how to move entities between models efficiently?</p>
  
  <p>Update: 2014-05-14, I decided for the time being to use mark-deleted. I figure there is an additional benefit of fewer RPCs.</p>
  
  <p>Related:</p>
  
  <ol>
  <li><a href="https://stackoverflow.com/questions/18945109/how-to-delete-all-entities-for-ndb-model-in-google-app-engine-for-python">How to delete all entities for NDB Model in Google App Engine for python?</a></li>
  </ol>