title: Mass updates in Google App Engine Datastore
body: <p>What is the proper way to perform mass updates on entities in a Google App Engine Datastore? Can it be done without having to retrieve the entities?</p>
  
  <p>For example, what would be the GAE equivilant to something like this in SQL:</p>
  
  <pre><code>UPDATE dbo.authors
  SET    city = replace(city, 'Salt', 'Olympic')
  WHERE  city LIKE 'Salt%';
  </code></pre>