title: How to assign default value to all NDB datastore entries?
body: <p>I have to add one new property to my existing NDB class:</p>
  
  <pre><code>class AppList(ndb.Model):
      ...
      ignore = ndb.BooleanProperty(default=False) # new property
  </code></pre>
  
  <p>Then I will use it like below:</p>
  
  <pre><code>entries = AppList.query()
  entries = entries.filter(AppList.counter &gt; 5)
  entries = entries.filter(AppList.ignore == False)
  entries = entries.fetch()
  </code></pre>
  
  <p>I can not use <code>AppList.ignore != True</code> to catch early added records (which don't have <code>ignore</code> property), so I have to assign <code>False</code> for all records in my <code>AppList</code> entity. What is the most effective way to do it? Currently this entity contains about 4'000 entries. </p>
  
  <p><strong>Upd</strong>. I've decided to use the following ugly code (didn't manage to apply <code>cursors</code>), it runs as a cron job. But don't I update the same 100 records each time?</p>
  
  <pre><code>entities = AppList.query()
  # entities = entities.filter(AppList.ignore != False)
  entities = entities.fetch(100)
  while entities:
      for entity in entities:
          entity.ignore = False
          entity.put()
      entities = AppList.query()
      # entities = entities.filter(AppList.ignore != False)
      entities = entities.fetch(100)
  </code></pre>