title: mongodb empty is the wildcard but only on top level?
body: <p>sorry to those who do not like Python my samples use pymongo.</p>
  
  <p>In mongodb empty is used as "wildcard" like the here (using the "wildcard" I get same or more results):</p>
  
  <pre><code>&gt;&gt;&gt; projects.find_one({'name': 'boodo3', '_id': ObjectId('4efa14c6b0ab584326000000')})
  {u'_id': ObjectId('4efa14c6b0ab584326000000'), u'name': u'boodo3', u'updated_at': u'2011-12-28 13:47:09'}
  &gt;&gt;&gt; projects.find_one({'name': 'boodo3'})
  {u'_id': ObjectId('4efa14c6b0ab584326000000'), u'name': u'boodo3', u'updated_at': u'2011-12-28 13:47:09'}
  </code></pre>
  
  <p>but if I am querying "inside" of the document the wildcards do not work any more like in the following sample:</p>
  
  <pre><code>&gt;&gt;&gt; testruns.find_one({'_parent': {'_coll': u'projects', '_id': '4efa14c6b0ab584326000000'}})
  {u'_parent': {u'_coll': u'projects', u'_id': u'4efa14c6b0ab584326000000'}, u'_id': ObjectId('4efa167eb0ab584351000002'), u'name': u'11121617', u'updated_at': u'2011-12-27 19:03:26'}
  &gt;&gt;&gt; testruns.find_one({'_parent': {'_coll': u'projects'}})
  &gt;&gt;&gt; &lt;no results here&gt;
  </code></pre>
  
  <p>I tried variations using '$in' and '$nin' but so far without luck. I hope there is some structured way of querying documents (I mean something besides regex). I would restructure my collections if necessary but I believe that flat documents are not the solution here. </p>
  
  <p>Does that mean I have to translate all the queries into dot-notation?
  Or are regex the way to query documents in mongodb?</p>
  
  <p>disclaimer: I do not intent to criticize mongodb or anything. This is my first app which uses mongodb and I want to learn how to query documents in mongodb.</p>