title: Pymongo query on a cursor
body: <p>I have a large collection (73 million entries) that I want to do operations on. First I want to query away ~98% of the data, and then do larger operations on the last 2%. First I do</p>
  <pre><code>query_cursor = collection.find({'score': {'$gt': threshold}}) 
  </code></pre>
  <p>which returns a cursor of the query. Writing this to a list and doing the operations on the list is much slower than if I had the option to re-query this cursor with fx</p>
  <pre><code>query_cursor.find({'filename': 'abc'})
  </code></pre>
  <p>However, because I need to do multiple operations on it, it's not feasible to constantly do</p>
  <pre><code>query_cursor = collection.find({'score': {'$gt': threshold}, 'filename': 'abc'}) 
  </code></pre>
  <p>So is there a way to query onto the cursor?</p>