title: Why is PyMongo count_documents is slower than count?
body: <p>In <code>db['TF']</code> I have about 60 million records.</p>
  
  <p>I need to get the quantity of the records.</p>
  
  <p>If I run <code>db['TF'].count()</code>, it returns at once.</p>
  
  <p>If I run <code>db['TF'].count_documents({})</code>, that is a such long time before I get the result.</p>
  
  <p>However, the <code>count</code> method will be deprecated.</p>
  
  <p>So, how can I get the quantity quickly when using <code>count_documents</code>? Is there some arguments I missed?</p>
  
  <p>I have read the doc and code, but nothing found.</p>
  
  <p>Thanks a lot!</p>