title: What is the query that is used in when I use square brackets with an sqlalchemy query?
body: <p>When use the following query:</p>
  <pre><code>Foo.query.filter_by(bar=&quot;bar&quot;)[:20]
  </code></pre>
  <p>Do all the objects that matches the filter get loaded and I only choose the first 20 or are the first 20 objects only get loaded. And if the second, is there a way to load only a specific number of objects ?</p>
  <p>Thanks in advance guys.</p>