title: SQLAlchemy doesn't recognize new entries in query
body: <p>I'm querying the latest entry from a table like this:</p>
  <pre class="lang-py prettyprint-override"><code>data = dbsession.query(db.mytable).order_by(db.mytable.timestamp.desc()).with_entities(db.mytable.timestamp).first()
  </code></pre>
  <p>On startup this is fine, but if new etries are added by the same dbsession during runtime, the query above doesn't recognize them.
  But the following code without SQLAlchemy works as expected:</p>
  <pre class="lang-py prettyprint-override"><code>sql_query=&quot;SELECT timestamp FROM mytable ORDER BY timestamp DESC LIMIT 1&quot;
  data = cursor.execute(sql_query)
  </code></pre>
  <p>How do I get SQLAlchemy to work in this case?</p>