title: Column <x> has dtype object, cannot use method 'nsmallest' with this dtype
body: <p>Any query I try on my table complains that</p>
  
  <pre><code>Column 'time' has dtype object, cannot use method 'nsmallest' with this dtype
  </code></pre>
  
  <p>However, when I look at the table source that I queried, the schema reports types of long. In this case, I am querying Treasure Data.</p>
  
  <p>How then do I sort my dataframe by a column value and the the one with the least?</p>