title: Why %time output is Wall time: 0 ns in Jupyter Notebook with IPython?
body: <p>I try to measure query speed in my jupyter notbook</p>
  
  <pre><code>%time
  a10= pd.read_sql('SELECT t.id, t.order_id FROM transactions.t', con=db_connection)
  </code></pre>
  
  <p>Whatever my query is the output always</p>
  
  <pre><code>Wall time: 0 ns
  </code></pre>
  
  <p>I assume  <code>%time</code> is not related with previous cell, this cell requires more than 10s to execute, why <code>Wall time: 0 ns</code> ?</p>