title: Lost calculated fields
body: <p>I am using Amazon Quicksight for some data analysis and visualisation. </p>
  
  <p>I wanted to extend existing data with a new table in datasource view -> add data link. after joining this new table with existing one, data refresh and switching to data analysis i realised that i have lost all calculated fields i had in my project. So now i have following questions:</p>
  
  <ol>
  <li>Anyone else encountered similar issue?</li>
  <li>Is it possible to recover lost fields? </li>
  <li>is it possible to go back to a state before change was done? It seems that Undo option does not work for changes done in data sets</li>
  <li>how to protect my analysis against such unexpected behaviours in future?</li>
  </ol>