<p dir="auto">Superset returns an internal server error when there are duplicated calculated column names</p>
<h3 dir="auto">Expected results</h3>
<p dir="auto">No 5xx</p>
<h3 dir="auto">Actual results</h3>
<p dir="auto">5xx</p>
<h4 dir="auto">Screenshots</h4>
<p dir="auto"><a target="_blank" rel="noopener noreferrer nofollow" href="https://user-images.githubusercontent.com/7409244/69683280-22391c00-1069-11ea-9331-11bad441b29a.png"><img src="https://user-images.githubusercontent.com/7409244/69683280-22391c00-1069-11ea-9331-11bad441b29a.png" alt="image" style="max-width: 100%;"></a></p>
<h4 dir="auto">How to reproduce the bug</h4>
<p dir="auto">While recently creating a new set of calculated columns I forgot to change the name from the default of  for all the fields. While attempting to save this, I wound up getting an internal server error on the front end which mapped to a "Duplicate entry '-77284' for key 'uq_table_columns_column_name'" internally.</p>
<p dir="auto">It would be nice if that exception was caught or a specific error message surfaced so that people knew what they did wrong.</p>
<h3 dir="auto">Environment</h3>
<ul dir="auto">
<li>superset version: <code class="notranslate">master</code></li>
<li>python version: <code class="notranslate">3.6</code></li>
<li>node.js version: <code class="notranslate">8.6</code></li>
</ul>
<h3 dir="auto">Checklist</h3>
<p dir="auto">Make sure these boxes are checked before submitting your issue - thank you!</p>
<ul class="contains-task-list">
<li class="task-list-item"><input type="checkbox" id="" disabled="" class="task-list-item-checkbox" checked=""> I have checked the superset logs for python stacktraces and included it here as text if there are any.</li>
<li class="task-list-item"><input type="checkbox" id="" disabled="" class="task-list-item-checkbox" checked=""> I have reproduced the issue with at least the latest released version of superset.</li>
<li class="task-list-item"><input type="checkbox" id="" disabled="" class="task-list-item-checkbox" checked=""> I have checked the issue tracker for the same issue and I haven't found one similar.</li>
</ul>
<p dir="auto">Make sure these boxes are checked before submitting your issue - thank you!</p>
<ul class="contains-task-list">
<li class="task-list-item"><input type="checkbox" id="" disabled="" class="task-list-item-checkbox" checked=""> I have checked the superset logs for python stacktraces and included it here as text if any</li>
<li class="task-list-item"><input type="checkbox" id="" disabled="" class="task-list-item-checkbox" checked=""> I have reproduced the issue with at least the latest released version of superset</li>
<li class="task-list-item"><input type="checkbox" id="" disabled="" class="task-list-item-checkbox" checked=""> I have checked the issue tracker for the same issue and I haven't found one similar</li>
</ul>
<h3 dir="auto">Superset version</h3>
<p dir="auto">0.25.6</p>
<h3 dir="auto">Expected results</h3>
<p dir="auto">Expected result in 0.17.6 is :<br>
<a target="_blank" rel="noopener noreferrer nofollow" href="https://user-images.githubusercontent.com/30650330/41275495-ac6b8076-6e3e-11e8-8098-c642e79f6179.png"><img src="https://user-images.githubusercontent.com/30650330/41275495-ac6b8076-6e3e-11e8-8098-c642e79f6179.png" alt="image" style="max-width: 100%;"></a></p>
<h3 dir="auto">Actual results</h3>
<p dir="auto">Actual result which I am getting in 0.25.6 is :<br>
<a target="_blank" rel="noopener noreferrer nofollow" href="https://user-images.githubusercontent.com/30650330/41275520-cc665dba-6e3e-11e8-8f48-67fbc99b9a81.png"><img src="https://user-images.githubusercontent.com/30650330/41275520-cc665dba-6e3e-11e8-8f48-67fbc99b9a81.png" alt="image" style="max-width: 100%;"></a></p>
<h3 dir="auto">Steps to reproduce</h3>
<p dir="auto">Open the slice and select the table view.<br>
In the group by select any column with date as datatype<br>
select any metric against it.<br>
Output is epoch time against the metric</p>