Find minimum for a timestamp through Spark groupBy dataframe
<p>When I try to group my dataframe on a column then try to find the minimum for each grouping <code>groupbyDatafram.min('timestampCol')</code> it appears I cannot do it on non numerical columns. Then how can I properly filter the minimum (earliest) date on the groupby? </p>

<p>I am streaming the dataframe from a postgresql S3 instance, so that data is already configured. </p>