[GitHub] [arrow-datafusion] alamb commented on issue #110: Grouping by column position

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alamb commented on issue #110:
URL: https://github.com/apache/arrow-datafusion/issues/110#issuecomment-826831247


   Comment from Jorge Leitão(jorgecarleitao) @ 2020-10-23T06:03:45.335+0000:
   <pre>Could you describe what is the use-case? E.g. in which situation does that improve readability over the having the column name, or in which case does the column name not work?</pre>
   
   Comment from Pavel Tiunov(paveltiunov) @ 2020-10-23T06:41:53.205+0000:
   <pre>Hey [~jorgecarleitao]! Thanks for the quick turnaround. The use case is usually to support grouping by complex expressions. For example
   {code:java}
   SELECT date_trunc(convert_tz(`page_views__time_hour`, 'America/Los_Angeles'), 'week') `page_views__time_week`, sum(`page_views__count`) `page_views__count` FROM page_views GROUP BY date_trunc(convert_tz(`page_views__time_hour`, 'America/Los_Angeles'), 'week') LIMIT 10000
   {code}
   becomes
   {code:java}
   SELECT date_trunc(convert_tz(`page_views__time_hour`, 'America/Los_Angeles'), 'week') `page_views__time_week`, sum(`page_views__count`) `page_views__count` FROM page_views GROUP BY 1 LIMIT 10000
   {code}
   Calculated columns can be pretty complex and it usually just bloats up the SQL significantly. I believe it's beneficial to have this feature as most of the modern query engines have it.</pre>
   
   Comment from Jorge Leitão(jorgecarleitao) @ 2020-10-23T08:00:39.544+0000:
   <pre>Thanks for the example, [~paveltiunov] . makes sense
   
   Meanwhile, I think that you can use <{{expression> AS name}} and {{GROUP BY name}} .
   
    </pre>


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