[GitHub] [calcite] vineetgarg02 commented on issue #1087: [CALCITE-1172] Add rule to flatten two Aggregate operators into one

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vineetgarg02 commented on issue #1087: [CALCITE-1172] Add rule to flatten two Aggregate operators into one
URL: https://github.com/apache/calcite/pull/1087#issuecomment-470800554
 
 
   @hsyuan  Following query on an empty table should produce NULL
   `select sum(y) from (
           select ename, count(mgr) y from 
           sales.emp group by ename, mgr) t`
   But with this rule I believe this will be rewritten to
   `select count(y) from t` which will produce 0.
   Can you add a test case for this and verify?
   
   Other similar query is:
   `select sum(y) from (
           select ename, mgr, count(mgr) y from 
           sales.emp group by ename, mgr) t 
           group by cube(ename, mgr);`
   
   This one should also output one row - NULL.
   
   
   

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