[jira] [Created] (CALCITE-4021) EnumerableUnion should preserve ordering when all inputs have the same collation

[Rui Wang (Jira)]

Rui Wang created CALCITE-4021:
---------------------------------

             Summary: EnumerableUnion should preserve ordering when all inputs 
have the same collation
                 Key: CALCITE-4021
                 URL: https://issues.apache.org/jira/browse/CALCITE-4021
             Project: Calcite
          Issue Type: Improvement
            Reporter: Rui Wang


For query:

"select name from sales_dept
union 
select name from it_dept
order by mgr"

We could generate a plan based on 
https://issues.apache.org/jira/browse/CALCITE-4017:

{code:java}
EnumerableUnion
    EnumerableProject
        EnumerableSort
           EnumerableTableScan[name="sales_dept"]
    EnumerableProject
        EnumerableSort
           EnumerableTableScan[name="it_dept"]
{code}

So EnumerableUnion should preserve ordering when all input have the same 
collation to make sure result of query is correct.





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