[jira] [Created] (CALCITE-2798) Optimizer should remove unneeded Sort

["Vladimir Sitnikov (JIRA)" <ji...@apache.org>]

Vladimir Sitnikov created CALCITE-2798:
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             Summary: Optimizer should remove unneeded Sort
                 Key: CALCITE-2798
                 URL: https://issues.apache.org/jira/browse/CALCITE-2798
             Project: Calcite
          Issue Type: Improvement
          Components: core
    Affects Versions: 1.18.0
            Reporter: Vladimir Sitnikov
            Assignee: Julian Hyde


The following SQL performs sort twice, however inner sort can be eliminated
{code}select * from (
  select * from "emps" 
order by "emps"."deptno"
) order by 1 desc{code}

The same goes for (window calculation will sort on its own)

{code}select row_number() over (order by "emps"."deptno")  from (
  select * from "emps" 
order by "emps"."deptno" desc
){code}

The same goes for SetOp (union, minus):
{code}select * from (
  select * from "emps" 
order by "emps"."deptno"
) union select * from (
  select * from "emps" 
order by "emps"."deptno" desc
){code}

There might be other cases like that (e.g. Aggregate, Join, Exchange, SortExchange)



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