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https://issues.apache.org/jira/browse/CALCITE-2798?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Julian Hyde resolved CALCITE-2798.
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Resolution: Fixed
Fix Version/s: 1.19.0
Fixed in
[cf363b5989d35bd8b4d5f14c7a99acea6e9f0f5a|https://gitbox.apache.org/repos/asf?p=calcite.git;a=commit;h=cf363b5989d35bd8b4d5f14c7a99acea6e9f0f5a].
Thanks for the PR, [~hyuan]!
> Optimizer should remove ORDER BY in sub-query, provided it has no LIMIT or
> OFFSET
> ---------------------------------------------------------------------------------
>
> 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
> Priority: Major
> Fix For: 1.19.0
>
>
> 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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