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https://issues.apache.org/jira/browse/CALCITE-4160?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17173945#comment-17173945
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Julian Hyde commented on CALCITE-4160:
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I am against a global config option because it affects all users of the system,
and it makes the system more difficult for developers to
understand/debug/configure.
I don't see a hint as much of an inconvenience to the users. The users are
already adding {{ORDER BY}} into their sub-queries, which is non-standard, and
in my opinion does not belong in SQL. (BigData systems have a history of adding
bringing physical considerations into what is otherwise a logical language.
Consider for example [Hive's CLUSTER BY and DISTRIBUTE BY
clauses|https://www.tutorialspoint.com/hive/hiveql_select_where.htm]. Those
extensions are a mistake.)
It seems to me that allowing {{ORDER BY}} in sub-queries but ignoring it unless
the hint is present is a good compromise.
If you want to achieve this via configuration, add a flag to the particular
component's configuration. Probably {{SqlToRelConverter.Config}}, since this is
probably where the {{ORDER BY}} gets removed. But not a global config flag.
> Add configuration to retain ORDER BY in sub-query
> -------------------------------------------------
>
> Key: CALCITE-4160
> URL: https://issues.apache.org/jira/browse/CALCITE-4160
> Project: Calcite
> Issue Type: Improvement
> Components: core
> Reporter: Jiatao Tao
> Assignee: Jiatao Tao
> Priority: Minor
> Attachments: image-2020-08-07-10-48-59-599.png,
> image-2020-08-07-10-50-22-351.png
>
>
> Pre discussion see in
> https://issues.apache.org/jira/browse/CALCITE-2798
> https://issues.apache.org/jira/browse/CALCITE-3664
> IMO, we should at least provide a configuration about this. People use
> Calcite most for its optimizer, and this info users may care, How it executed
> is by the engine, but users should know this in the plan.
>
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