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https://issues.apache.org/jira/browse/CALCITE-4350?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17220442#comment-17220442
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Liya Fan commented on CALCITE-4350:
-----------------------------------
[~julianhyde] Thanks a lot for your feedback. I have prepared a PR which should
be simple and easy to review (I think).
> The reverse operation of collation direction is overly relaxed
> --------------------------------------------------------------
>
> Key: CALCITE-4350
> URL: https://issues.apache.org/jira/browse/CALCITE-4350
> Project: Calcite
> Issue Type: Improvement
> Components: core
> Reporter: Liya Fan
> Assignee: Liya Fan
> Priority: Major
> Labels: pull-request-available
> Fix For: 1.27.0
>
> Time Spent: 10m
> Remaining Estimate: 0h
>
> For the current implementation, {{RelFieldCollation#Direction#reverse}}
> returns \{{DESCENDING}} for \{{STRICTLY_ASCENDING}}, and returns
> \{{ASCENDING}} for {{STRICTLY_DESCENDING}}.
> This is overly relaxed. In a strict manner, it should return
> \{{STRICTLY_DESCENDING}} for \{{STRICTLY_ASCENDING}}, and vice versa.
> If the user needs to get the relaxed reverse direction, they may call
> \{{collation.getDirection().reverse().lax();}}, as in many places of our code
> base.
> Do you agree?
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