[jira] [Commented] (CALCITE-4432) When the RelNode's input is the same subset as the node belonged to, not choose this node as best.

[Julian Hyde (Jira)]

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https://issues.apache.org/jira/browse/CALCITE-4432?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17263099#comment-17263099
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Julian Hyde commented on CALCITE-4432:
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[~thomas.rebele], That seems reasonable. Since all 3 parts of the cost must be 
non-negative, the check should throw if {{parent cpu < child cpu}}, or if 
{{parent io < child io}}, or if {{parent rows < child rows}}. (That's slightly 
stronger than your suggestion, {{parent cost < child cost}}, because {{<}} is 
not a total order.)

> When the RelNode's input is the same subset as the node belonged to, not 
> choose this node as best.
> --------------------------------------------------------------------------------------------------
>
>                 Key: CALCITE-4432
>                 URL: https://issues.apache.org/jira/browse/CALCITE-4432
>             Project: Calcite
>          Issue Type: Bug
>          Components: core
>            Reporter: Ziwei Liu
>            Assignee: Ziwei Liu
>            Priority: Major
>
> If a subset have a cyclic node, the node's input is this subset itself. If 
> the beset 



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