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

["Jinpeng Wu (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CALCITE-4432?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17247170#comment-17247170 ] 

Jinpeng Wu commented on CALCITE-4432:
-------------------------------------

For example, there is a RelSubset A with best as X. RelSubset B with best Y is the input subset of X. When A is merged with B, A's best should be replaced by Y as X's cost should always greater than Y's cost.  

This bug is fired when X's cost is not greater than Y's cost. 

There are all kinds of reason why Y's cost is not always larger than X's cost. For example, X's selfCost is underflowed or X's totalCost is overflowed. 

But these should be the issue of cost model, not calcite core. 

 

> 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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