[jira] [Commented] (CALCITE-5715) Prune old nodes after projection merging in ProjectionMergeRule

["Benchao Li (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CALCITE-5715?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17724251#comment-17724251 ] 

Benchao Li commented on CALCITE-5715:
-------------------------------------

All existing tests pass after this change: https://github.com/apache/calcite/pull/3216

> Prune old nodes after projection merging in ProjectionMergeRule
> ---------------------------------------------------------------
>
>                 Key: CALCITE-5715
>                 URL: https://issues.apache.org/jira/browse/CALCITE-5715
>             Project: Calcite
>          Issue Type: Improvement
>          Components: core
>    Affects Versions: 1.34.0
>            Reporter: Benchao Li
>            Priority: Major
>
> We already have many similar usages (prune old nodes) to reduce the search scope, I propose to also add this for {{ProjectionMergeRule}}. Do you have any concerns about this?
> The reason I propose to do this optimization for {{ProjectionMergeRule}} is that I met a problem that two sets will point to each other after projection merging, and the planner will run into dead loop. (It's hard to show the details, I haven't got a simple reproducible demo yet)



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