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https://issues.apache.org/jira/browse/CALCITE-4514?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17292537#comment-17292537
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Botong Huang commented on CALCITE-4514:
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Hi [~julianhyde], I just noticed some minor issues. For instance in
_isSmaller()_, when _set1.parents.size() > set2.parents.size()_, we should
return false rather than fall back to relset size and id.
We need this additional patch:
[https://github.com/apache/calcite/compare/master...hbtoo:CALCITE-4514]
> [CALCITE-4514] Fine tune the merge order of two RelSets
> -------------------------------------------------------
>
> Key: CALCITE-4514
> URL: https://issues.apache.org/jira/browse/CALCITE-4514
> Project: Calcite
> Issue Type: Improvement
> Reporter: Botong Huang
> Priority: Minor
> Labels: pull-request-available
> Fix For: 1.27.0
>
> Time Spent: 40m
> Remaining Estimate: 0h
>
> When merging two relsets, we have two preferences:
> 1. Merge parent relset into child relset
> 2. Merge newer relset into older relset
> Currently, when the two relsets are parent set of each other, we randomly
> pick a merge order without checking the second condition above. For
> performance reasons, we should, to avoid unnecessary churn.
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