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https://issues.apache.org/jira/browse/CALCITE-3851?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17060546#comment-17060546
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Julian Hyde commented on CALCITE-3851:
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I wish we didn't have {{replaceInput}}. Things not being perfect is not an
argument for making them worse.
{{String.hash}} doesn't seem comparable - it does not affect the observable
behavior of a {{String}} object.
Regarding the semantics of "prune". If a RelNode is pruned, it means 'there is
a {{RelNode}} in this planner that is equivalent to it and incontrovertibly
better'. That definition relies on the set of nodes in a particular planner. It
is not a universal property of the {{RelNode}}.
> Replace the node importance map with a set for pruned nodes
> -----------------------------------------------------------
>
> Key: CALCITE-3851
> URL: https://issues.apache.org/jira/browse/CALCITE-3851
> Project: Calcite
> Issue Type: Improvement
> Components: core
> Reporter: Liya Fan
> Priority: Minor
> Labels: pull-request-available
> Time Spent: 1h 40m
> Remaining Estimate: 0h
>
> Currently, volcano planner stores rel node importances with a map. In fact,
> the value of the map can only be 0.
> So there is no need to store the values, and we replace the map with a set to
> store nodes whose importances are 0.
> This makes the code logic clearer, and avoids instability caused by comparing
> floating point values.
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