[jira] [Commented] (HIVE-22913) HiveReduceExpressionsWithStatsRule should not invoke simplifcation during end of visits

["Zoltan Haindrich (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HIVE-22913?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17040750#comment-17040750 ] 

Zoltan Haindrich commented on HIVE-22913:
-----------------------------------------

not sure how much we gain from these simplification calls; possibly worth considering:
* A: only invoke simplification after the rule
* B: invoke simplification in case it makes a structural change; however in this case we still need to invoke it after the rule
* C: remove the simplification entirely; and add a new rule(SimplifyRule) which will only run simplification; put the existing ReduceExpressionRule and the new SimplifyRule in a RuleCollection

I'll explore A first

> HiveReduceExpressionsWithStatsRule should not invoke simplifcation during end of visits
> ---------------------------------------------------------------------------------------
>
>                 Key: HIVE-22913
>                 URL: https://issues.apache.org/jira/browse/HIVE-22913
>             Project: Hive
>          Issue Type: Improvement
>            Reporter: Zoltan Haindrich
>            Assignee: Zoltan Haindrich
>            Priority: Major
>
> * doing a simplification is a full visit of the subtree
> * in case the rule makes a structural change; it will invoke simplification during exiting the recursion
> https://github.com/apache/hive/blob/5012954396c98c94d0ff64fe3bbdb74e6077f190/ql/src/java/org/apache/hadoop/hive/ql/optimizer/calcite/rules/HiveReduceExpressionsWithStatsRule.java#L275



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