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https://issues.apache.org/jira/browse/HIVE-28196?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17849902#comment-17849902
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Seonggon Namgung commented on HIVE-28196:
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[~dkuzmenko] I created the PR to branch-4.0. Could you plrease review it? Thank
you.
> Preserve column stats when applying UDF upper/lower.
> ----------------------------------------------------
>
> Key: HIVE-28196
> URL: https://issues.apache.org/jira/browse/HIVE-28196
> Project: Hive
> Issue Type: Improvement
> Affects Versions: 4.0.0
> Reporter: Seonggon Namgung
> Assignee: Seonggon Namgung
> Priority: Major
> Labels: hive-4.0.1-must, performance, pull-request-available
> Fix For: 4.1.0
>
>
> Current Hive re-estimates column stats (including avgColLen) when it
> encounters UDF.
> In the case of upper and lower, Hive sets avgColLen to
> hive.stats.max.variable.length.
> But these UDFs do not change column stats and the default value(100) is too
> high for string type key columns, on which upper/lower are usually applied.
> This patch keeps input data's avgColLen after applying UDF upper/lower to
> make a better query plan.
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