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https://issues.apache.org/jira/browse/HIVE-18819?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16379895#comment-16379895
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Matt McCline commented on HIVE-18819:
-------------------------------------
Because the new code is noticing non-column and non-scalar expressions -- in
other words: expressions that require computation -- those are considered
candidates for conditional IF statement vector expressions.
So, for example, some usages of IfExprStringScalarStringGroupColumn become
IfExprColumnCondExpr.
Is it worth generating more specialized versions of IfExprColumnCondExpr that
do outputColVector.setVal instead of outputColVector.setElement? Not clear it
is worth it for this round.
> Vectorization: Optimize IF statement expression evaluation of THEN/ELSE
> -----------------------------------------------------------------------
>
> Key: HIVE-18819
> URL: https://issues.apache.org/jira/browse/HIVE-18819
> Project: Hive
> Issue Type: Bug
> Components: Hive
> Affects Versions: 3.0.0
> Reporter: Matt McCline
> Assignee: Matt McCline
> Priority: Critical
> Attachments: HIVE-18819.01.patch
>
>
> Currently, all the rows of a batch are evaluated for the THEN and ELSE
> expressions even though only a value from one of them is needed for any
> particular row.
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