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https://issues.apache.org/jira/browse/HIVE-12809?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15106071#comment-15106071
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Gopal V commented on HIVE-12809:
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Yes, two invariants.
If any column has noNulls, the final output has no Nulls
If first column is non-null & repeating, the final output is the first column +
isRepeating retained.
> Vectorization: fast-path for coalesce if input.noNulls = true
> -------------------------------------------------------------
>
> Key: HIVE-12809
> URL: https://issues.apache.org/jira/browse/HIVE-12809
> Project: Hive
> Issue Type: Bug
> Affects Versions: 2.0.0, 2.1.0
> Reporter: Gopal V
> Assignee: Gopal V
> Attachments: HIVE-12809.1.patch, HIVE-12809.2.patch
>
>
> Coalesce can skip processing other columns, if all the input columns are
> non-null.
> Possibly retaining, isRepeating=true.
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