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From "Zoltan Haindrich (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HIVE-21152) Rewrite if expression to case and recognize simple case as an if
Date Mon, 04 Mar 2019 17:07:00 GMT

     [ https://issues.apache.org/jira/browse/HIVE-21152?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Zoltan Haindrich updated HIVE-21152:
------------------------------------
    Attachment: HIVE-21152.04.patch

> Rewrite if expression to case and recognize simple case as an if
> ----------------------------------------------------------------
>
>                 Key: HIVE-21152
>                 URL: https://issues.apache.org/jira/browse/HIVE-21152
>             Project: Hive
>          Issue Type: Improvement
>          Components: CBO
>            Reporter: Zoltan Haindrich
>            Assignee: Zoltan Haindrich
>            Priority: Major
>         Attachments: HIVE-21152.01.patch, HIVE-21152.02.patch, HIVE-21152.03.patch, HIVE-21152.04.patch
>
>
> * {{IF}} is not part of the sql standard; however given its special form its simpler
- and currently in Hive it also has vectorized support
> * people writing standard sql may write: {{CASE WHEN member=1 THEN attr+1 else attr+2
END}} which is essentially an if.
> The idea is to rewrite IFs to CASEs for the cbo; and recognize simple "CASE"-s as IFs
to get vectorization on them if possible



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