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https://issues.apache.org/jira/browse/HIVE-16731?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Teddy Choi updated HIVE-16731:
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Attachment: HIVE-16731.1.patch
The existing implementation handled only one simple case. It's two of columns
or non-null constants, such as "CASE WHEN bool1 THEN column1 ELSE value1 END".
It's easy to translate into an equivalent IF expression, "IF(bool1, column1,
value1)". So I made it to handle multiple WHEN clauses and an optional ELSE
clause with a recursive method.
Null values are common in WHEN clauses, but they are excluded in vectorization
process. So I made IfNullColumn and IfColumnNull classes to support them. It's
hard to include the classes in VectorizedExpressions annotation in GenericUDFIf
class, because description treats void as a member of integer family, which is
already existing one. But it's possible to handle them in
VectorizedContext.getIfExpression.
> Vectorization: Make "CASE WHEN (day_name='Sunday') THEN column1 ELSE null
> end" that involves a column name or expression THEN or ELSE vectorize
> -----------------------------------------------------------------------------------------------------------------------------------------------
>
> Key: HIVE-16731
> URL: https://issues.apache.org/jira/browse/HIVE-16731
> Project: Hive
> Issue Type: Bug
> Reporter: Matt McCline
> Assignee: Teddy Choi
> Priority: Critical
> Attachments: HIVE-16731.1.patch
>
>
> Currently, CASE WHEN statements like that become VectorUDFAdaptor expressions.
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