[jira] [Commented] (SPARK-2155) Support effectful / non-deterministic key expressions in CASE WHEN statements

["Reynold Xin (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/SPARK-2155?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14036992#comment-14036992 ] 

Reynold Xin commented on SPARK-2155:
------------------------------------

Can you include a link to some page that explains CASE KEY WHEN?

> Support effectful / non-deterministic key expressions in CASE WHEN statements
> -----------------------------------------------------------------------------
>
>                 Key: SPARK-2155
>                 URL: https://issues.apache.org/jira/browse/SPARK-2155
>             Project: Spark
>          Issue Type: Bug
>          Components: SQL
>            Reporter: Zongheng Yang
>            Priority: Minor
>
> Currently we translate CASE KEY WHEN to CASE WHEN, hence incurring redundant evaluations of the key expression. Relevant discussions here: https://github.com/apache/spark/pull/1055/files#r13784248
> If we are very in need of support for effectful key expressions, at least we can resort to the baseline approach of having both CaseWhen and CaseKeyWhen as expressions, which seem to introduce much code duplication (e.g. see https://github.com/concretevitamin/spark/blob/47d406a58d129e5bba68bfadf9dd1faa9054d834/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/predicates.scala#L216 for a sketch implementation). 



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