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https://issues.apache.org/jira/browse/SPARK-18376?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15649779#comment-15649779
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Apache Spark commented on SPARK-18376:
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User 'viirya' has created a pull request for this issue:
https://github.com/apache/spark/pull/15824
> Skip subexpression elimination for conditional expressions
> ----------------------------------------------------------
>
> Key: SPARK-18376
> URL: https://issues.apache.org/jira/browse/SPARK-18376
> Project: Spark
> Issue Type: Bug
> Components: SQL
> Reporter: Liang-Chi Hsieh
>
> We should disallow subexpression elimination for expressions wrapped in
> conditional expressions such as {{If}}.
> Because for an example like this:
> {code}
> if (isNull(subexpr)) {
> ...
> } else {
> AssertNotNull(subexpr) // subexpr2
> ....
> SomeExpr(AssertNotNull(subexpr)) // SomeExpr(subexpr2)
> }
> {code}
> AssertNotNull(subexpr) will be recognized as a subexpression and evaluate
> even the else branch is never run. Under such cases, it possibly causes not
> excepted exception and performance regression.
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