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https://issues.apache.org/jira/browse/SPARK-35449?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Adam Binford updated SPARK-35449:
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Description:
[https://github.com/apache/spark/pull/30245] added support for creating
subexpressions that are present in all branches of conditional statements.
However, for a statement to be in "all branches" of a CaseWhen statement, it
must also be in the elseValue. This can lead to a subexpression to be created
and run for branches of a conditional that don't pass. This can cause issues
especially with a UDF in a branch that gets executed assuming the condition is
true. For example:
{code:java}
val col = when($"id" < 0, myUdf($"id"))
spark.range(1).select(when(col > 0, col)).show()
{code}
myUdf($"id") gets extracted as a subexpression and executed even though both
conditions don't pass and it should never be executed.
> Should not extract common expressions from value expressions when elseValue
> is empty in CaseWhen
> ------------------------------------------------------------------------------------------------
>
> Key: SPARK-35449
> URL: https://issues.apache.org/jira/browse/SPARK-35449
> Project: Spark
> Issue Type: Sub-task
> Components: SQL
> Affects Versions: 3.2.0
> Reporter: L. C. Hsieh
> Priority: Major
>
> [https://github.com/apache/spark/pull/30245] added support for creating
> subexpressions that are present in all branches of conditional statements.
> However, for a statement to be in "all branches" of a CaseWhen statement, it
> must also be in the elseValue. This can lead to a subexpression to be created
> and run for branches of a conditional that don't pass. This can cause issues
> especially with a UDF in a branch that gets executed assuming the condition
> is true. For example:
> {code:java}
> val col = when($"id" < 0, myUdf($"id"))
> spark.range(1).select(when(col > 0, col)).show()
> {code}
> myUdf($"id") gets extracted as a subexpression and executed even though both
> conditions don't pass and it should never be executed.
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