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https://issues.apache.org/jira/browse/SPARK-8636?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14605112#comment-14605112
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Animesh Baranawal commented on SPARK-8636:
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No a row with null will not be equal to another row with null if we follow the
modification. What do you say [~smolav] ?
> CaseKeyWhen has incorrect NULL handling
> ---------------------------------------
>
> Key: SPARK-8636
> URL: https://issues.apache.org/jira/browse/SPARK-8636
> Project: Spark
> Issue Type: Bug
> Components: SQL
> Affects Versions: 1.4.0
> Reporter: Santiago M. Mola
> Labels: starter
>
> CaseKeyWhen implementation in Spark uses the following equals implementation:
> {code}
> private def equalNullSafe(l: Any, r: Any) = {
> if (l == null && r == null) {
> true
> } else if (l == null || r == null) {
> false
> } else {
> l == r
> }
> }
> {code}
> Which is not correct, since in SQL, NULL is never equal to NULL (actually, it
> is not unequal either). In this case, a NULL value in a CASE WHEN expression
> should never match.
> For example, you can execute this in MySQL:
> {code}
> SELECT CASE NULL WHEN NULL THEN "NULL MATCHES" ELSE "NULL DOES NOT MATCH" END
> FROM DUAL;
> {code}
> And the result will be "NULL DOES NOT MATCH".
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