Santiago M. Mola created SPARK-8636:
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Summary: 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
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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