[jira] [Created] (SPARK-8636) CaseKeyWhen has incorrect NULL handling

["Santiago M. Mola (JIRA)" <ji...@apache.org>]

Santiago M. Mola created SPARK-8636:
---------------------------------------

             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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