[GitHub] gatorsmile commented on issue #23315: [SPARK-26366][SQL] ReplaceExceptWithFilter should consider NULL as False

[GitBox <gi...@apache.org>]

gatorsmile commented on issue #23315: [SPARK-26366][SQL] ReplaceExceptWithFilter should consider NULL as False
URL: https://github.com/apache/spark/pull/23315#issuecomment-447609414
 
 
   There is another bug in this rule. The condition of the right side must be deterministic; otherwise, the result could violate the definition of SQL compliant EXCEPT.  
   ```
    val df = Seq(1, 2, 2, 3).toDF("id")
   ```
   In the above example, if `df` is on the left side, the final result of EXCEPT will be either zero or two `2`. It is impossible to return a single 2 in the final result.

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