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https://issues.apache.org/jira/browse/SPARK-19017?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15799055#comment-15799055
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Nattavut Sutyanyong commented on SPARK-19017:
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I think we both agree that the result of the expression {{(2, 1) = (2, null)}}
is unknown (null). It is the negation of this expression that is the centre of
this discussion.
If {{a = (2, 1)}} and {{b = (1, null)}}, what is the semantics of {{a <> b}}?
You have suggested two formulas
{{not(a.x1 = b.x1 and a.x2 = b.x2)}}
and
{{a.x1 <> b.x1 or a.x2 <> b.x2}}
Would you agree that these two formulas are equivalent? The second formula is
just the result of applying De Morgan's laws on the first formula, i.e., {{not
(x and y) == (not x) or (not y)}}.
How does Spark evaluate the formulas today? Here is my test:
{code}
scala> Seq(1).toDF("t1a").createOrReplaceTempView("t1")
scala> sql("select t1a from t1").show
+---+
|t1a|
+---+
| 1|
+---+
scala> sql("select t1a from t1 where not (2=1 and 1=null)").show
+---+
|t1a|
+---+
| 1|
+---+
scala> sql("select t1a from t1 where 2<>1 or 1<>null").show
+---+
|t1a|
+---+
| 1|
+---+
{code}
> NOT IN subquery with more than one column may return incorrect results
> ----------------------------------------------------------------------
>
> Key: SPARK-19017
> URL: https://issues.apache.org/jira/browse/SPARK-19017
> Project: Spark
> Issue Type: Bug
> Components: SQL
> Affects Versions: 2.0.0, 2.0.1, 2.0.2, 2.1.0
> Reporter: Nattavut Sutyanyong
>
> When putting more than one column in the NOT IN, the query may not return
> correctly if there is a null data. We can demonstrate the problem with the
> following data set and query:
> {code}
> Seq((2,1)).toDF("a1","b1").createOrReplaceTempView("t1")
> Seq[(java.lang.Integer,java.lang.Integer)]((1,null)).toDF("a2","b2").createOrReplaceTempView("t2")
> sql("select * from t1 where (a1,b1) not in (select a2,b2 from t2)").show
> +---+---+
> | a1| b1|
> +---+---+
> +---+---+
> {code}
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