GitHub user gatorsmile opened a pull request:

    [SPARK-17981] [SPARK-17957] [SQL] Incorrectly Set Nullability to False in 

    ### What changes were proposed in this pull request?
    When `FilterExec` contains `isNotNull`, which could be inferred and pushed 
down or users specified, we convert the nullability of the involved columns if 
the top-layer expression is null-intolerant. However, this is not correct, if 
the top-layer expression is not a leaf expression, it could still tolerate the 
null when it has null-tolerant child expressions. 
    For example, `cast(coalesce(a#5, a#15) as double)`. Although `cast` is a 
null-intolerant expression, but obviously` coalesce` is null-tolerant. Thus, it 
could eat null.
    When the nullability is wrong, we could generate incorrect results in 
different cases. For example, 
        val df1 = Seq((1, 2), (2, 3)).toDF("a", "b")
        val df2 = Seq((2, 5), (3, 4)).toDF("a", "c")
        val joinedDf = df1.join(df2, Seq("a"), "outer").na.fill(0)
        val df3 = Seq((3, 1)).toDF("a", "d")
        joinedDf.join(df3, "a").show
    The optimized plan is like 
    Project [a#29, b#30, c#31, d#42]
    +- Join Inner, (a#29 = a#41)
       :- Project [cast(coalesce(cast(coalesce(a#5, a#15) as double), 0.0) as 
int) AS a#29, cast(coalesce(cast(b#6 as double), 0.0) as int) AS b#30, 
cast(coalesce(cast(c#16 as double), 0.0) as int) AS c#31]
       :  +- Filter isnotnull(cast(coalesce(cast(coalesce(a#5, a#15) as 
double), 0.0) as int))
       :     +- Join FullOuter, (a#5 = a#15)
       :        :- LocalRelation [a#5, b#6]
       :        +- LocalRelation [a#15, c#16]
       +- LocalRelation [a#41, d#42]
    Without the fix, it returns an empty result. With the fix, it can return a 
correct answer:
    |  a|  b|  c|  d|
    |  3|  0|  4|  1|
    ### How was this patch tested?
    Added test cases to verify the nullability changes in FilterExec. Also 
added a test case for verifying the reported incorrect result.

You can merge this pull request into a Git repository by running:

    $ git pull nullabilityFilterExec

Alternatively you can review and apply these changes as the patch at:

To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:

    This closes #15523
commit 54c3cc849e91b9bedc6379e04edc9e23245be760
Author: gatorsmile <>
Date:   2016-10-17T23:29:43Z



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