GitHub user gatorsmile opened a pull request: https://github.com/apache/spark/pull/15781
[SPARK-17981] [SPARK-17957] [SQL] [BACKPORT-2.0] Fix Incorrect Nullability Setting to False in FilterExec ### What changes were proposed in this pull request? **This PR is to backport the fix https://github.com/apache/spark/pull/15523 to 2.0.** 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, ``` Scala 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 https://github.com/gatorsmile/spark nullabilityFix Alternatively you can review and apply these changes as the patch at: https://github.com/apache/spark/pull/15781.patch To close this pull request, make a commit to your master/trunk branch with (at least) the following in the commit message: This closes #15781 ---- commit f2254619c96b95156c0cb79ef8f70330cab7ba1d Author: gatorsmile <gatorsm...@gmail.com> Date: 2016-11-05T05:50:27Z fix. ---- --- If your project is set up for it, you can reply to this email and have your reply appear on GitHub as well. If your project does not have this feature enabled and wishes so, or if the feature is enabled but not working, please contact infrastructure at infrastruct...@apache.org or file a JIRA ticket with INFRA. --- --------------------------------------------------------------------- To unsubscribe, e-mail: reviews-unsubscr...@spark.apache.org For additional commands, e-mail: reviews-h...@spark.apache.org