kings129 opened a new pull request, #40858: URL: https://github.com/apache/spark/pull/40858
… value for unmatched row ### What changes were proposed in this pull request? When doing an outer join with joinWith on DataFrames, unmatched rows return Row objects with null fields instead of a single null value. This is not a expected behavior, and it's a regression introduced in [this commit](https://github.com/apache/spark/commit/cd92f25be5a221e0d4618925f7bc9dfd3bb8cb59). This pull request aims to fix the regression, note this is not a full rollback of the commit, do not add back "schema" variable. ``` case class ClassData(a: String, b: Int) val left = Seq(ClassData("a", 1), ClassData("b", 2)).toDF val right = Seq(ClassData("x", 2), ClassData("y", 3)).toDF left.joinWith(right, left("b") === right("b"), "left_outer").collect ``` ``` Wrong results (current behavior): Array(([a,1],[null,null]), ([b,2],[x,2])) Correct results: Array(([a,1],null), ([b,2],[x,2])) ``` ### Why are the changes needed? We need to address the regression mentioned above. It results in unexpected behavior changes in the Dataframe joinWith API between versions 2.4.8 and 3.0.0+. This could potentially cause data correctness issues for users who expect the old behavior when using Spark 3.0.0+. ### Does this PR introduce _any_ user-facing change? No ### How was this patch tested? Added unit test (use the same test in previous [closed pull request](https://github.com/apache/spark/pull/35140), credit to Clément de Groc) Run sql-core and sql-catalyst submodules locally with ./build/mvn clean package -pl sql/core,sql/catalyst Closes #40755 from kings129/encoder_bug_fix. Authored-by: --global <[email protected]> <!-- Thanks for sending a pull request! Here are some tips for you: 1. If this is your first time, please read our contributor guidelines: https://spark.apache.org/contributing.html 2. Ensure you have added or run the appropriate tests for your PR: https://spark.apache.org/developer-tools.html 3. 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