Github user gatorsmile commented on a diff in the pull request:
https://github.com/apache/spark/pull/19825#discussion_r153345990
--- Diff: sql/core/src/test/scala/org/apache/spark/sql/JoinSuite.scala ---
@@ -208,6 +208,21 @@ class JoinSuite extends QueryTest with
SharedSQLContext {
}
}
+ test("SPARK-22615: Empty relation child in left outer/right outer join
should pass" +
+ " Cartesian product check") {
+ val x = testData2.where($"a" === 2).as("x")
+ val y = testData2.where($"a" === 1 && !($"a" === 1)).as("y")
+ checkAnswer(x.join(y, Seq.empty, "left_outer"),
+ Row(2, 1, null, null) ::
+ Row(2, 2, null, null) :: Nil
+ )
+
+ checkAnswer(y.join(x, Seq.empty, "right_outer"),
+ Row(null, null, 2, 1) ::
+ Row(null, null, 2, 2) :: Nil
+ )
+ }
--- End diff --
The fix looks good to me. Instead of adding it here, to be safer, could you
write a suite `joinEmptyRelation.sql` in `SQLQueryTestSuite`? Then, we can
easily run all them against the other DBMS for ensuring the results are correct.
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