Github user cloud-fan commented on a diff in the pull request:
https://github.com/apache/spark/pull/9308#discussion_r43369777
--- Diff: sql/core/src/test/scala/org/apache/spark/sql/SQLQuerySuite.scala
---
@@ -1870,4 +1870,19 @@ class SQLQuerySuite extends QueryTest with
SharedSQLContext {
assert(sampled.count() == sampledOdd.count() + sampledEven.count())
}
}
+
+ test("SPARK-10707: nullability should be correctly propagated through
set operations") {
+ withTempTable("src") {
+ Seq((1, 1)).toDF("key", "value").registerTempTable("src")
+ checkAnswer(
+ sql("""SELECT count(v) FROM (
+ | SELECT v FROM (
+ | SELECT 'foo' AS v FROM src UNION ALL
+ | SELECT NULL AS v FROM src
+ | ) my_union WHERE isnull(v)
+ |) my_subview""".stripMargin),
+ Seq(Row(0)))
--- End diff --
This test doesn't look clear to me, how about:
```
checkAnswer(
sql(
"""
|SELECT a FROM (
| SELECT ISNULL(v) AS a, RAND() FROM (
| SELECT 'foo' AS v UNION ALL SELECT null AS v
| ) my_union
|) my_view
""".stripMargin),
Row(false) :: Row(true) :: Nil)
```
Use `RAND()` to stop column pruning for `Union` and then we can show that
`isnull(v)` is wrong because of the wrong nullability of `Union` output.
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