Github user HyukjinKwon commented on a diff in the pull request:
https://github.com/apache/spark/pull/13155#discussion_r63626483
--- Diff: sql/core/src/test/scala/org/apache/spark/sql/SubquerySuite.scala
---
@@ -293,4 +293,65 @@ class SubquerySuite extends QueryTest with
SharedSQLContext {
""".stripMargin),
Row(3) :: Nil)
}
+
+ test("COUNT bug in WHERE clause (Filter)") {
+
+ // Case 1: Canonical example of the COUNT bug
+ checkAnswer(
+ sql("select l.a from l where (select count(*) from r where l.a =
r.c) < l.a"),
+ Row(1) :: Row(1) :: Row(3) :: Row(6) :: Nil)
+
+ // Case 2: count(*) = 0; could be rewritten to NOT EXISTS but
currently uses
+ // a rewrite that is vulnerable to the COUNT bug
+ checkAnswer(
+ sql("select l.a from l where (select count(*) from r where l.a =
r.c) = 0"),
+ Row(1) :: Row(1) :: Row(null) :: Row(null) :: Nil)
+
+ // Case 3: COUNT bug without a COUNT aggregate
+ checkAnswer(
+ sql("select l.a from l where (select sum(r.d) is null from r where
l.a = r.c)"),
+ Row(1) :: Row(1) ::Row(null) :: Row(null) :: Row(6) :: Nil)
+
--- End diff --
(Maybe remove these blank lines,
https://github.com/databricks/scala-style-guide#blanklines)
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