[SPARK-19933][SQL] Do not change output of a subquery

## What changes were proposed in this pull request?
The `RemoveRedundantAlias` rule can change the output attributes (the expression id's to be precise) of a query by eliminating the redundant alias producing them. This is no problem for a regular query, but can cause problems for correlated subqueries: The attributes produced by the subquery are used in the parent plan; changing them will break the parent plan.

This PR fixes this by wrapping a subquery in a `Subquery` top level node when it gets optimized. The `RemoveRedundantAlias` rule now recognizes `Subquery` and makes sure that the output attributes of the `Subquery` node are retained.

## How was this patch tested?
Added a test case to `RemoveRedundantAliasAndProjectSuite` and added a regression test to `SubquerySuite`.

Author: Herman van Hovell <hvanhovell@databricks.com>

Closes #17278 from hvanhovell/SPARK-19933.

1 files changed, 14 insertions, 0 deletions

diff --git a/sql/core/src/test/scala/org/apache/spark/sql/SubquerySuite.scala b/sql/core/src/test/scala/org/apache/spark/sql/SubquerySuite.scala
index 6f1cd49c08..5fe6667cec 100644
--- a/sql/core/src/test/scala/org/apache/spark/sql/SubquerySuite.scala
+++ b/sql/core/src/test/scala/org/apache/spark/sql/SubquerySuite.scala
@@ -830,4 +830,18 @@ class SubquerySuite extends QueryTest with SharedSQLContext {
         Row(1) :: Row(0) :: Nil)
     }
   }
+
+  test("SPARK-19933 Do not eliminate top-level aliases in sub-queries") {
+    withTempView("t1", "t2") {
+      spark.range(4).createOrReplaceTempView("t1")
+      checkAnswer(
+        sql("select * from t1 where id in (select id as id from t1)"),
+        Row(0) :: Row(1) :: Row(2) :: Row(3) :: Nil)
+
+      spark.range(2).createOrReplaceTempView("t2")
+      checkAnswer(
+        sql("select * from t1 where id in (select id as id from t2)"),
+        Row(0) :: Row(1) :: Nil)
+    }
+  }
 }