Fixing issue in backtick handling for subquery aliases

Author: ravipesala

sql/hive/src/main/scala/org/apache/spark/sql/hive/HiveQl.scala

@@ -639,7 +639,7 @@ private[hive] object HiveQl {
   def nodeToRelation(node: Node): LogicalPlan = node match {
     case Token("TOK_SUBQUERY",
            query :: Token(alias, Nil) :: Nil) =>
-      Subquery(alias, nodeToPlan(query))
+      Subquery(cleanIdentifier(alias), nodeToPlan(query))
 
     case Token(laterViewToken(isOuter), selectClause :: relationClause :: Nil) =>
       val Token("TOK_SELECT",

sql/hive/src/test/scala/org/apache/spark/sql/hive/execution/SQLQuerySuite.scala

@@ -68,5 +68,11 @@ class SQLQuerySuite extends QueryTest {
     checkAnswer(
       sql("SELECT k FROM (SELECT `key` AS `k` FROM src) a"),
       sql("SELECT `key` FROM src").collect().toSeq)
-  }  
+  }
+
+  test("SPARK-3834 Backticks not correctly handled in subquery aliases") {
+    checkAnswer(
+      sql("SELECT a.key FROM (SELECT key FROM src) `a`"),
+      sql("SELECT `key` FROM src").collect().toSeq)
+  }
 }