[SPARK-13321][SQL] Support nested UNION in parser

JIRA: https://issues.apache.org/jira/browse/SPARK-13321

The following SQL can not be parsed with current parser:

    SELECT  `u_1`.`id` FROM (((SELECT  `t0`.`id` FROM `default`.`t0`) UNION ALL (SELECT  `t0`.`id` FROM `default`.`t0`)) UNION ALL (SELECT  `t0`.`id` FROM `default`.`t0`)) AS u_1

We should fix it.

Author: Liang-Chi Hsieh <viirya@gmail.com>

Closes #11204 from viirya/nested-union.

2 files changed, 84 insertions, 0 deletions

diff --git a/sql/catalyst/src/main/antlr3/org/apache/spark/sql/catalyst/parser/SparkSqlParser.g b/sql/catalyst/src/main/antlr3/org/apache/spark/sql/catalyst/parser/SparkSqlParser.g
index e1908a8e03..9aeea69cd2 100644
--- a/sql/catalyst/src/main/antlr3/org/apache/spark/sql/catalyst/parser/SparkSqlParser.g
+++ b/sql/catalyst/src/main/antlr3/org/apache/spark/sql/catalyst/parser/SparkSqlParser.g
@@ -2320,6 +2320,26 @@ regularBody[boolean topLevel]
    )
    |
    selectStatement[topLevel]
+   |
+   (LPAREN selectStatement0[true]) => nestedSetOpSelectStatement[topLevel]
+   ;
+
+nestedSetOpSelectStatement[boolean topLevel]
+   :
+   (
+   LPAREN s=selectStatement0[topLevel] RPAREN -> {$s.tree}
+   )
+   (set=setOpSelectStatement[$nestedSetOpSelectStatement.tree, topLevel])
+   -> {set == null}?
+      {$nestedSetOpSelectStatement.tree}
+   -> {$set.tree}
+   ;
+
+selectStatement0[boolean topLevel]
+   :
+   (selectStatement[true]) => selectStatement[topLevel]
+   |
+   (nestedSetOpSelectStatement[true]) => nestedSetOpSelectStatement[topLevel]
    ;
 
 selectStatement[boolean topLevel]
diff --git a/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/CatalystQlSuite.scala b/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/CatalystQlSuite.scala
index 42147f516f..1d1c0cb216 100644
--- a/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/CatalystQlSuite.scala
+++ b/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/CatalystQlSuite.scala
@@ -203,6 +203,70 @@ class CatalystQlSuite extends PlanTest {
       "from windowData")
   }
 
+  test("nesting UNION") {
+    val parsed = parser.parsePlan(
+      """
+       |SELECT  `u_1`.`id` FROM (((SELECT  `t0`.`id` FROM `default`.`t0`)
+       |UNION ALL (SELECT  `t0`.`id` FROM `default`.`t0`)) UNION ALL
+       |(SELECT  `t0`.`id` FROM `default`.`t0`)) AS u_1
+      """.stripMargin)
+
+    val expected = Project(
+      UnresolvedAlias(UnresolvedAttribute("u_1.id"), None) :: Nil,
+      Subquery("u_1",
+        Union(
+          Union(
+            Project(
+              UnresolvedAlias(UnresolvedAttribute("t0.id"), None) :: Nil,
+              UnresolvedRelation(TableIdentifier("t0", Some("default")), None)),
+            Project(
+              UnresolvedAlias(UnresolvedAttribute("t0.id"), None) :: Nil,
+              UnresolvedRelation(TableIdentifier("t0", Some("default")), None))),
+          Project(
+            UnresolvedAlias(UnresolvedAttribute("t0.id"), None) :: Nil,
+            UnresolvedRelation(TableIdentifier("t0", Some("default")), None)))))
+
+    comparePlans(parsed, expected)
+
+    val parsedSame = parser.parsePlan(
+      """
+       |SELECT  `u_1`.`id` FROM ((SELECT  `t0`.`id` FROM `default`.`t0`)
+       |UNION ALL (SELECT  `t0`.`id` FROM `default`.`t0`) UNION ALL
+       |(SELECT  `t0`.`id` FROM `default`.`t0`)) AS u_1
+      """.stripMargin)
+
+    comparePlans(parsedSame, expected)
+
+    val parsed2 = parser.parsePlan(
+      """
+       |SELECT  `u_1`.`id` FROM ((((SELECT  `t0`.`id` FROM `default`.`t0`)
+       |UNION ALL (SELECT  `t0`.`id` FROM `default`.`t0`)) UNION ALL
+       |(SELECT  `t0`.`id` FROM `default`.`t0`))
+       |UNION ALL (SELECT  `t0`.`id` FROM `default`.`t0`)) AS u_1
+      """.stripMargin)
+
+    val expected2 = Project(
+      UnresolvedAlias(UnresolvedAttribute("u_1.id"), None) :: Nil,
+      Subquery("u_1",
+        Union(
+          Union(
+            Union(
+              Project(
+                UnresolvedAlias(UnresolvedAttribute("t0.id"), None) :: Nil,
+                UnresolvedRelation(TableIdentifier("t0", Some("default")), None)),
+              Project(
+                UnresolvedAlias(UnresolvedAttribute("t0.id"), None) :: Nil,
+                UnresolvedRelation(TableIdentifier("t0", Some("default")), None))),
+            Project(
+              UnresolvedAlias(UnresolvedAttribute("t0.id"), None) :: Nil,
+              UnresolvedRelation(TableIdentifier("t0", Some("default")), None))),
+          Project(
+            UnresolvedAlias(UnresolvedAttribute("t0.id"), None) :: Nil,
+            UnresolvedRelation(TableIdentifier("t0", Some("default")), None)))))
+
+    comparePlans(parsed2, expected2)
+  }
+
   test("subquery") {
     parser.parsePlan("select (select max(b) from s) ss from t")
     parser.parsePlan("select * from t where a = (select b from s)")