Add more unit test and comments

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/Analyzer.scala

@@ -193,28 +193,34 @@ class Analyzer(
     }
 
     def apply(plan: LogicalPlan): LogicalPlan = plan transform {
+      case a if !a.childrenResolved => a // be sure all of the children are resolved.
       case a: Cube =>
         GroupingSets(bitmasks(a), a.groupByExprs, a.child, a.aggregations)
       case a: Rollup =>
         GroupingSets(bitmasks(a), a.groupByExprs, a.child, a.aggregations)
       case x: GroupingSets =>
         val gid = AttributeReference(VirtualColumn.groupingIdName, IntegerType, false)()
 
+        // the complex expression (non-attribute expressions) in the GROUP BY keys
         val nonAttributeGroupByExpression = new ArrayBuffer[Alias]()
         val groupByExprPairs = x.groupByExprs.map(_ match {
           case e: NamedExpression => (e, e)
           case other => {
             val alias = Alias(other, other.toString)()
             nonAttributeGroupByExpression += alias
-            (other, alias.toAttribute)
+            (other, alias.toAttribute) // (Aliased complex expression, the associated attribute)
           }
         })
 
+        // substitute the complex expression for aggregations.
         val aggregation = x.aggregations.map(expr => expr.transformDown {
           case e => groupByExprPairs.find(_._1.semanticEquals(e)).map(_._2).getOrElse(e)
         }.asInstanceOf[NamedExpression])
 
+        // substitute the group by expressions.
         val newGroupByExprs = groupByExprPairs.map(_._2)
+
+        // add an additional projection if contains the complex expression in the GROUP BY keys
         val child = if (nonAttributeGroupByExpression.length > 0) {
           Project(x.child.output ++ nonAttributeGroupByExpression, x.child)
         } else {

sql/hive/src/test/resources/golden/SPARK-8976 Wrong Result for CUBE #2-0-7a511f02a16f0af4f810b1666cfcd896

@@ -0,0 +1,10 @@
+1	NULL	-3	2
+1	NULL	-1	2
+1	NULL	3	2
+1	NULL	4	2
+1	NULL	5	2
+1	NULL	6	2
+1	NULL	12	2
+1	NULL	14	2
+1	NULL	15	2
+1	NULL	22	2

sql/hive/src/test/resources/golden/SPARK-8976 Wrong Result for GroupingSet-0-8c14c24670a4b06c440346277ce9cf1c

@@ -0,0 +1,10 @@
+1	NULL	-3	2
+1	NULL	-1	2
+1	NULL	3	2
+1	NULL	4	2
+1	NULL	5	2
+1	NULL	6	2
+1	NULL	12	2
+1	NULL	14	2
+1	NULL	15	2
+1	NULL	22	2

sql/hive/src/test/resources/golden/SPARK-8976 Wrong Result for Rollup #1-0-a78e3dbf242f240249e36b3d3fd0926a

@@ -0,0 +1,6 @@
+500	NULL	0
+91	0	1
+84	1	1
+105	2	1
+113	3	1
+107	4	1

sql/hive/src/test/resources/golden/SPARK-8976 Wrong Result for Rollup #2-0-bf180c9d1a18f61b9d9f31bb0115cf89

@@ -0,0 +1,10 @@
+1	0	5	3
+1	0	15	3
+1	0	25	3
+1	0	60	3
+1	0	75	3
+1	0	80	3
+1	0	100	3
+1	0	140	3
+1	0	145	3
+1	0	150	3

sql/hive/src/test/resources/golden/SPARK-8976 Wrong Result for Rollup #3-0-9257085d123728730be96b6d9fbb84ce

@@ -0,0 +1,10 @@
+1	0	5	3
+1	0	15	3
+1	0	25	3
+1	0	60	3
+1	0	75	3
+1	0	80	3
+1	0	100	3
+1	0	140	3
+1	0	145	3
+1	0	150	3

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

@@ -85,11 +85,60 @@ class HiveQuerySuite extends HiveComparisonTest with BeforeAndAfter {
     }
   }
 
-  createQueryTest("SPARK-8976 Wrong Result for Rollup",
+  createQueryTest("SPARK-8976 Wrong Result for Rollup #1",
     """
       SELECT count(*) AS cnt, key % 5,GROUPING__ID FROM src group by key%5 WITH ROLLUP
     """.stripMargin)
 
+  createQueryTest("SPARK-8976 Wrong Result for Rollup #2",
+    """
+      SELECT
+        count(*) AS cnt,
+        key % 5 as k1,
+        key-5 as k2,
+        GROUPING__ID as k3
+      FROM src group by key%5, key-5
+      WITH ROLLUP ORDER BY cnt, k1, k2, k3 LIMIT 10
+    """.stripMargin)
+
+  createQueryTest("SPARK-8976 Wrong Result for Rollup #3",
+    """
+      SELECT
+        count(*) AS cnt,
+        key % 5 as k1,
+        key-5 as k2,
+        GROUPING__ID as k3
+      FROM (SELECT key, key%2, key - 5 FROM src) t group by key%5, key-5
+      WITH ROLLUP ORDER BY cnt, k1, k2, k3 LIMIT 10
+    """.stripMargin)
+
+  createQueryTest("SPARK-8976 Wrong Result for CUBE #1",
+    """
+      SELECT count(*) AS cnt, key % 5,GROUPING__ID FROM src group by key%5 WITH CUBE
+    """.stripMargin)
+
+  createQueryTest("SPARK-8976 Wrong Result for CUBE #2",
+    """
+      SELECT
+        count(*) AS cnt,
+        key % 5 as k1,
+        key-5 as k2,
+        GROUPING__ID as k3
+      FROM (SELECT key, key%2, key - 5 FROM src) t group by key%5, key-5
+      WITH CUBE ORDER BY cnt, k1, k2, k3 LIMIT 10
+    """.stripMargin)
+
+  createQueryTest("SPARK-8976 Wrong Result for GroupingSet",
+    """
+      SELECT
+        count(*) AS cnt,
+        key % 5 as k1,
+        key-5 as k2,
+        GROUPING__ID as k3
+      FROM (SELECT key, key%2, key - 5 FROM src) t group by key%5, key-5
+      GROUPING SETS (key%5, key-5) ORDER BY cnt, k1, k2, k3 LIMIT 10
+    """.stripMargin)
+
   createQueryTest("insert table with generator with column name",
     """
       |  CREATE TABLE gen_tmp (key Int);