Support aggregation expressions in Order By.

Author: viirya

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

@@ -561,7 +561,7 @@ class Analyzer(
         }
 
       case sort @ Sort(sortOrder, global, aggregate: Aggregate)
-        if aggregate.resolved && !sort.resolved =>
+        if aggregate.resolved =>
 
         // Try resolving the ordering as though it is in the aggregate clause.
         try {

sql/core/src/test/scala/org/apache/spark/sql/SQLQuerySuite.scala

@@ -1519,6 +1519,19 @@ class SQLQuerySuite extends QueryTest with SharedSQLContext {
             |ORDER BY sum(b) + 1
           """.stripMargin),
       Row("4", 3) :: Row("1", 7) :: Row("3", 11) :: Row("2", 15) :: Nil)
+
+    Seq("1" -> 3, "2" -> 7, "2" -> 8, "3" -> 5, "3" -> 6, "3" -> 2, "4" -> 1, "4" -> 2,
+      "4" -> 3, "4" -> 4).toDF("a", "b").registerTempTable("orderByData2")
+
+    checkAnswer(
+      sql(
+        """
+            |SELECT a, count(*)
+            |FROM orderByData2
+            |GROUP BY a
+            |ORDER BY count(*)
+          """.stripMargin),
+      Row("1", 1) :: Row("2", 2) :: Row("3", 3) :: Row("4", 4) :: Nil)
   }
 
   test("SPARK-7952: fix the equality check between boolean and numeric types") {