[SPARK-10437] [SQL] Support aggregation expressions in Order By

JIRA: https://issues.apache.org/jira/browse/SPARK-10437

If an expression in `SortOrder` is a resolved one, such as `count(1)`, the corresponding rule in `Analyzer` to make it work in order by will not be applied.

Author: Liang-Chi Hsieh <[email protected]>

Closes #8599 from viirya/orderby-agg.

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 {
@@ -598,9 +598,15 @@ class Analyzer(
               }
           }
 
-          Project(aggregate.output,
-            Sort(evaluatedOrderings, global,
-              aggregate.copy(aggregateExpressions = originalAggExprs ++ needsPushDown)))
+          // Since we don't rely on sort.resolved as the stop condition for this rule,
+          // we need to check this and prevent applying this rule multiple times
+          if (sortOrder == evaluatedOrderings) {
+            sort
+          } else {
+            Project(aggregate.output,
+              Sort(evaluatedOrderings, global,
+                aggregate.copy(aggregateExpressions = originalAggExprs ++ needsPushDown)))
+          }
         } catch {
           // Attempting to resolve in the aggregate can result in ambiguity.  When this happens,
           // just return the original plan.

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

@@ -1562,6 +1562,26 @@ 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)
+
+    checkAnswer(
+      sql(
+        """
+            |SELECT count(*)
+            |FROM orderByData
+            |GROUP BY a
+            |ORDER BY count(*)
+          """.stripMargin),
+      Row(2) :: Row(2) :: Row(2) :: Row(2) :: Nil)
+
+    checkAnswer(
+      sql(
+        """
+            |SELECT a
+            |FROM orderByData
+            |GROUP BY a
+            |ORDER BY a, count(*), sum(b)
+          """.stripMargin),
+      Row("1") :: Row("2") :: Row("3") :: Row("4") :: Nil)
   }
 
   test("SPARK-7952: fix the equality check between boolean and numeric types") {