MDEV-10120: Wrong result of UNION .. ORDER BY GROUP_CONCAT()

Reject queries that have aggregate functions with UNION as these
are not allowed by standard.

mysql-test/r/parser.result

@@ -943,11 +943,9 @@ ERROR 42000: You have an error in your SQL syntax; check the manual that corresp
 CREATE TABLE t1 (a INT);
 INSERT INTO t1 VALUES (10),(20),(30);
 SELECT 1 AS a UNION SELECT a FROM t1 GROUP BY a ORDER BY GROUP_CONCAT(a);
-a
-1
+ERROR HY000: Expression #1 of ORDER BY contains aggregate function and applies to a UNION
 SELECT 1 AS a UNION SELECT a FROM t1 GROUP BY a ORDER BY GROUP_CONCAT(a ORDER BY a);
-a
-1
+ERROR HY000: Expression #1 of ORDER BY contains aggregate function and applies to a UNION
 DROP TABLE t1;
 # UNION with a parenthesed term
 CREATE TABLE t1 (a INT);
@@ -1010,14 +1008,11 @@ DROP TABLE t1;
 CREATE TABLE t1 (a INT);
 INSERT INTO t1 VALUES (10),(20),(30);
 SELECT 1 AS a UNION SELECT a FROM t1 GROUP BY a WITH ROLLUP ORDER BY GROUP_CONCAT(a);
-a
-1
+ERROR HY000: Expression #1 of ORDER BY contains aggregate function and applies to a UNION
 SELECT 1 AS a UNION SELECT a FROM t1 GROUP BY a WITH ROLLUP ORDER BY GROUP_CONCAT(a ORDER BY a);
-a
-1
+ERROR HY000: Expression #1 of ORDER BY contains aggregate function and applies to a UNION
 SELECT 1 AS a UNION SELECT a FROM t1 GROUP BY a WITH ROLLUP ORDER BY GROUP_CONCAT(a ORDER BY a) LIMIT 1;
-a
-1
+ERROR HY000: Expression #1 of ORDER BY contains aggregate function and applies to a UNION
 DROP TABLE t1;
 # Derived table with ROLLUP
 CREATE TABLE t1 (a INT);

mysql-test/r/union.result

@@ -1757,8 +1757,7 @@ union
 select 4
 order by max(42) + max(1) + max(1) + max(1) + max(1) + max(1)
 ;
-foo
-1
+ERROR HY000: Expression #1 of ORDER BY contains aggregate function and applies to a UNION
 prepare stmt1 from 'select 1 as foo
 union
 select 2
@@ -1768,12 +1767,7 @@ union
 select 4
 order by max(42) + max(1) + max(1) + max(1) + max(1) + max(1)
 ';
-execute stmt1;
-foo
-1
-execute stmt1;
-foo
-1
+ERROR HY000: Expression #1 of ORDER BY contains aggregate function and applies to a UNION
 select 1 as foo
 union
 select 2
@@ -1783,8 +1777,7 @@ union
 (select 4)
 order by max(42) + max(1) + max(1) + max(1) + max(1) + max(1)
 ;
-foo
-1
+ERROR HY000: Expression #1 of ORDER BY contains aggregate function and applies to a UNION
 prepare stmt1 from 'select 1 as foo
 union
 select 2
@@ -1794,13 +1787,7 @@ union
 (select 4)
 order by max(42) + max(1) + max(1) + max(1) + max(1) + max(1)
 ';
-execute stmt1;
-foo
-1
-execute stmt1;
-foo
-1
-deallocate prepare stmt1;
+ERROR HY000: Expression #1 of ORDER BY contains aggregate function and applies to a UNION
 End of 5.1 tests
 #
 # mdev-5091: Asseirtion failure for UNION with ORDER BY 
@@ -2299,3 +2286,11 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
 Warnings:
 Note	1003	select 1 AS `1`,2 AS `2` union all select 1 AS `i`,count(0) AS `COUNT(*)` from `test`.`t2` where 1 group by 1 having 0
 DROP TABLE t1,t2;
+#
+# MDEV-10120: Wrong result of UNION .. ORDER BY GROUP_CONCAT()
+#
+CREATE TABLE t1 (a INT);
+INSERT t1 VALUES (1),(2),(3);
+(SELECT 1 AS a) UNION (SELECT a FROM t1 GROUP BY a) ORDER BY GROUP_CONCAT(a);
+ERROR HY000: Expression #1 of ORDER BY contains aggregate function and applies to a UNION
+DROP TABLE t1;

mysql-test/t/parser.test

@@ -1090,7 +1090,9 @@ CREATE TABLE t1 AS SELECT 1 LIMIT 1 UNION SELECT 2;
 --echo # For now, we're testing the parser.
 CREATE TABLE t1 (a INT);
 INSERT INTO t1 VALUES (10),(20),(30);
+--error ER_AGGREGATE_ORDER_FOR_UNION
 SELECT 1 AS a UNION SELECT a FROM t1 GROUP BY a ORDER BY GROUP_CONCAT(a);
+--error ER_AGGREGATE_ORDER_FOR_UNION
 SELECT 1 AS a UNION SELECT a FROM t1 GROUP BY a ORDER BY GROUP_CONCAT(a ORDER BY a);
 DROP TABLE t1;
 
@@ -1131,8 +1133,11 @@ DROP TABLE t1;
 
 CREATE TABLE t1 (a INT);
 INSERT INTO t1 VALUES (10),(20),(30);
+--error ER_AGGREGATE_ORDER_FOR_UNION
 SELECT 1 AS a UNION SELECT a FROM t1 GROUP BY a WITH ROLLUP ORDER BY GROUP_CONCAT(a);
+--error ER_AGGREGATE_ORDER_FOR_UNION
 SELECT 1 AS a UNION SELECT a FROM t1 GROUP BY a WITH ROLLUP ORDER BY GROUP_CONCAT(a ORDER BY a);
+--error ER_AGGREGATE_ORDER_FOR_UNION
 SELECT 1 AS a UNION SELECT a FROM t1 GROUP BY a WITH ROLLUP ORDER BY GROUP_CONCAT(a ORDER BY a) LIMIT 1;
 DROP TABLE t1;
 

mysql-test/t/union.test

@@ -1184,11 +1184,11 @@ select 4
 order by max(42) + max(1) + max(1) + max(1) + max(1) + max(1)
 ;
 
+--error ER_AGGREGATE_ORDER_FOR_UNION
 eval $my_stmt;
 
+--error ER_AGGREGATE_ORDER_FOR_UNION
 eval prepare stmt1 from '$my_stmt';
-execute stmt1;
-execute stmt1;
 
 let $my_stmt=
 select 1 as foo
@@ -1201,13 +1201,11 @@ union
 order by max(42) + max(1) + max(1) + max(1) + max(1) + max(1)
 ;
 
+--error ER_AGGREGATE_ORDER_FOR_UNION
 eval $my_stmt;
 
+--error ER_AGGREGATE_ORDER_FOR_UNION
 eval prepare stmt1 from '$my_stmt';
-execute stmt1;
-execute stmt1;
-
-deallocate prepare stmt1;
 
 --echo End of 5.1 tests
 
@@ -1637,3 +1635,14 @@ eval $q;
 eval EXPLAIN EXTENDED $q;
 
 DROP TABLE t1,t2;
+
+--echo #
+--echo # MDEV-10120: Wrong result of UNION .. ORDER BY GROUP_CONCAT()
+--echo #
+
+CREATE TABLE t1 (a INT);
+INSERT t1 VALUES (1),(2),(3);
+
+--error ER_AGGREGATE_ORDER_FOR_UNION
+(SELECT 1 AS a) UNION (SELECT a FROM t1 GROUP BY a) ORDER BY GROUP_CONCAT(a);
+DROP TABLE t1;

sql/sql_select.cc

@@ -22709,10 +22709,13 @@ int setup_order(THD *thd, Ref_ptr_array ref_pointer_array, TABLE_LIST *tables,
                 List<Item> &fields, List<Item> &all_fields, ORDER *order,
                 bool from_window_spec)
 { 
+  SELECT_LEX *select = thd->lex->current_select;
   enum_parsing_place context_analysis_place=
                      thd->lex->current_select->context_analysis_place;
   thd->where="order clause";
-  for (; order; order=order->next)
+  const bool for_union = select->master_unit()->is_union() &&
+                         select == select->master_unit()->fake_select_lex;
+  for (uint number = 1; order; order=order->next, number++)
   {
     if (find_order_in_list(thd, ref_pointer_array, tables, order, fields,
                            all_fields, false, true, from_window_spec))
@@ -22723,6 +22726,18 @@ int setup_order(THD *thd, Ref_ptr_array ref_pointer_array, TABLE_LIST *tables,
       my_error(ER_WINDOW_FUNCTION_IN_WINDOW_SPEC, MYF(0));
       return 1;
     }
+
+    /*
+      UNION queries cannot be used with an aggregate function in
+      an ORDER BY clause
+    */
+
+    if (for_union && (*order->item)->with_sum_func)
+    {
+      my_error(ER_AGGREGATE_ORDER_FOR_UNION, MYF(0), number);
+      return 1;
+    }
+
     if (from_window_spec && (*order->item)->with_sum_func &&
         (*order->item)->type() != Item::SUM_FUNC_ITEM)
       (*order->item)->split_sum_func(thd, ref_pointer_array,