Bug #21540: Subqueries with no from and aggregate functions return

            wrong results
 Mark the containing Item(s) (Item_subselect descendant usually) of 
 a subselect as containing aggregate functions if it has references
 to aggregates functions that are calculated outside its context.
 This tels end_send_group() not to make an Item_subselect descendant in
 select list a copy and causes the correct value being returned.

mysql-test/r/func_group.result

@@ -997,7 +997,7 @@ SELECT SQL_NO_CACHE
 WHERE ttt.a = ccc.b AND ttt.a = t.a GROUP BY ttt.a) AS minid   
 FROM t1 t, t2 c WHERE t.a = c.b;
 minid
-NULL
+1
 DROP TABLE t1,t2;
 create table t1 select variance(0);
 show create table t1;

mysql-test/r/subselect.result

@@ -3368,3 +3368,64 @@ ORDER BY t1.t DESC LIMIT 1);
 i1	i2	t	i1	i2	t
 24	1	2005-05-27 12:40:30	24	1	2006-06-20 12:29:40
 DROP TABLE t1, t2;
+CREATE TABLE t1 (a INT, b INT);
+CREATE TABLE t2 (a INT);
+INSERT INTO t2 values (1);
+INSERT INTO t1 VALUES (1,1),(1,2),(2,3),(3,4);
+SELECT (SELECT COUNT(DISTINCT t1.b) from t2) FROM t1 GROUP BY t1.a;
+(SELECT COUNT(DISTINCT t1.b) from t2)
+2
+1
+1
+SELECT (SELECT COUNT(DISTINCT t1.b) from t2 union select 1 from t2 where 12 < 3)
+FROM t1 GROUP BY t1.a;
+(SELECT COUNT(DISTINCT t1.b) from t2 union select 1 from t2 where 12 < 3)
+2
+1
+1
+SELECT COUNT(DISTINCT t1.b), (SELECT COUNT(DISTINCT t1.b)) FROM t1 GROUP BY t1.a;
+COUNT(DISTINCT t1.b)	(SELECT COUNT(DISTINCT t1.b))
+2	2
+1	1
+1	1
+SELECT COUNT(DISTINCT t1.b), 
+(SELECT COUNT(DISTINCT t1.b) union select 1 from DUAL where 12 < 3)
+FROM t1 GROUP BY t1.a;
+COUNT(DISTINCT t1.b)	(SELECT COUNT(DISTINCT t1.b) union select 1 from DUAL where 12 < 3)
+2	2
+1	1
+1	1
+SELECT (
+SELECT (
+SELECT COUNT(DISTINCT t1.b)
+)
+) 
+FROM t1 GROUP BY t1.a;
+(
+SELECT (
+SELECT COUNT(DISTINCT t1.b)
+)
+)
+2
+1
+1
+SELECT (
+SELECT (
+SELECT (
+SELECT COUNT(DISTINCT t1.b)
+)
+) 
+FROM t1 GROUP BY t1.a LIMIT 1) 
+FROM t1 t2
+GROUP BY t2.a;
+(
+SELECT (
+SELECT (
+SELECT COUNT(DISTINCT t1.b)
+)
+) 
+FROM t1 GROUP BY t1.a LIMIT 1)
+2
+2
+2
+DROP TABLE t1,t2;

mysql-test/t/subselect.test

@@ -2280,3 +2280,34 @@ SELECT * FROM t1,t2
                     ORDER BY t1.t DESC LIMIT 1);
 
 DROP TABLE t1, t2;
+
+#
+# Bug #21540: Subqueries with no from and aggregate functions return 
+#              wrong results
+CREATE TABLE t1 (a INT, b INT);
+CREATE TABLE t2 (a INT);
+INSERT INTO t2 values (1);
+INSERT INTO t1 VALUES (1,1),(1,2),(2,3),(3,4);
+SELECT (SELECT COUNT(DISTINCT t1.b) from t2) FROM t1 GROUP BY t1.a;
+SELECT (SELECT COUNT(DISTINCT t1.b) from t2 union select 1 from t2 where 12 < 3)
+  FROM t1 GROUP BY t1.a;
+SELECT COUNT(DISTINCT t1.b), (SELECT COUNT(DISTINCT t1.b)) FROM t1 GROUP BY t1.a;
+SELECT COUNT(DISTINCT t1.b), 
+       (SELECT COUNT(DISTINCT t1.b) union select 1 from DUAL where 12 < 3)
+  FROM t1 GROUP BY t1.a;
+SELECT (
+    SELECT (
+      SELECT COUNT(DISTINCT t1.b)
+    )
+) 
+FROM t1 GROUP BY t1.a;
+SELECT (
+  SELECT (
+      SELECT (
+        SELECT COUNT(DISTINCT t1.b)
+      )
+  ) 
+  FROM t1 GROUP BY t1.a LIMIT 1) 
+FROM t1 t2
+GROUP BY t2.a;
+DROP TABLE t1,t2;  

sql/item_sum.cc

@@ -246,7 +246,27 @@ bool Item_sum::register_sum_func(THD *thd, Item **ref)
       aggr_sl->inner_sum_func_list->next= this;
     }
     aggr_sl->inner_sum_func_list= this;
-      
+    aggr_sl->with_sum_func= 1;
+
+    /* 
+      Mark Item_subselect(s) as containing aggregate function all the way up
+      to aggregate function's calculation context.
+      Note that we must not mark the Item of calculation context itself
+      because with_sum_func on the calculation context st_select_lex is
+      already set above.
+
+      with_sum_func being set for an Item means that this Item refers 
+      (somewhere in it, e.g. one of its arguments if it's a function) directly
+      or through intermediate items to an aggregate function that is calculated
+      in a context "outside" of the Item (e.g. in the current or outer select).
+
+      with_sum_func being set for an st_select_lex means that this st_select_lex
+      has aggregate functions directly referenced (i.e. not through a sub-select).
+    */
+    for (sl= thd->lex->current_select; 
+         sl && sl != aggr_sl && sl->master_unit()->item;
+         sl= sl->master_unit()->outer_select() )
+      sl->master_unit()->item->with_sum_func= 1;
   }
   return FALSE;
 }