Bug#11766675 - 59839: Aggregation followed by subquery yields wrong result

The loop that was looping over subqueries' references to outer field used a
local boolean variable to tell whether the field was grouped or not. But the
implementor failed to reset the variable after each iteration. Thus a field
that was not directly aggregated appeared to be.

Fixed by resetting the variable upon each new iteration.

mysql-test/r/group_by.result

@@ -1855,4 +1855,40 @@ ON 1 WHERE t2.f1 > 1 GROUP BY t2.f1;
 COUNT(*)
 2
 DROP TABLE t1;
+#
+# Bug#59839: Aggregation followed by subquery yields wrong result
+#
+CREATE TABLE t1 (
+a INT,
+b INT,
+c INT,
+KEY (a, b)
+);
+INSERT INTO t1 VALUES
+( 1, 1,  1 ),
+( 1, 2,  2 ),
+( 1, 3,  3 ),
+( 1, 4,  6 ),
+( 1, 5,  5 ),
+( 1, 9, 13 ),
+( 2, 1,  6 ),
+( 2, 2,  7 ),
+( 2, 3,  8 );
+EXPLAIN
+SELECT a, AVG(t1.b),
+(SELECT t11.c FROM t1 t11 WHERE t11.a = t1.a AND t11.b = AVG(t1.b)) AS t11c,
+(SELECT t12.c FROM t1 t12 WHERE t12.a = t1.a AND t12.b = AVG(t1.b)) AS t12c
+FROM t1 GROUP BY a;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	index	NULL	a	10	NULL	9	Using index
+3	DEPENDENT SUBQUERY	t12	ref	a	a	10	func,func	2	Using where
+2	DEPENDENT SUBQUERY	t11	ref	a	a	10	func,func	2	Using where
+SELECT a, AVG(t1.b),
+(SELECT t11.c FROM t1 t11 WHERE t11.a = t1.a AND t11.b = AVG(t1.b)) AS t11c,
+(SELECT t12.c FROM t1 t12 WHERE t12.a = t1.a AND t12.b = AVG(t1.b)) AS t12c
+FROM t1 GROUP BY a;
+a	AVG(t1.b)	t11c	t12c
+1	4.0000	6	6
+2	2.0000	7	7
+DROP TABLE t1;
 # End of 5.1 tests

mysql-test/t/group_by.test

@@ -1247,4 +1247,41 @@ ON 1 WHERE t2.f1 > 1 GROUP BY t2.f1;
 
 DROP TABLE t1;
 
+--echo #
+--echo # Bug#59839: Aggregation followed by subquery yields wrong result
+--echo #
+
+CREATE TABLE t1 (
+  a INT,
+  b INT,
+  c INT,
+  KEY (a, b)
+);
+
+INSERT INTO t1 VALUES
+  ( 1, 1,  1 ),
+  ( 1, 2,  2 ),
+  ( 1, 3,  3 ),
+  ( 1, 4,  6 ),
+  ( 1, 5,  5 ),
+  ( 1, 9, 13 ),
+
+  ( 2, 1,  6 ),
+  ( 2, 2,  7 ),
+  ( 2, 3,  8 );
+
+EXPLAIN
+SELECT a, AVG(t1.b),
+(SELECT t11.c FROM t1 t11 WHERE t11.a = t1.a AND t11.b = AVG(t1.b)) AS t11c,
+(SELECT t12.c FROM t1 t12 WHERE t12.a = t1.a AND t12.b = AVG(t1.b)) AS t12c
+FROM t1 GROUP BY a;
+
+SELECT a, AVG(t1.b),
+(SELECT t11.c FROM t1 t11 WHERE t11.a = t1.a AND t11.b = AVG(t1.b)) AS t11c,
+(SELECT t12.c FROM t1 t12 WHERE t12.a = t1.a AND t12.b = AVG(t1.b)) AS t12c
+FROM t1 GROUP BY a;
+
+DROP TABLE t1;
+
+
 --echo # End of 5.1 tests

sql/sql_select.cc

@@ -278,61 +278,65 @@ bool handle_select(THD *thd, LEX *lex, select_result *result,
 }
 
 
-/*
+/**
   Fix fields referenced from inner selects.
 
-  SYNOPSIS
-    fix_inner_refs()
-    thd               Thread handle
-    all_fields        List of all fields used in select
-    select            Current select
-    ref_pointer_array Array of references to Items used in current select
-    group_list        GROUP BY list (is NULL by default)
+  @param thd               Thread handle
+  @param all_fields        List of all fields used in select
+  @param select            Current select
+  @param ref_pointer_array Array of references to Items used in current select
+  @param group_list        GROUP BY list (is NULL by default)
 
-  DESCRIPTION
-    The function serves 3 purposes - adds fields referenced from inner
-    selects to the current select list, resolves which class to use
-    to access referenced item (Item_ref of Item_direct_ref) and fixes
-    references (Item_ref objects) to these fields.
+  @details
+    The function serves 3 purposes
+
+    - adds fields referenced from inner query blocks to the current select list
+
+    - Decides which class to use to reference the items (Item_ref or
+      Item_direct_ref)
 
-    If a field isn't already in the select list and the ref_pointer_array
+    - fixes references (Item_ref objects) to these fields.
+
+    If a field isn't already on the select list and the ref_pointer_array
     is provided then it is added to the all_fields list and the pointer to
     it is saved in the ref_pointer_array.
 
     The class to access the outer field is determined by the following rules:
-    1. If the outer field isn't used under an aggregate function
-      then the Item_ref class should be used.
-    2. If the outer field is used under an aggregate function and this
-      function is aggregated in the select where the outer field was
-      resolved or in some more inner select then the Item_direct_ref
-      class should be used.
-      Also it should be used if we are grouping by a subquery containing
-      the outer field.
+
+    -#. If the outer field isn't used under an aggregate function then the
+        Item_ref class should be used.
+
+    -#. If the outer field is used under an aggregate function and this
+        function is, in turn, aggregated in the query block where the outer
+        field was resolved or some query nested therein, then the
+        Item_direct_ref class should be used. Also it should be used if we are
+        grouping by a subquery containing the outer field.
+
     The resolution is done here and not at the fix_fields() stage as
-    it can be done only after sum functions are fixed and pulled up to
-    selects where they are have to be aggregated.
+    it can be done only after aggregate functions are fixed and pulled up to
+    selects where they are to be aggregated.
+
     When the class is chosen it substitutes the original field in the
     Item_outer_ref object.
 
     After this we proceed with fixing references (Item_outer_ref objects) to
     this field from inner subqueries.
 
-  RETURN
-    TRUE  an error occured
-    FALSE ok
-*/
+  @return Status
+  @retval true An error occured.
+  @retval false OK.
+ */
 
 bool
 fix_inner_refs(THD *thd, List<Item> &all_fields, SELECT_LEX *select,
                  Item **ref_pointer_array, ORDER *group_list)
 {
   Item_outer_ref *ref;
-  bool res= FALSE;
-  bool direct_ref= FALSE;
 
   List_iterator<Item_outer_ref> ref_it(select->inner_refs_list);
   while ((ref= ref_it++))
   {
+    bool direct_ref= false;
     Item *item= ref->outer_ref;
     Item **item_ref= ref->ref;
     Item_ref *new_ref;
@@ -404,7 +408,7 @@ fix_inner_refs(THD *thd, List<Item> &all_fields, SELECT_LEX *select,
       return TRUE;
     thd->used_tables|= item->used_tables();
   }
-  return res;
+  return false;
 }
 
 /**