Fixed bug #24653.

The bug report has demonstrated the following two problems.
1. If an ORDER/GROUP BY list includes a constant expression being 
optimized away and, at the same time, containing single-row
subselects that return more that one row, no error is reported.
Strictly speaking the standard allows to ignore error in this case.
Yet, now a corresponding fatal error is reported in this case.
2. If a query requires sorting by expressions containing single-row
subselects that, however, return more than one row, then the execution
of the query may cause a server crash. 
To fix this some code has been added that blocks execution of a subselect
item in case of a fatal error in the method Item_subselect::exec.

mysql-test/r/subselect.result

@@ -3026,3 +3026,77 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	2	
 2	SUBQUERY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE
 DROP TABLE t1;
+CREATE TABLE t1 (a int);
+INSERT INTO t1 VALUES (2), (4), (1), (3);
+CREATE TABLE t2 (b int, c int);
+INSERT INTO t2 VALUES
+(2,1), (1,3), (2,1), (4,4), (2,2), (1,4);
+SELECT a FROM t1 ORDER BY (SELECT c FROM t2 WHERE b > 2 );
+a
+2
+4
+1
+3
+SELECT a FROM t1 ORDER BY (SELECT c FROM t2 WHERE b > 1);
+ERROR 21000: Subquery returns more than 1 row
+SELECT a FROM t1 ORDER BY (SELECT c FROM t2 WHERE b > 2), a;
+a
+1
+2
+3
+4
+SELECT a FROM t1 ORDER BY (SELECT c FROM t2 WHERE b > 1), a;
+ERROR 21000: Subquery returns more than 1 row
+SELECT b, MAX(c) FROM t2 GROUP BY b, (SELECT c FROM t2 WHERE b > 2);
+b	MAX(c)
+1	4
+2	2
+4	4
+SELECT b, MAX(c) FROM t2 GROUP BY b, (SELECT c FROM t2 WHERE b > 1);
+ERROR 21000: Subquery returns more than 1 row
+SELECT a FROM t1 GROUP BY a
+HAVING IFNULL((SELECT b FROM t2 WHERE b > 2),
+(SELECT c FROM t2 WHERE c=a AND b > 2 ORDER BY b)) > 3;
+a
+1
+2
+3
+4
+SELECT a FROM t1 GROUP BY a
+HAVING IFNULL((SELECT b FROM t2 WHERE b > 1),
+(SELECT c FROM t2 WHERE c=a AND b > 2 ORDER BY b)) > 3;
+ERROR 21000: Subquery returns more than 1 row
+SELECT a FROM t1 GROUP BY a
+HAVING IFNULL((SELECT b FROM t2 WHERE b > 4),
+(SELECT c FROM t2 WHERE c=a AND b > 2 ORDER BY b)) > 3;
+a
+4
+SELECT a FROM t1 GROUP BY a
+HAVING IFNULL((SELECT b FROM t2 WHERE b > 4),
+(SELECT c FROM t2 WHERE c=a AND b > 1 ORDER BY b)) > 3;
+ERROR 21000: Subquery returns more than 1 row
+SELECT a FROM t1 
+ORDER BY IFNULL((SELECT b FROM t2 WHERE b > 2),
+(SELECT c FROM t2 WHERE c=a AND b > 2 ORDER BY b));
+a
+2
+4
+1
+3
+SELECT a FROM t1 
+ORDER BY IFNULL((SELECT b FROM t2 WHERE b > 1),
+(SELECT c FROM t2 WHERE c=a AND b > 1 ORDER BY b));
+ERROR 21000: Subquery returns more than 1 row
+SELECT a FROM t1 
+ORDER BY IFNULL((SELECT b FROM t2 WHERE b > 4),
+(SELECT c FROM t2 WHERE c=a AND b > 2 ORDER BY b));
+a
+2
+1
+3
+4
+SELECT a FROM t1 
+ORDER BY IFNULL((SELECT b FROM t2 WHERE b > 4),
+(SELECT c FROM t2 WHERE c=a AND b > 1 ORDER BY b));
+ERROR 21000: Subquery returns more than 1 row
+DROP TABLE t1,t2;

mysql-test/t/subselect.test

@@ -1993,4 +1993,63 @@ SELECT a FROM t1 WHERE (SELECT 1 FROM DUAL WHERE 1=0) IS NULL;
 EXPLAIN SELECT a FROM t1 WHERE (SELECT 1 FROM DUAL WHERE 1=0) IS NULL;
 
 DROP TABLE t1;
+
+#
+# Bug 24653: sorting by expressions containing subselects 
+#            that return more than one row
+#
+
+CREATE TABLE t1 (a int);
+INSERT INTO t1 VALUES (2), (4), (1), (3);
+
+CREATE TABLE t2 (b int, c int);
+INSERT INTO t2 VALUES
+  (2,1), (1,3), (2,1), (4,4), (2,2), (1,4);
+
+SELECT a FROM t1 ORDER BY (SELECT c FROM t2 WHERE b > 2 );
+--error 1242   
+SELECT a FROM t1 ORDER BY (SELECT c FROM t2 WHERE b > 1);  
+SELECT a FROM t1 ORDER BY (SELECT c FROM t2 WHERE b > 2), a;  
+--error 1242   
+SELECT a FROM t1 ORDER BY (SELECT c FROM t2 WHERE b > 1), a;
+ 
+SELECT b, MAX(c) FROM t2 GROUP BY b, (SELECT c FROM t2 WHERE b > 2);
+--error 1242
+SELECT b, MAX(c) FROM t2 GROUP BY b, (SELECT c FROM t2 WHERE b > 1);
+
+
+SELECT a FROM t1 GROUP BY a
+  HAVING IFNULL((SELECT b FROM t2 WHERE b > 2),
+                (SELECT c FROM t2 WHERE c=a AND b > 2 ORDER BY b)) > 3;
+--error 1242
+SELECT a FROM t1 GROUP BY a
+  HAVING IFNULL((SELECT b FROM t2 WHERE b > 1),
+                (SELECT c FROM t2 WHERE c=a AND b > 2 ORDER BY b)) > 3;
+
+SELECT a FROM t1 GROUP BY a
+  HAVING IFNULL((SELECT b FROM t2 WHERE b > 4),
+                (SELECT c FROM t2 WHERE c=a AND b > 2 ORDER BY b)) > 3;
+--error 1242 
+SELECT a FROM t1 GROUP BY a
+  HAVING IFNULL((SELECT b FROM t2 WHERE b > 4),
+                (SELECT c FROM t2 WHERE c=a AND b > 1 ORDER BY b)) > 3;
+
+SELECT a FROM t1 
+  ORDER BY IFNULL((SELECT b FROM t2 WHERE b > 2),
+                  (SELECT c FROM t2 WHERE c=a AND b > 2 ORDER BY b));
+--error 1242
+SELECT a FROM t1 
+  ORDER BY IFNULL((SELECT b FROM t2 WHERE b > 1),
+                  (SELECT c FROM t2 WHERE c=a AND b > 1 ORDER BY b));
+
+SELECT a FROM t1 
+  ORDER BY IFNULL((SELECT b FROM t2 WHERE b > 4),
+                  (SELECT c FROM t2 WHERE c=a AND b > 2 ORDER BY b));
+--error 1242
+SELECT a FROM t1 
+  ORDER BY IFNULL((SELECT b FROM t2 WHERE b > 4),
+                  (SELECT c FROM t2 WHERE c=a AND b > 1 ORDER BY b));
+
+DROP TABLE t1,t2; 
+
 # End of 4.1 tests

sql/filesort.cc

@@ -387,7 +387,8 @@ static ha_rows find_all_keys(SORTPARAM *param, SQL_SELECT *select,
   byte *ref_pos,*next_pos,ref_buff[MAX_REFLENGTH];
   my_off_t record;
   TABLE *sort_form;
-  volatile my_bool *killed= &current_thd->killed;
+  THD *thd= current_thd;
+  volatile my_bool *killed= &thd->killed;
   handler *file;
   DBUG_ENTER("find_all_keys");
   DBUG_PRINT("info",("using: %s",(select?select->quick?"ranges":"where":"every row")));
@@ -474,6 +475,9 @@ static ha_rows find_all_keys(SORTPARAM *param, SQL_SELECT *select,
     }
     else
       file->unlock_row();
+    /* It does not make sense to read more keys in case of a fatal error */
+    if (thd->net.report_error)
+      DBUG_RETURN(HA_POS_ERROR);
   }
   (void) file->extra(HA_EXTRA_NO_CACHE);	/* End cacheing of records */
   if (!next_pos)

sql/item.cc

@@ -47,6 +47,7 @@ Item::Item():
   collation.set(&my_charset_bin, DERIVATION_COERCIBLE);
   name= 0;
   decimals= 0; max_length= 0;
+  with_subselect= 0;
 
   /* Put item in free list so that we can free all items at end */
   THD *thd= current_thd;

sql/item.h

@@ -142,6 +142,9 @@ public:
   my_bool with_sum_func;
   my_bool fixed;                        /* If item fixed with fix_fields */
   DTCollation collation;
+  my_bool with_subselect;               /* If this item is a subselect or some
+                                           of its arguments is or contains a
+                                           subselect */
 
   // alloc & destruct is done as start of select using sql_alloc
   Item();

sql/item_cmpfunc.cc

@@ -2139,6 +2139,7 @@ Item_cond::fix_fields(THD *thd, TABLE_LIST *tables, Item **ref)
     and_tables_cache&=      tmp_table_map;
     const_item_cache&=	    item->const_item();
     with_sum_func=	    with_sum_func || item->with_sum_func;
+    with_subselect|=        item->with_subselect;
     if (item->maybe_null)
       maybe_null=1;
   }
@@ -2351,7 +2352,7 @@ longlong Item_func_isnull::val_int()
     Handle optimization if the argument can't be null
     This has to be here because of the test in update_used_tables().
   */
-  if (!used_tables_cache)
+  if (!used_tables_cache && !with_subselect)
     return cached_value;
   return args[0]->is_null() ? 1: 0;
 }
@@ -2360,7 +2361,7 @@ longlong Item_is_not_null_test::val_int()
 {
   DBUG_ASSERT(fixed == 1);
   DBUG_ENTER("Item_is_not_null_test::val_int");
-  if (!used_tables_cache)
+  if (!used_tables_cache && !with_subselect)
   {
     owner->was_null|= (!cached_value);
     DBUG_PRINT("info", ("cached :%d", cached_value));
@@ -2387,7 +2388,7 @@ void Item_is_not_null_test::update_used_tables()
   else
   {
     args[0]->update_used_tables();
-    if (!(used_tables_cache=args[0]->used_tables()))
+    if (!(used_tables_cache=args[0]->used_tables()) && !with_subselect)
     {
       /* Remember if the value is always NULL or never NULL */
       cached_value= (longlong) !args[0]->is_null();

sql/item_cmpfunc.h

@@ -843,7 +843,8 @@ public:
     else
     {
       args[0]->update_used_tables();
-      if ((const_item_cache= !(used_tables_cache= args[0]->used_tables())))
+      if ((const_item_cache= !(used_tables_cache= args[0]->used_tables())) &&
+           !with_subselect)
       {
 	/* Remember if the value is always NULL or never NULL */
 	cached_value= (longlong) args[0]->is_null();

sql/item_func.cc

@@ -177,6 +177,7 @@ Item_func::fix_fields(THD *thd, TABLE_LIST *tables, Item **ref)
       used_tables_cache|=     item->used_tables();
       not_null_tables_cache|= item->not_null_tables();
       const_item_cache&=      item->const_item();
+      with_subselect|=        item->with_subselect;
     }
   }
   fix_length_and_dec();

sql/item_subselect.cc

@@ -39,6 +39,7 @@ Item_subselect::Item_subselect():
   engine(0), old_engine(0), used_tables_cache(0), have_to_be_excluded(0),
   const_item_cache(1), engine_changed(0), changed(0)
 {
+  with_subselect= 1;
   reset();
   /*
     item value is NULL if select_subselect not changed this value
@@ -201,6 +202,9 @@ bool Item_subselect::exec()
     mem root
   */
   thd->mem_root= &thd->main_mem_root;
+  if (thd->net.report_error)
+  /* Do not execute subselect in case of a fatal error */
+    return 1;
   res= engine->exec();
   thd->mem_root= old_root;
 

sql/sql_select.cc

@@ -644,6 +644,13 @@ JOIN::optimize()
   {
     ORDER *org_order= order;
     order=remove_const(this, order,conds,1, &simple_order);
+    if (thd->net.report_error)
+    {
+      error= 1;
+      DBUG_PRINT("error",("Error from remove_const"));
+      DBUG_RETURN(1);
+    }
+
     /*
       If we are using ORDER BY NULL or ORDER BY const_expression,
       return result in any order (even if we are using a GROUP BY)
@@ -747,6 +754,12 @@ JOIN::optimize()
     group_list= remove_const(this, (old_group_list= group_list), conds,
                              rollup.state == ROLLUP::STATE_NONE,
 			     &simple_group);
+    if (thd->net.report_error)
+    {
+      error= 1;
+      DBUG_PRINT("error",("Error from remove_const"));
+      DBUG_RETURN(1);
+    }
     if (old_group_list && !group_list)
       select_distinct= 0;
   }
@@ -763,6 +776,12 @@ JOIN::optimize()
   {
     group_list= procedure->group= remove_const(this, procedure->group, conds,
 					       1, &simple_group);
+    if (thd->net.report_error)
+    {
+      error= 1;
+      DBUG_PRINT("error",("Error from remove_const"));
+      DBUG_RETURN(1);
+    }   
     calc_group_buffer(this, group_list);
   }
 
@@ -4428,6 +4447,8 @@ remove_const(JOIN *join,ORDER *first_order, COND *cond,
       *simple_order=0;				// Must do a temp table to sort
     else if (!(order_tables & not_const_tables))
     {
+      if (order->item[0]->with_subselect)
+        order->item[0]->val_str(&order->item[0]->str_value);
       DBUG_PRINT("info",("removing: %s", order->item[0]->full_name()));
       continue;					// skip const item
     }