fixed cyclic reference bug

mysql-test/r/subselect.result:
  test of cyclic reference
mysql-test/t/subselect.test:
  test of cyclic reference
sql/share/czech/errmsg.txt:
  new error message
sql/share/danish/errmsg.txt:
  new error message
sql/share/dutch/errmsg.txt:
  new error message
sql/share/english/errmsg.txt:
  new error message
sql/share/estonian/errmsg.txt:
  new error message
sql/share/french/errmsg.txt:
  new error message
sql/share/german/errmsg.txt:
  new error message
sql/share/greek/errmsg.txt:
  new error message
sql/share/hungarian/errmsg.txt:
  new error message
sql/share/italian/errmsg.txt:
  new error message
sql/share/japanese/errmsg.txt:
  new error message
sql/share/korean/errmsg.txt:
  new error message
sql/share/norwegian-ny/errmsg.txt:
  new error message
sql/share/norwegian/errmsg.txt:
  new error message
sql/share/polish/errmsg.txt:
  new error message
sql/share/portuguese/errmsg.txt:
  new error message
sql/share/romanian/errmsg.txt:
  new error message
sql/share/russian/errmsg.txt:
  new error message
sql/share/serbian/errmsg.txt:
  new error message
sql/share/slovak/errmsg.txt:
  new error message
sql/share/spanish/errmsg.txt:
  new error message
sql/share/swedish/errmsg.txt:
  new error message
sql/share/ukrainian/errmsg.txt:
  new error message

include/mysqld_error.h

@@ -259,4 +259,5 @@
 #define ER_SUBSELECT_NO_1_ROW 1240
 #define ER_UNKNOWN_STMT_HANDLER 1241
 #define ER_CORRUPT_HELP_DB 1242
-#define ER_ERROR_MESSAGES 243
+#define ER_CYCLIC_REFERENCE 1243
+#define ER_ERROR_MESSAGES 244

mysql-test/r/subselect.result

@@ -8,6 +8,8 @@ SELECT (SELECT 1) UNION SELECT (SELECT 2);
 SELECT (SELECT (SELECT 0 UNION SELECT 0));
 (SELECT (SELECT 0 UNION SELECT 0))
 0
+SELECT (SELECT 1 FROM (SELECT 1) HAVING a=1) as a;
+Cyclic reference on subqueries
 drop table if exists t1,t2,t3,t4,t5,attend,clinic,inscrit;
 create table t1 (a int);
 create table t2 (a int, b int);
@@ -46,7 +48,7 @@ a	b
 1	7
 2	7
 3	8
-select * from t2 where t2.b=(select a from t3 order by 1 desc limit 1) 
+select * from t2 where t2.b=(select a from t3 order by 1 desc limit 1)
 union (select * from t4 where t4.b=(select max(t2.a)*4 from t2) order by a);
 a	b
 1	7

mysql-test/t/subselect.test

 select (select 2);
 SELECT (SELECT 1) UNION SELECT (SELECT 2);
 SELECT (SELECT (SELECT 0 UNION SELECT 0));
+-- error 1243
+SELECT (SELECT 1 FROM (SELECT 1) HAVING a=1) as a;
 drop table if exists t1,t2,t3,t4,t5,attend,clinic,inscrit;
 create table t1 (a int);
 create table t2 (a int, b int);
@@ -18,7 +20,7 @@ insert into t3 values (6),(7),(3);
 select * from t2 where t2.b=(select a from t3 order by 1 desc limit 1);
 select * from t2 where t2.b=(select a from t3 order by 1 desc limit 1) 
 union (select * from t4 order by a limit 2) limit 3;
-select * from t2 where t2.b=(select a from t3 order by 1 desc limit 1) 
+select * from t2 where t2.b=(select a from t3 order by 1 desc limit 1)
 union (select * from t4 where t4.b=(select max(t2.a)*4 from t2) order by a);
 explain select * from t2 where t2.b=(select a from t3 order by 1 desc limit 1) 
 union (select * from t4 where t4.b=(select max(t2.a)*4 from t2) order by a);

sql/item.cc

@@ -42,6 +42,20 @@ Item::Item()
   decimals=0; max_length=0;
   next=current_thd->free_list;			// Put in free list
   current_thd->free_list=this;
+  loop_id= 0;
+}
+
+bool Item::check_loop(uint id)
+{
+  DBUG_ENTER("Item::check_loop");
+  DBUG_PRINT("info", ("id %u, name %s", id, name));
+  if (loop_id == id)
+  {
+    DBUG_PRINT("info", ("id match"));
+    DBUG_RETURN(1);
+  }
+  loop_id= id;
+  DBUG_RETURN(0);
 }
 
 void Item::set_name(const char *str,uint length)
@@ -862,6 +876,11 @@ bool Item_ref::fix_fields(THD *thd,TABLE_LIST *tables, Item **reference)
       {
 	depended_from= last;
 	thd->lex.current_select->mark_as_dependent(last);
+	if (check_loop(thd->check_loops_counter++))
+	{
+	  my_message(ER_CYCLIC_REFERENCE, ER(ER_CYCLIC_REFERENCE), MYF(0));
+	  return 1;
+	}
       }
     }
     else if (!ref)
@@ -873,6 +892,14 @@ bool Item_ref::fix_fields(THD *thd,TABLE_LIST *tables, Item **reference)
   return 0;
 }
 
+bool Item_ref::check_loop(uint id)
+{
+  DBUG_ENTER("Item_ref::check_loop");
+  if (Item_ident::check_loop(id))
+    DBUG_RETURN(1);
+  DBUG_RETURN((*ref)->check_loop(id));
+}
+
 /*
 ** If item is a const function, calculate it and return a const item
 ** The original item is freed if not returned

sql/item.h

@@ -20,10 +20,11 @@
 #endif
 
 struct st_table_list;
-void item_init(void);				/* Init item functions */
+void item_init(void);			/* Init item functions */
 
 class Item {
-  Item(const Item &);				/* Prevent use of these */
+  uint loop_id;                         /* Used to find selfrefering loops */
+  Item(const Item &);			/* Prevent use of these */
   void operator=(Item &);
 public:
   static void *operator new(size_t size) {return (void*) sql_alloc((uint) size); }
@@ -88,6 +89,8 @@ public:
   virtual CHARSET_INFO *charset() const { return str_value.charset(); };
   virtual bool binary() const { return str_value.charset()->state & MY_CS_BINSORT ? 1 : 0 ; }
   virtual void set_charset(CHARSET_INFO *cs) { str_value.set_charset(cs); }
+  
+  virtual bool check_loop(uint id);
 };
 
 
@@ -434,6 +437,7 @@ public:
   void save_org_in_field(Field *field)	{ (*ref)->save_org_in_field(field); }
   enum Item_result result_type () const { return (*ref)->result_type(); }
   table_map used_tables() const		{ return (*ref)->used_tables(); }
+  bool check_loop(uint id);
 };
 
 

sql/item_cmpfunc.cc

@@ -344,6 +344,14 @@ void Item_func_interval::update_used_tables()
   const_item_cache&=item->const_item();
 }
 
+bool Item_func_interval::check_loop(uint id)
+{
+  DBUG_ENTER("Item_func_interval::check_loop");
+  if (Item_func::check_loop(id))
+    DBUG_RETURN(1);
+  DBUG_RETURN(item->check_loop(id));
+}
+
 void Item_func_between::fix_length_and_dec()
 {
    max_length=1;
@@ -776,6 +784,16 @@ Item_func_case::fix_fields(THD *thd, TABLE_LIST *tables, Item **ref)
   return 0;
 }
 
+bool Item_func_case::check_loop(uint id)
+{
+  DBUG_ENTER("Item_func_case::check_loop");
+  if (Item_func::check_loop(id))
+    DBUG_RETURN(1);
+
+  DBUG_RETURN((first_expr && first_expr->check_loop(id)) ||
+	      (else_expr && else_expr->check_loop(id)));
+}
+
 void Item_func_case::update_used_tables()
 {
   Item_func::update_used_tables();
@@ -1137,6 +1155,20 @@ Item_cond::fix_fields(THD *thd, TABLE_LIST *tables, Item **ref)
   return 0;
 }
 
+bool Item_cond::check_loop(uint id)
+{
+  DBUG_ENTER("Item_cond::check_loop");
+  if (Item_func::check_loop(id))
+    DBUG_RETURN(1);
+  List_iterator<Item> li(list);
+  Item *item;
+  while ((item= li++))
+  {
+    if (item->check_loop(id))
+      DBUG_RETURN(1);
+  }
+  DBUG_RETURN(0);
+}
 
 void Item_cond::split_sum_func(List<Item> &fields)
 {

sql/item_cmpfunc.h

@@ -186,6 +186,7 @@ public:
   ~Item_func_interval() { delete item; }
   const char *func_name() const { return "interval"; }
   void update_used_tables();
+  bool check_loop(uint id);
 };
 
 
@@ -262,6 +263,7 @@ public:
   void print(String *str);
   bool fix_fields(THD *thd, struct st_table_list *tlist, Item **ref);
   Item *find_item(String *str);
+  bool check_loop(uint id);
 };
 
 
@@ -424,6 +426,13 @@ class Item_func_in :public Item_int_func
   enum Functype functype() const { return IN_FUNC; }
   const char *func_name() const { return " IN "; }
   void update_used_tables();
+  bool check_loop(uint id)
+  {
+    DBUG_ENTER("Item_func_in::check_loop");
+    if (Item_func::check_loop(id))
+      DBUG_RETURN(1);
+    DBUG_RETURN(item->check_loop(id));
+  }
 };
 
 
@@ -563,6 +572,7 @@ public:
   void print(String *str);
   void split_sum_func(List<Item> &fields);
   friend int setup_conds(THD *thd,TABLE_LIST *tables,COND **conds);
+  bool check_loop(uint id);
 };
 
 

sql/item_func.cc

@@ -126,6 +126,22 @@ Item_func::fix_fields(THD *thd, TABLE_LIST *tables, Item **ref)
   return 0;
 }
 
+bool Item_func::check_loop(uint id)
+{
+  DBUG_ENTER("Item_func::check_loop");
+  if (Item_result_field::check_loop(id))
+    DBUG_RETURN(1);
+  if (arg_count)
+  {
+    Item **arg,**arg_end;
+    for (arg= args, arg_end= args+arg_count; arg != arg_end; arg++)
+    {
+      if ((*arg)->check_loop(id))
+	DBUG_RETURN(1);
+    }
+  }
+  DBUG_RETURN(0);
+}
 
 void Item_func::split_sum_func(List<Item> &fields)
 {
@@ -2264,6 +2280,19 @@ bool Item_func_match::fix_fields(THD *thd, TABLE_LIST *tlist, Item **ref)
   return 0;
 }
 
+bool Item_func_match::check_loop(uint id)
+{
+  DBUG_ENTER("Item_func_match::check_loop");
+  if (Item_real_func::check_loop(id))
+    DBUG_RETURN(1);
+
+  List_iterator<Item> li(fields);
+  Item *item;
+  while ((item= li++))
+    if (item->check_loop(id))
+      DBUG_RETURN(1);
+  DBUG_RETURN(0);
+}
 
 bool Item_func_match::fix_index()
 {

sql/item_func.h

@@ -128,6 +128,7 @@ public:
   bool is_null() { (void) val_int(); return null_value; }
   friend class udf_handler;
   Field *tmp_table_field(TABLE *t_arg);
+  bool check_loop(uint id);
 };
 
 
@@ -606,6 +607,13 @@ public:
     const_item_cache&=  item->const_item();
     with_sum_func= with_sum_func || item->with_sum_func;
   }
+  bool check_loop(uint id)
+  {
+    DBUG_ENTER("Item_func_field::check_loop");
+    if (Item_int_func::check_loop(id))
+      DBUG_RETURN(1);
+    DBUG_RETURN(item->check_loop(id));
+  }
 };
 
 
@@ -971,6 +979,7 @@ public:
 
   bool fix_index();
   void init_search(bool no_order);
+  bool check_loop(uint id);
 };
 
 

sql/item_strfunc.h

@@ -105,6 +105,13 @@ public:
 	    || Item_func::fix_fields(thd, tlist, ref));
   }
  const char *func_name() const { return "concat_ws"; }
+ bool check_loop(uint id)
+ {
+   DBUG_ENTER("Item_func_concat_ws::check_loop");
+   if (Item_str_func::check_loop(id))
+     DBUG_RETURN(1);
+   DBUG_RETURN(separator->check_loop(id));
+ }
 };
 
 class Item_func_reverse :public Item_str_func
@@ -361,6 +368,13 @@ public:
   void fix_length_and_dec();
   void update_used_tables();
   const char *func_name() const { return "elt"; }
+  bool check_loop(uint id)
+  {
+    DBUG_ENTER("Item_func_elt::check_loop");
+    if (Item_str_func::check_loop(id))
+      DBUG_RETURN(1);
+    DBUG_RETURN(item->check_loop(id));
+  }
 };
 
 
@@ -381,6 +395,13 @@ public:
   void fix_length_and_dec();
   void update_used_tables();
   const char *func_name() const { return "make_set"; }
+  bool check_loop(uint id)
+  {
+    DBUG_ENTER("Item_func_make_set::check_loop");
+    if (Item_str_func::check_loop(id))
+      DBUG_RETURN(1);
+    DBUG_RETURN(item->check_loop(id));
+  }
 };
 
 

sql/item_subselect.cc

@@ -95,6 +95,15 @@ bool Item_subselect::fix_fields(THD *thd, TABLE_LIST *tables, Item **ref)
   return res;
 }
 
+bool Item_subselect::check_loop(uint id)
+{
+  DBUG_ENTER("Item_subselect::check_loop");
+  if (Item_result_field::check_loop(id))
+    DBUG_RETURN(1);
+  
+  DBUG_RETURN(engine->check_loop(id));
+}
+
 void Item_subselect::fix_length_and_dec()
 {
   engine->fix_length_and_dec();
@@ -228,6 +237,7 @@ subselect_single_select_engine::subselect_single_select_engine(THD *thd,
     thd->fatal_error= 1;
     my_message(ER_OUT_OF_RESOURCES, ER(ER_OUT_OF_RESOURCES), MYF(0));
   } 
+  unit->item= item;
   this->select_lex= select_lex;
 }
 
@@ -353,3 +363,18 @@ bool subselect_union_engine::depended()
 {
   return unit->dependent;
 }
+
+bool subselect_single_select_engine::check_loop(uint id)
+{
+  DBUG_ENTER("subselect_single_select_engine::check_loop");
+  DBUG_RETURN(join->check_loop(id));
+}
+
+bool subselect_union_engine::check_loop(uint id)
+{
+  DBUG_ENTER("subselect_union_engine::check_loop");
+  for (SELECT_LEX *sl= unit->first_select(); sl; sl= sl->next_select())
+    if (sl->join && sl->join->check_loop(id))
+      DBUG_RETURN(1);
+  DBUG_RETURN(0);
+}

sql/item_subselect.h

@@ -70,6 +70,7 @@ public:
   bool fix_fields(THD *thd, TABLE_LIST *tables, Item **ref);
   virtual void fix_length_and_dec();
   table_map used_tables() const;
+  bool check_loop(uint id);
 
   friend class select_subselect;
 };
@@ -176,6 +177,7 @@ public:
   virtual uint cols()= 0; /* return number of columnss in select */
   virtual bool depended()= 0; /* depended from outer select */
   enum Item_result type() { return res_type; }
+  virtual bool check_loop(uint id)= 0;
 };
 
 class subselect_single_select_engine: public subselect_engine
@@ -189,11 +191,12 @@ public:
   subselect_single_select_engine(THD *thd, st_select_lex *select,
 				 select_subselect *result,
 				 Item_subselect *item);
-  virtual int prepare();
-  virtual void fix_length_and_dec();
-  virtual int exec();
-  virtual uint cols();
-  virtual bool depended();
+  int prepare();
+  void fix_length_and_dec();
+  int exec();
+  uint cols();
+  bool depended();
+  bool check_loop(uint id);
 };
 
 class subselect_union_engine: public subselect_engine
@@ -204,9 +207,10 @@ public:
 			 st_select_lex_unit *u,
 			 select_subselect *result,
 			 Item_subselect *item);
-  virtual int prepare();
-  virtual void fix_length_and_dec();
-  virtual int exec();
-  virtual uint cols();
-  virtual bool depended();
+  int prepare();
+  void fix_length_and_dec();
+  int exec();
+  uint cols();
+  bool depended();
+  bool check_loop(uint id);
 };

sql/share/czech/errmsg.txt

@@ -252,4 +252,5 @@
 "Subselect returns more than 1 field",
 "Subselect returns more than 1 record",
 "Unknown prepared statement handler (%ld) given to %s",
-"Help database is corrupt or does not exist",
+"Help database is corrupt or does not exist",
\ No newline at end of file
+"Cyclic reference on subqueries",

sql/share/danish/errmsg.txt

@@ -246,4 +246,5 @@
 "Subselect returns more than 1 field",
 "Subselect returns more than 1 record",
 "Unknown prepared statement handler (%ld) given to %s",
-"Help database is corrupt or does not exist",
+"Help database is corrupt or does not exist",
\ No newline at end of file
+"Cyclic reference on subqueries",

sql/share/dutch/errmsg.txt

@@ -254,4 +254,5 @@
 "Subselect returns more than 1 field",
 "Subselect returns more than 1 record",
 "Unknown prepared statement handler (%ld) given to %s",
-"Help database is corrupt or does not exist",
+"Help database is corrupt or does not exist",
\ No newline at end of file
+"Cyclic reference on subqueries",

sql/share/english/errmsg.txt

@@ -243,4 +243,5 @@
 "Subselect returns more than 1 field",
 "Subselect returns more than 1 record",
 "Unknown prepared statement handler (%ld) given to %s",
-"Help database is corrupt or does not exist",
+"Help database is corrupt or does not exist",
\ No newline at end of file
+"Cyclic reference on subqueries",

sql/share/estonian/errmsg.txt

@@ -248,4 +248,5 @@
 "Subselect returns more than 1 field",
 "Subselect returns more than 1 record",
 "Unknown prepared statement handler (%ld) given to %s",
-"Help database is corrupt or does not exist",
+"Help database is corrupt or does not exist",
\ No newline at end of file
+"Cyclic reference on subqueries",

sql/share/french/errmsg.txt

@@ -243,4 +243,5 @@
 "Subselect returns more than 1 field",
 "Subselect returns more than 1 record",
 "Unknown prepared statement handler (%ld) given to %s",
-"Help database is corrupt or does not exist",
+"Help database is corrupt or does not exist",
\ No newline at end of file
+"Cyclic reference on subqueries",

sql/share/german/errmsg.txt

@@ -246,4 +246,5 @@
 "Subselect return more than 1 field",
 "Subselect return more than 1 record",
 "Unknown prepared statement handler (%ld) given to %s",
-"Help database is corrupt or does not exist",
+"Help database is corrupt or does not exist",
\ No newline at end of file
+"Cyclic reference on subqueries",

sql/share/greek/errmsg.txt

@@ -243,4 +243,5 @@
 "Subselect returns more than 1 field",
 "Subselect returns more than 1 record",
 "Unknown prepared statement handler (%ld) given to %s",
-"Help database is corrupt or does not exist",
+"Help database is corrupt or does not exist",
\ No newline at end of file
+"Cyclic reference on subqueries",

sql/share/hungarian/errmsg.txt

@@ -245,4 +245,5 @@
 "Subselect returns more than 1 field",
 "Subselect returns more than 1 record",
 "Unknown prepared statement handler (%ld) given to %s",
-"Help database is corrupt or does not exist",
+"Help database is corrupt or does not exist",
\ No newline at end of file
+"Cyclic reference on subqueries",

sql/share/italian/errmsg.txt

@@ -243,4 +243,5 @@
 "Subselect returns more than 1 field",
 "Subselect returns more than 1 record",
 "Unknown prepared statement handler (%ld) given to %s",
-"Help database is corrupt or does not exist",
+"Help database is corrupt or does not exist",
\ No newline at end of file
+"Cyclic reference on subqueries",

sql/share/japanese/errmsg.txt

@@ -245,4 +245,5 @@
 "Subselect returns more than 1 field",
 "Subselect returns more than 1 record",
 "Unknown prepared statement handler (%ld) given to %s",
-"Help database is corrupt or does not exist",
+"Help database is corrupt or does not exist",
\ No newline at end of file
+"Cyclic reference on subqueries",

sql/share/korean/errmsg.txt

@@ -243,4 +243,5 @@
 "Subselect returns more than 1 field",
 "Subselect returns more than 1 record",
 "Unknown prepared statement handler (%ld) given to %s",
-"Help database is corrupt or does not exist",
+"Help database is corrupt or does not exist",
\ No newline at end of file
+"Cyclic reference on subqueries",

sql/share/norwegian-ny/errmsg.txt

@@ -245,4 +245,5 @@
 "Subselect returns more than 1 field",
 "Subselect returns more than 1 record",
 "Unknown prepared statement handler (%ld) given to %s",
-"Help database is corrupt or does not exist",
+"Help database is corrupt or does not exist",
\ No newline at end of file
+"Cyclic reference on subqueries",

sql/share/norwegian/errmsg.txt

@@ -245,4 +245,5 @@
 "Subselect returns more than 1 field",
 "Subselect returns more than 1 record",
 "Unknown prepared statement handler (%ld) given to %s",
-"Help database is corrupt or does not exist",
+"Help database is corrupt or does not exist",
\ No newline at end of file
+"Cyclic reference on subqueries",

sql/share/polish/errmsg.txt

@@ -247,4 +247,5 @@
 "Subselect returns more than 1 field",
 "Subselect returns more than 1 record",
 "Unknown prepared statement handler (%ld) given to %s",
-"Help database is corrupt or does not exist",
+"Help database is corrupt or does not exist",
\ No newline at end of file
+"Cyclic reference on subqueries",

sql/share/portuguese/errmsg.txt

@@ -243,4 +243,5 @@
 "Subselect returns more than 1 field",
 "Subselect returns more than 1 record",
 "Unknown prepared statement handler (%ld) given to %s",
-"Help database is corrupt or does not exist",
+"Help database is corrupt or does not exist",
\ No newline at end of file
+"Cyclic reference on subqueries",

sql/share/romanian/errmsg.txt

@@ -247,4 +247,5 @@
 "Subselect returns more than 1 field",
 "Subselect returns more than 1 record",
 "Unknown prepared statement handler (%ld) given to %s",
-"Help database is corrupt or does not exist",
+"Help database is corrupt or does not exist",
\ No newline at end of file
+"Cyclic reference on subqueries",

sql/share/russian/errmsg.txt

@@ -246,4 +246,5 @@
 "    ",
 "    ",
 "Unknown prepared statement handler (%ld) given to %s",
-"Help database is corrupt or does not exist",
+"Help database is corrupt or does not exist",
\ No newline at end of file
+"   ",

sql/share/serbian/errmsg.txt

@@ -239,4 +239,5 @@
 "Subselect returns more than 1 field",
 "Subselect returns more than 1 record",
 "Unknown prepared statement handler (%ld) given to %s",
-"Help database is corrupt or does not exist",
+"Help database is corrupt or does not exist",
\ No newline at end of file
+"Cyclic reference on subqueries",

sql/share/slovak/errmsg.txt

@@ -251,4 +251,5 @@
 "Subselect returns more than 1 field",
 "Subselect returns more than 1 record",
 "Unknown prepared statement handler (%ld) given to %s",
-"Help database is corrupt or does not exist",
+"Help database is corrupt or does not exist",
\ No newline at end of file
+"Cyclic reference on subqueries",

sql/share/spanish/errmsg.txt

@@ -244,4 +244,5 @@
 "Subselect returns more than 1 field",
 "Subselect returns more than 1 record",
 "Unknown prepared statement handler (%ld) given to %s",
-"Help database is corrupt or does not exist",
+"Help database is corrupt or does not exist",
\ No newline at end of file
+"Cyclic reference on subqueries",

sql/share/swedish/errmsg.txt

@@ -243,4 +243,5 @@
 "Subselect returns more than 1 field",
 "Subselect returns more than 1 record",
 "Unknown prepared statement handler (%ld) given to %s",
-"Help database is corrupt or does not exist",
+"Help database is corrupt or does not exist",
\ No newline at end of file
+"Cyclic reference on subqueries",

sql/share/ukrainian/errmsg.txt

@@ -248,4 +248,5 @@
 "i  i i 1 ",
 "i  i i 1 ",
 "Unknown prepared statement handler (%ld) given to %s",
-"Help database is corrupt or does not exist",
+"Help database is corrupt or does not exist",
\ No newline at end of file
+"i   i",

sql/sql_class.h

@@ -494,6 +494,7 @@ public:
   uint32     query_length;
   uint32     db_length;
   uint       select_number;             //number of select (used for EXPLAIN)
+  uint       check_loops_counter;       //last id used to check loops
   /* variables.transaction_isolation is reset to this after each commit */
   enum_tx_isolation session_tx_isolation;
   char	     scramble[9];

sql/sql_parse.cc

@@ -2867,7 +2867,8 @@ mysql_init_query(THD *thd)
   lex->select_lex.prev= &lex->unit.slave;
   lex->olap=lex->describe=0;
   lex->derived_tables= false;
-  thd->select_number= lex->select_lex.select_number= 1;
+  thd->check_loops_counter= thd->select_number= 
+    lex->select_lex.select_number= 1;
   thd->free_list= 0;
   thd->total_warn_count=0;			// Warnings for this query
   thd->last_insert_id_used= thd->query_start_used= thd->insert_id_used=0;

sql/sql_select.cc

@@ -1035,6 +1035,24 @@ JOIN::cleanup(THD *thd)
   DBUG_RETURN(error);
 }
 
+bool JOIN::check_loop(uint id)
+{
+  DBUG_ENTER("JOIN::check_loop");
+  Item *item;
+  List_iterator<Item> it(all_fields);
+  DBUG_PRINT("info", ("all_fields:"));
+  while ((item= it++))
+    if (item->check_loop(id))
+      DBUG_RETURN(1);
+  DBUG_PRINT("info", ("where:"));
+  if (select_lex->where && select_lex->where->check_loop(id))
+    DBUG_RETURN(1);
+  DBUG_PRINT("info", ("having:"));
+  if (select_lex->having && select_lex->having->check_loop(id))
+    DBUG_RETURN(1);
+  DBUG_RETURN(0);
+}
+
 int
 mysql_select(THD *thd, TABLE_LIST *tables, List<Item> &fields, COND *conds,
 	     ORDER *order, ORDER *group,Item *having, ORDER *proc_param,

sql/sql_select.h

@@ -244,7 +244,8 @@ class JOIN :public Sql_alloc
   int global_optimize();
   int reinit();
   void exec();
-  int cleanup(THD *thd);  
+  int cleanup(THD *thd);
+  bool check_loop(uint id);
 };