new SELECT_LEX structure

mysql-test/r/derived.result

-drop table if exists t1,t2;
+drop table if exists t1,t2,t3;
 CREATE TABLE t1 (a int not null, b char (10) not null);
 insert into t1 values(1,'a'),(2,'b'),(3,'c'),(3,'c');
 CREATE TABLE t2 (a int not null, b char (10) not null);
@@ -7,4 +7,10 @@ select t1.a,t3.y from t1,(select a as y from t2  where b='c') as t3  where t1.a
 a	y
 3	3
 3	3
-drop table if exists  t1.t2;
+CREATE TABLE t3 (a int not null, b char (10) not null);
+insert into t3 values (3,'f'),(4,'y'),(5,'z'),(6,'c');
+select t1.a,t4.y from t1,(select t2.a as y from t2,(select t3.b from t3 where t3.a>3) as t5  where t2.b=t5.b) as t4  where t1.a = t4.y;
+a	y
+3	3
+3	3
+drop table if exists  t1.t2,t3;

mysql-test/t/derived.test

-drop table if exists t1,t2;
+drop table if exists t1,t2,t3;
 CREATE TABLE t1 (a int not null, b char (10) not null);
 insert into t1 values(1,'a'),(2,'b'),(3,'c'),(3,'c');
 CREATE TABLE t2 (a int not null, b char (10) not null);
 insert into t2 values (3,'c'),(4,'d'),(5,'f'),(6,'e');
 select t1.a,t3.y from t1,(select a as y from t2  where b='c') as t3  where t1.a = t3.y;
-drop table if exists  t1.t2;
+CREATE TABLE t3 (a int not null, b char (10) not null);
\ No newline at end of file
+insert into t3 values (3,'f'),(4,'y'),(5,'z'),(6,'c');
+select t1.a,t4.y from t1,(select t2.a as y from t2,(select t3.b from t3 where t3.a>3) as t5  where t2.b=t5.b) as t4  where t1.a = t4.y;
+drop table if exists  t1.t2,t3;

sql/mysql_priv.h

@@ -291,7 +291,7 @@ bool mysql_rename_tables(THD *thd, TABLE_LIST *table_list);
 bool mysql_change_db(THD *thd,const char *name);
 void mysql_parse(THD *thd,char *inBuf,uint length);
 void mysql_init_select(LEX *lex);
-bool mysql_new_select(LEX *lex);
+bool mysql_new_select(LEX *lex, bool move_down);
 void mysql_init_multi_delete(LEX *lex);
 void init_max_user_conn(void);
 void free_max_user_conn(void);
@@ -360,8 +360,8 @@ int handle_select(THD *thd, LEX *lex, select_result *result);
 int mysql_select(THD *thd,TABLE_LIST *tables,List<Item> &list,COND *conds,
 		 ORDER *order, ORDER *group,Item *having,ORDER *proc_param,
 		 ulong select_type,select_result *result);
-int mysql_union(THD *thd,LEX *lex,select_result *result);
-int mysql_derived(THD *thd,LEX *lex,SELECT_LEX *s, TABLE_LIST *t);
+int mysql_union(THD *thd, LEX *lex,select_result *result);
+int mysql_derived(THD *thd, LEX *lex, SELECT_LEX_UNIT *s, TABLE_LIST *t);
 Field *create_tmp_field(THD *thd, TABLE *table,Item *item, Item::Type type,
 			Item_result_field ***copy_func, Field **from_field,
 			bool group,bool modify_item);

sql/sql_class.h

@@ -706,19 +706,28 @@ class Table_ident :public Sql_alloc {
  public:
   LEX_STRING db;
   LEX_STRING table;
-  SELECT_LEX *sel;
-  inline Table_ident(LEX_STRING db_arg,LEX_STRING table_arg,bool force)
-    :table(table_arg), sel((SELECT_LEX *)0)
+  SELECT_LEX_UNIT *sel;
+  inline Table_ident(LEX_STRING db_arg, LEX_STRING table_arg, bool force)
+    :table(table_arg), sel((SELECT_LEX_UNIT *)0)
   {
     if (!force && (current_thd->client_capabilities & CLIENT_NO_SCHEMA))
       db.str=0;
     else
       db= db_arg;
   }
-  inline Table_ident(LEX_STRING table_arg) :table(table_arg), sel((SELECT_LEX *)0) {db.str=0;}
-  inline Table_ident(SELECT_LEX *s) : sel(s) {db.str=0; table.str=(char *)""; table.length=0;}
+  inline Table_ident(LEX_STRING table_arg) 
+    :table(table_arg), sel((SELECT_LEX_UNIT *)0)
+  {
+    db.str=0;
+  }
+  inline Table_ident(SELECT_LEX_UNIT *s) : sel(s) 
+  {
+    db.str=0; table.str=(char *)""; table.length=0;
+  }
   inline void change_db(char *db_name)
-  { db.str= db_name; db.length=(uint) strlen(db_name); }
+  {
+    db.str= db_name; db.length= (uint) strlen(db_name);
+  }
 };
 
 // this is needed for user_vars hash

sql/sql_derived.cc

@@ -28,21 +28,25 @@
 static const char *any_db="*any*";	// Special symbol for check_access
 
 
-int mysql_derived(THD *thd, LEX *lex,SELECT_LEX *s, TABLE_LIST *t)
+int mysql_derived(THD *thd, LEX *lex, SELECT_LEX_UNIT *s, TABLE_LIST *t)
 {
-  SELECT_LEX *sl=s;
+  /*
+    TODO: make derived tables with union inside (now only 1 SELECT may be
+    procesed)
+  */
+  SELECT_LEX *sl= (SELECT_LEX*)s->slave;
   List<Item> item_list;
   TABLE *table;
   int res;
   select_union *derived_result;
-  TABLE_LIST *tables=(TABLE_LIST *)sl->table_list.first;
+  TABLE_LIST *tables= (TABLE_LIST *)sl->table_list.first;
   TMP_TABLE_PARAM tmp_table_param;
   DBUG_ENTER("mysql_derived");
   
   if (tables)
-    res=check_table_access(thd,SELECT_ACL, tables);
+    res= check_table_access(thd,SELECT_ACL, tables);
   else
-    res=check_access(thd, SELECT_ACL, any_db);
+    res= check_access(thd, SELECT_ACL, any_db);
   if (res)
     DBUG_RETURN(-1);
 
@@ -52,7 +56,7 @@ int mysql_derived(THD *thd, LEX *lex,SELECT_LEX *s, TABLE_LIST *t)
   {
     if (cursor->derived)
     {
-      res=mysql_derived(thd,lex,(SELECT_LEX *)cursor->derived,cursor);
+      res=mysql_derived(thd, lex, (SELECT_LEX_UNIT *)cursor->derived, cursor);
       if (res) DBUG_RETURN(res);
     }
   }
@@ -103,9 +107,8 @@ int mysql_derived(THD *thd, LEX *lex,SELECT_LEX *s, TABLE_LIST *t)
 	{
 	  t->real_name=table->real_name;
 	  t->table=table;
-	  sl->prev->next=sl->next;
+	  sl->exclude();
 	  t->derived=(SELECT_LEX *)0; // just in case ...
-	  if (!sl->next) lex->last_select = sl;
 	}
       }
       delete derived_result;

sql/sql_lex.cc

@@ -879,3 +879,118 @@ int yylex(void *arg)
     }
   }
 }
+
+/*
+  st_select_lex structures initialisations
+*/
+
+void st_select_lex_node::init_query()
+{
+  next= master= slave= link_next= 0;
+  prev= link_prev= 0;
+}
+
+void st_select_lex_node::init_select()
+{
+  order_list.elements= 0;
+  order_list.first= 0;
+  order_list.next= (byte**) &order_list.first;
+  select_limit= offset_limit= 0; 
+}
+
+void st_select_lex_unit::init_query()
+{
+  st_select_lex_node::init_query();
+  global_parameters= this;
+  select_limit_cnt= offset_limit_cnt= 0;
+}
+
+void st_select_lex::init_query()
+{
+  st_select_lex_node::init_query();
+  table_list.elements= 0;
+  table_list.first= 0; 
+  table_list.next= (byte**) &table_list.first;
+  item_list.empty();
+}
+
+void st_select_lex::init_select()
+{
+  st_select_lex_node::init_select();
+  group_list.elements= 0;
+  group_list.first= 0;
+  group_list.next= (byte**) &group_list.first;
+  options= 0;
+  where= having= 0;
+  when_list.empty(); 
+  expr_list.empty();
+  interval_list.empty(); 
+  use_index.empty();
+  ftfunc_list.empty();
+  linkage=UNSPECIFIED_TYPE;
+}
+
+/*
+  st_select_lex structures linking
+*/
+
+/* include on level down */
+void st_select_lex_node::include_down(st_select_lex_node *upper)
+{
+  if ((next= upper->slave))
+    next->prev= &next;
+  prev= &upper->slave;
+  upper->slave= this;
+  master= upper;
+}
+
+/* include neighbour (on same level) */
+void st_select_lex_node::include_neighbour(st_select_lex_node *before)
+{
+  if ((next= before->next))
+    next->prev= &next;
+  prev= &before->next;
+  before->next= this;
+  master= before->master;
+}
+
+/* including in global SELECT_LEX list */
+void st_select_lex_node::include_global(st_select_lex_node **plink)
+{
+  if ((link_next= *plink))
+    link_next->link_prev= &link_next;
+  link_prev= plink;
+  *plink= this;
+}
+
+//excluding from global list (internal function)
+void st_select_lex_node::fast_exclude()
+{
+  if(link_prev)
+  {
+    if ((*link_prev= link_next))
+      link_next->link_prev= link_prev;
+    // Remove slave structure
+    for (; slave; slave= slave->next)
+      slave->fast_exclude();
+  }
+}
+
+/*
+  excluding select_lex structure (except first (first select can't be
+  deleted, because it is most upper select))
+*/
+void st_select_lex_node::exclude()
+{
+  //exclude from global list
+  fast_exclude();
+  //exclude from other structures
+  if ((*prev= next))
+    next->prev= prev;
+  /* 
+     We do not need following statements, because prev pointer of first 
+     list element point to master->slave
+     if (master->slave == this)
+       master->slave= next;
+  */
+}

sql/sql_lex.h

@@ -103,28 +103,143 @@ typedef struct st_lex_master_info
 } LEX_MASTER_INFO;
 
 
-enum sub_select_type {UNSPECIFIED_TYPE,UNION_TYPE, INTERSECT_TYPE, EXCEPT_TYPE, NOT_A_SELECT, DERIVED_TABLE_TYPE};
+enum sub_select_type {UNSPECIFIED_TYPE,UNION_TYPE, INTERSECT_TYPE,
+		      EXCEPT_TYPE, GLOBAL_OPTIONS_TYPE, DERIVED_TABLE_TYPE};
 
-/* The state of the lex parsing for selects */
+/* 
+  The state of the lex parsing for selects 
    
-typedef struct st_select_lex {
+   All select describing structures linked with following pointers:
+   - list of neighbors (next/prev) (prev of first element point to slave 
+     pointer of upper structure)
+     - one level units for unit (union) structure
+     - member of one union(unit) for ordinary select_lex
+   - pointer to master
+     - outer select_lex for unit (union)
+     - unit structure for ordinary select_lex
+   - pointer to slave
+     - first list element of select_lex belonged to this unit for unit
+     - first unit in list of units that belong to this select_lex (as
+       subselects or derived tables) for ordinary select_lex
+   - list of all select_lex (for group operation like correcting list of opened
+     tables)
+   for example for following query:
+
+   select *
+     from table1
+     where table1.field IN (select * from table1_1_1 union
+                            select * from table1_1_2)
+     union
+   select *
+     from table2
+     where table2.field=(select (select f1 from table2_1_1_1_1
+                                   where table2_1_1_1_1.f2=table2_1_1.f3)
+                           from table2_1_1
+                           where table2_1_1.f1=table2.f2)
+     union
+   select * from table3;
+
+   we will have following structure:
+
+
+     main unit
+     select1 select2 select3
+     |^^     |^
+    s|||     ||master
+    l|||     |+---------------------------------+
+    a|||     +---------------------------------+|
+    v|||master                         slave   ||
+    e||+-------------------------+             ||
+     V|            neighbor      |             V|
+     unit 1.1<==================>unit1.2       unit2.1
+     select1.1.1 select 1.1.2    select1.2.1   select2.1.1 select2.1.2
+                                               |^
+                                               ||
+                                               V|
+                                               unit2.1.1.1
+                                               select2.1.1.1.1
+
+
+   relation in main unit will be following:
+                          
+         main unit
+         |^^^
+         ||||
+         |||+------------------------------+
+         ||+--------------+                |
+    slave||master         |                |
+         V|      neighbor |       neighbor |
+         select1<========>select2<========>select3
+
+    list of all select_lex will be following (as it will be constructed by
+    parser):
+
+    select1->select2->select3->select2.1.1->select 2.1.2->select2.1.1.1.1-+
+                                                                          |
+    +---------------------------------------------------------------------+
+    |
+    +->select1.1.1->select1.1.2
+
+*/
+
+/* 
+    Base class for st_select_lex (SELECT_LEX) & 
+    st_select_lex_unit (SELECT_LEX_UNIT)
+*/
+struct st_select_lex_node {
   enum sub_select_type linkage;
-  char *db,*db1,*table1,*db2,*table2;		/* For outer join using .. */
-  Item *where,*having;
-  ha_rows select_limit,offset_limit;
+  st_select_lex_node *next, **prev,   /* neighbor list */
+    *master, *slave,                  /* vertical links */
+    *link_next, **link_prev;          /* list of whole SELECT_LEX */
+  SQL_LIST order_list;                /* ORDER clause */
+  ha_rows select_limit, offset_limit; /* LIMIT clause parameters */
+  void init_query();
+  void init_select();
+  void include_down(st_select_lex_node *upper);
+  void include_neighbour(st_select_lex_node *before);
+  void include_global(st_select_lex_node **plink);
+  void exclude();
+private:
+  void fast_exclude();
+};
+
+/* 
+   SELECT_LEX_UNIT - unit of selects (UNION, INTERSECT, ...) group 
+   SELECT_LEXs
+*/
+struct st_select_lex_unit: public st_select_lex_node {
+  /*
+    Pointer to 'last' select or pointer to unit where stored
+    global parameters for union
+  */
+  st_select_lex_node *global_parameters;
+  /* LIMIT clause runtime counters */
+  ha_rows select_limit_cnt, offset_limit_cnt;
+  void init_query();
+};
+typedef struct st_select_lex_unit SELECT_LEX_UNIT;
+
+/*
+  SELECT_LEX - store information of parsed SELECT_LEX statment
+*/
+struct st_select_lex: public st_select_lex_node {
+  char *db, *db1, *table1, *db2, *table2;      	/* For outer join using .. */
+  Item *where, *having;                         /* WHERE & HAVING clauses */
   ulong options;
   List<List_item>     expr_list;
-  List<List_item>     when_list;
-  SQL_LIST	      order_list,table_list,group_list;
-  List<Item>          item_list;
-  List<String>        interval_list,use_index, *use_index_ptr,
+  List<List_item>     when_list;                /* WHEN clause */
+  SQL_LIST	      table_list, group_list;   /* FROM & GROUP BY clauses */
+  List<Item>          item_list; /* list of fields & expressions */
+  List<String>        interval_list, use_index, *use_index_ptr,
 		      ignore_index, *ignore_index_ptr;
   List<Item_func_match> ftfunc_list;
   uint in_sum_expr, sort_default;
-  bool	create_refs, braces;
-  st_select_lex *next, *prev;
-} SELECT_LEX;
-
+  bool	create_refs, 
+    braces; /* SELECT ... UNION (SELECT ... ) <- this braces */
+  void init_query();
+  void init_select();
+};
+typedef struct st_select_lex SELECT_LEX;
 
 class Set_option :public Sql_alloc {
 public:
@@ -137,13 +252,15 @@ public:
     :name(par_name), item(par_item), name_length(length), type(par_type) {}
 };
 
-
 /* The state of the lex parsing. This is saved in the THD struct */
 
 typedef struct st_lex {
   uint	 yylineno,yytoklen;			/* Simulate lex */
   LEX_YYSTYPE yylval;
-  SELECT_LEX select_lex, *select, *last_select;
+  SELECT_LEX_UNIT unit;                         /* most upper unit */
+  SELECT_LEX select_lex,                        /* first SELECT_LEX */
+    /* current SELECT_LEX in parsing */
+    *select;
   uchar *ptr,*tok_start,*tok_end,*end_of_query;
   char *length,*dec,*change,*name;
   char *backup_dir;				/* For RESTORE/BACKUP */

sql/sql_parse.cc

@@ -1240,8 +1240,10 @@ mysql_execute_command(void)
   {
     for (TABLE_LIST *cursor= tables;
 	 cursor;
-	 cursor=cursor->next)
-      if (cursor->derived && mysql_derived(thd,lex,(SELECT_LEX *)cursor->derived,cursor))
+	 cursor= cursor->next)
+      if (cursor->derived && mysql_derived(thd, lex,
+					   (SELECT_LEX_UNIT *)cursor->derived,
+					   cursor))
 	DBUG_VOID_RETURN;
   }
   if ((lex->select_lex.next && create_total_list(thd,lex,&tables)) ||
@@ -2664,18 +2666,19 @@ static void
 mysql_init_query(THD *thd)
 {
   DBUG_ENTER("mysql_init_query");
-  thd->lex.select_lex.item_list.empty();
+  thd->lex.unit.init_query();
+  thd->lex.select_lex.init_query();
+  thd->lex.unit.slave= &thd->lex.select_lex;
+  thd->lex.select_lex.master= &thd->lex.unit;
+  thd->lex.select_lex.prev= &thd->lex.unit.slave;
   thd->lex.value_list.empty();
-  thd->lex.select_lex.table_list.elements=0;
-  thd->free_list=0;  thd->lex.union_option=0;
-  thd->lex.select = thd->lex.last_select = &thd->lex.select_lex;
-  thd->lex.select_lex.table_list.first=0;
-  thd->lex.select_lex.table_list.next= (byte**) &thd->lex.select_lex.table_list.first;
-  thd->lex.select_lex.next=0;
-  thd->fatal_error=0;				// Safety
-  thd->last_insert_id_used=thd->query_start_used=thd->insert_id_used=0;
-  thd->sent_row_count=thd->examined_row_count=0;
-  thd->safe_to_cache_query=1;
+  thd->free_list= 0;
+  thd->lex.union_option= 0;
+  thd->lex.select= &thd->lex.select_lex;
+  thd->fatal_error= 0;				// Safety
+  thd->last_insert_id_used= thd->query_start_used= thd->insert_id_used=0;
+  thd->sent_row_count= thd->examined_row_count= 0;
+  thd->safe_to_cache_query= 1;
   DBUG_VOID_RETURN;
 }
 
@@ -2683,53 +2686,52 @@ void
 mysql_init_select(LEX *lex)
 {
   SELECT_LEX *select_lex = lex->select;
-  select_lex->where=select_lex->having=0;
+  select_lex->init_select();
   select_lex->select_limit=lex->thd->default_select_limit;
   select_lex->offset_limit=0;
-  select_lex->options=0;
-  select_lex->linkage=UNSPECIFIED_TYPE;
   lex->exchange = 0;
   lex->proc_list.first=0;
-  select_lex->order_list.elements=select_lex->group_list.elements=0;
-  select_lex->order_list.first=0;
-  select_lex->order_list.next= (byte**) &select_lex->order_list.first;
-  select_lex->group_list.first=0;
-  select_lex->group_list.next= (byte**) &select_lex->group_list.first;
-  select_lex->next = select_lex->prev = (SELECT_LEX *)NULL; 
 }
 
 bool
-mysql_new_select(LEX *lex)
+mysql_new_select(LEX *lex, bool move_down)
 {
   SELECT_LEX *select_lex = (SELECT_LEX *) lex->thd->calloc(sizeof(SELECT_LEX));
   if (!select_lex)
     return 1;
-  lex->select=lex->last_select;
-  lex->select->next=select_lex; 
-  lex->select=lex->last_select=select_lex;
-  select_lex->table_list.next= (byte**) &select_lex->table_list.first;
-  select_lex->item_list.empty();
-  select_lex->when_list.empty(); 
-  select_lex->expr_list.empty();
-  select_lex->interval_list.empty(); 
-  select_lex->use_index.empty();
-  select_lex->ftfunc_list.empty();
+  select_lex->init_query();
+  select_lex->init_select();
+  if (move_down)
+  {
+    /* first select_lex of subselect or derived table */
+    SELECT_LEX_UNIT *unit= 
+      (SELECT_LEX_UNIT *) lex->thd->calloc(sizeof(SELECT_LEX_UNIT));
+    if (!unit)
+      return 1;
+    unit->init_query();
+    unit->init_select();
+    unit->include_down(lex->select);
+    select_lex->include_down(unit);
+  }
+  else
+    select_lex->include_neighbour(lex->select);
+    
+  select_lex->include_global(&lex->select->link_next);
+  lex->select= select_lex;
   return 0;
 }
 
 void mysql_init_multi_delete(LEX *lex)
 {
-  lex->sql_command =  SQLCOM_DELETE_MULTI;
+  lex->sql_command=  SQLCOM_DELETE_MULTI;
   mysql_init_select(lex);
-  lex->select->select_limit=HA_POS_ERROR;
-  lex->auxilliary_table_list=lex->select_lex.table_list;
-  lex->select->table_list.elements=0; 
-  lex->select->table_list.first=0;
-  lex->select->table_list.next= (byte**) &(lex->select->table_list.first);
+  lex->select->select_limit= HA_POS_ERROR;
+  lex->auxilliary_table_list= lex->select_lex.table_list;
+  lex->select->init_query();
 }
 
 void
-mysql_parse(THD *thd,char *inBuf,uint length)
+mysql_parse(THD *thd, char *inBuf, uint length)
 {
   DBUG_ENTER("mysql_parse");
 
@@ -3159,7 +3161,7 @@ TABLE_LIST *add_table_to_list(Table_ident *table, LEX_STRING *alias,
   ptr->real_name_length=table->table.length;
   ptr->lock_type=flags;
   ptr->updating=updating;
-  ptr->derived=(SELECT_LEX *)table->sel;
+  ptr->derived= (SELECT_LEX_UNIT *) table->sel;
   if (use_index)
     ptr->use_index=(List<String> *) thd->memdup((gptr) use_index,
 					       sizeof(*use_index));
@@ -3204,8 +3206,8 @@ static bool create_total_list(THD *thd, LEX *lex, TABLE_LIST **result)
   SELECT_LEX *sl;
   TABLE_LIST **new_table_list= result, *aux;
 
-  *new_table_list=0;				// end result list
-  for (sl= &lex->select_lex; sl; sl=sl->next)
+  *new_table_list= 0;				// end result list
+  for (sl= &lex->select_lex; sl; sl= (SELECT_LEX *) sl->next)
   {
     if (sl->order_list.first && sl->next && !sl->braces)
     {

sql/sql_union.cc

@@ -43,8 +43,8 @@ int mysql_union(THD *thd, LEX *lex,select_result *result)
   /* Fix tables 'to-be-unioned-from' list to point at opened tables */
   last_sl= &lex->select_lex;
   for (sl= last_sl;
-       sl && sl->linkage != NOT_A_SELECT;
-       last_sl=sl, sl=sl->next)
+       sl && sl->linkage != GLOBAL_OPTIONS_TYPE;
+       last_sl= sl, sl= (SELECT_LEX *) sl->next)
   {
     for (TABLE_LIST *cursor= (TABLE_LIST *)sl->table_list.first;
 	 cursor;
@@ -133,7 +133,7 @@ int mysql_union(THD *thd, LEX *lex,select_result *result)
   }
   union_result->save_time_stamp=!describe;
 
-  for (sl= &lex->select_lex; sl; sl=sl->next)
+  for (sl= &lex->select_lex; sl; sl= (SELECT_LEX*) sl->next)
   {
     lex->select=sl;
     thd->offset_limit=sl->offset_limit;
@@ -143,14 +143,18 @@ int mysql_union(THD *thd, LEX *lex,select_result *result)
     if (thd->select_limit == HA_POS_ERROR)
       sl->options&= ~OPTION_FOUND_ROWS;
 
-    res=mysql_select(thd, (describe && sl->linkage==NOT_A_SELECT) ? first_table :  (TABLE_LIST*) sl->table_list.first,
+    res= mysql_select(thd, 
+		      (describe && sl->linkage==GLOBAL_OPTIONS_TYPE) ? 
+		      first_table :  (TABLE_LIST*) sl->table_list.first,
 		      sl->item_list,
 		      sl->where,
-		     (sl->braces) ? (ORDER *)sl->order_list.first : (ORDER *) 0,
+		      (sl->braces) ? 
+		      (ORDER *)sl->order_list.first : (ORDER *) 0,
 		      (ORDER*) sl->group_list.first,
 		      sl->having,
 		      (ORDER*) NULL,
-		     sl->options | thd->options | SELECT_NO_UNLOCK | ((describe) ? SELECT_DESCRIBE : 0),
+		      sl->options | thd->options | 
+		      SELECT_NO_UNLOCK | ((describe) ? SELECT_DESCRIBE : 0),
 		      union_result);
     if (res)
       goto exit;

sql/sql_yacc.yy

@@ -2155,21 +2155,22 @@ join_table:
         | '(' SELECT_SYM select_part3 ')' opt_table_alias 
 	{
 	  LEX *lex=Lex;
-	  lex->select=lex->select->prev;
-	  if (!($$=add_table_to_list(new Table_ident(Lex->last_select),$5,0,TL_UNLOCK)))
+	  SELECT_LEX_UNIT *unit= (SELECT_LEX_UNIT*) lex->select->master;
+	  lex->select= (SELECT_LEX*) unit->master;
+	  if (!($$= add_table_to_list(new Table_ident(unit),
+	                              $5,0,TL_UNLOCK)))
 	    YYABORT;
 	}
 
 select_part3:
         {
-	  LEX *lex=Lex;
-	  lex->derived_tables=true;
-	  SELECT_LEX *tmp=lex->select;
-	  if (lex->select->linkage == NOT_A_SELECT || mysql_new_select(lex))
+	  LEX *lex= Lex;
+	  lex->derived_tables= true;
+	  if (lex->select->linkage == GLOBAL_OPTIONS_TYPE || 
+              mysql_new_select(lex, 1))
 	    YYABORT;
 	  mysql_init_select(lex);
-	  lex->select->linkage=DERIVED_TABLE_TYPE;
-	  lex->select->prev=tmp;
+	  lex->select->linkage= DERIVED_TABLE_TYPE;
 	}
         select_options select_item_list select_intoto
 
@@ -3809,7 +3810,8 @@ union_list:
        net_printf(&lex->thd->net, ER_WRONG_USAGE,"UNION","INTO");
        YYABORT;
     } 
-    if (lex->select->linkage == NOT_A_SELECT || mysql_new_select(lex))
+    if (lex->select->linkage == GLOBAL_OPTIONS_TYPE || 
+	mysql_new_select(lex, 0))
       YYABORT;
     lex->select->linkage=UNION_TYPE;
   } 
@@ -3824,10 +3826,10 @@ optional_order_or_limit:
   |
   {
     LEX *lex=Lex;
-    if (!lex->select->braces || mysql_new_select(lex))
+    if (!lex->select->braces || mysql_new_select(lex, 0))
      YYABORT;
     mysql_init_select(lex);
-    lex->select->linkage=NOT_A_SELECT;
+    lex->select->linkage= GLOBAL_OPTIONS_TYPE;
     lex->select->select_limit=lex->thd->default_select_limit;
   }
   opt_order_clause limit_clause

sql/table.h

@@ -142,7 +142,7 @@ typedef struct st_table_list {
   Item		*on_expr;		 /* Used with outer join */
   struct st_table_list *natural_join;	 /* natural join on this table*/
   /* ... join ... USE INDEX ... IGNORE INDEX */
-  List<String>	*use_index,*ignore_index; 
+  List<String>	*use_index, *ignore_index; 
   TABLE		*table;
   GRANT_INFO	grant;
   thr_lock_type lock_type;
@@ -150,7 +150,7 @@ typedef struct st_table_list {
   bool		straight;		 /* optimize with prev table */
   bool          updating;                /* for replicate-do/ignore table */
   bool		shared;			 /* Used twice in union */
-  void    *derived;
+  void          *derived;                /* SELECT_LEX_UNIT of derived table */
 } TABLE_LIST;
 
 typedef struct st_changed_table_list {