fixed ALL/ANY optimisation with union (BUG#1668)

code cleanup

mysql-test/r/subselect.result

@@ -1489,3 +1489,17 @@ set sort_buffer_size = (select s1 from t1);
 ERROR 21000: Subquery returns more than 1 row
 do (select * from t1);
 drop table t1;
+create table t1 (s1 char);
+insert into t1 values ('e');
+select * from t1 where 'f' > any (select s1 from t1);
+s1
+e
+select * from t1 where 'f' > any (select s1 from t1 union select s1 from t1);
+s1
+e
+explain select * from t1 where 'f' > any (select s1 from t1 union select s1 from t1);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	system	NULL	NULL	NULL	NULL	1	
+2	SUBQUERY	t1	system	NULL	NULL	NULL	NULL	1	
+3	UNION	t1	system	NULL	NULL	NULL	NULL	1	
+drop table t1;

mysql-test/t/subselect.test

@@ -1010,3 +1010,13 @@ insert into t1 values (2);
 set sort_buffer_size = (select s1 from t1);
 do (select * from t1);
 drop table t1;
+
+#
+# optimized ALL/ANY with union
+#
+create table t1 (s1 char);
+insert into t1 values ('e');
+select * from t1 where 'f' > any (select s1 from t1);
+select * from t1 where 'f' > any (select s1 from t1 union select s1 from t1);
+explain select * from t1 where 'f' > any (select s1 from t1 union select s1 from t1);
+drop table t1;

sql/item_subselect.cc

@@ -35,7 +35,7 @@ inline Item * and_items(Item* cond, Item *item)
 }
 
 Item_subselect::Item_subselect():
-  Item_result_field(), engine_owner(1), value_assigned(0), substitution(0),
+  Item_result_field(), value_assigned(0), substitution(0),
   engine(0), used_tables_cache(0), have_to_be_excluded(0),
   const_item_cache(1), engine_changed(0)
 {
@@ -66,7 +66,6 @@ void Item_subselect::init(st_select_lex *select_lex,
 
 Item_subselect::~Item_subselect()
 {
-  if (engine_owner)
   delete engine;
 }
 
@@ -183,7 +182,8 @@ Item_singlerow_subselect::Item_singlerow_subselect(st_select_lex *select_lex)
   DBUG_VOID_RETURN;
 }
 
-Item_maxmin_subselect::Item_maxmin_subselect(st_select_lex *select_lex,
+Item_maxmin_subselect::Item_maxmin_subselect(Item_subselect *parent,
+					     st_select_lex *select_lex,
 					     bool max)
   :Item_singlerow_subselect()
 {
@@ -192,6 +192,14 @@ Item_maxmin_subselect::Item_maxmin_subselect(st_select_lex *select_lex,
   max_columns= 1;
   maybe_null= 1;
   max_columns= 1;
+
+  /*
+    Following information was collected during performing fix_fields()
+    of Items belonged to subquery, which will be not repeated
+  */
+  used_tables_cache= parent->get_used_tables_cache();
+  const_item_cache= parent->get_const_item_cache();
+  
   DBUG_VOID_RETURN;
 }
 
@@ -527,9 +535,16 @@ Item_in_subselect::single_value_transformer(JOIN *join,
        func == &Item_bool_func2::ge_creator ||
        func == &Item_bool_func2::le_creator))
   {
+    if (substitution)
+    {
+      // It is second (third, ...) SELECT of UNION => All is done
+      DBUG_RETURN(RES_OK);
+    }
+
     Item *subs;
     if (!select_lex->group_list.elements &&
-	!select_lex->with_sum_func)
+	!select_lex->with_sum_func &&
+	!(select_lex->next_select()))
     {
       Item *item;
       subs_type type= substype();
@@ -565,7 +580,7 @@ Item_in_subselect::single_value_transformer(JOIN *join,
       // remove LIMIT placed  by ALL/ANY subquery
       select_lex->master_unit()->global_parameters->select_limit=
 	HA_POS_ERROR;
-      subs= new Item_maxmin_subselect(select_lex,
+      subs= new Item_maxmin_subselect(this, select_lex,
 				      (func == &Item_bool_func2::le_creator ||
 				       func == &Item_bool_func2::lt_creator));
     }

sql/item_subselect.h

@@ -33,7 +33,6 @@ typedef Item_bool_func2* (*compare_func_creator)(Item*, Item*);
 
 class Item_subselect :public Item_result_field
 {
-  my_bool engine_owner; /* Is this item owner of engine */
   my_bool value_assigned; /* value already assigned to subselect */
 protected:
   /* thread handler, will be assigned in fix_fields only */
@@ -90,6 +89,8 @@ public:
   virtual void fix_length_and_dec();
   table_map used_tables() const;
   bool const_item() const;
+  inline table_map get_used_tables_cache() { return used_tables_cache; }
+  inline bool get_const_item_cache() { return const_item_cache; }
   void update_used_tables();
   void print(String *str)
   {
@@ -144,10 +145,11 @@ public:
 };
 
 /* used in static ALL/ANY optimisation */
-class Item_maxmin_subselect: public Item_singlerow_subselect
+class Item_maxmin_subselect :public Item_singlerow_subselect
 {
 public:
-  Item_maxmin_subselect(st_select_lex *select_lex, bool max);
+  Item_maxmin_subselect(Item_subselect *parent,
+			st_select_lex *select_lex, bool max);
 };
 
 /* exists subselect */

sql/sql_union.cc

@@ -119,13 +119,18 @@ int st_select_lex_unit::prepare(THD *thd, select_result *sel_result,
   SELECT_LEX *select_cursor,*sl;
   DBUG_ENTER("st_select_lex_unit::prepare");
 
+  /*
+    result object should be reassigned even if preparing already done for
+    max/min subquery (ALL/ANY optimization)
+  */
+  result= sel_result;
+
   if (prepared)
     DBUG_RETURN(0);
   prepared= 1;
   res= 0;
   found_rows_for_union= first_select_in_union()->options & OPTION_FOUND_ROWS;
   TMP_TABLE_PARAM tmp_table_param;
-  result= sel_result;
   t_and_f= tables_and_fields_initied;
   
   bzero((char *)&tmp_table_param,sizeof(TMP_TABLE_PARAM));