removed incorrect error message about aggregate functions

improved mechanisn of detection posibility to be NULL for single row queries
switched off substitution optimisation for single row subqueries in PS due to problem in resolving substituted expressions
(changes to make subselects test working with PS protocol)


mysql-test/r/subselect.result:
  removed incorrect error message about aggregate functions
  improved mechanisn of detection posibility to be NULL for single row queries
mysql-test/t/subselect.test:
  removed incorrect error message about aggregate functions
sql/item_subselect.cc:
  removed incorrect error message about aggregate functions
  switched off substitution optimisation for single row subqueries in PS due to problem in resolving substituted expressions
  improved mechanisn of detection posibility to be NULL for single row queries
sql/item_subselect.h:
  new method to help in NULL ability detection

mysql-test/r/subselect.result

@@ -55,7 +55,7 @@ SELECT 1 FROM (SELECT 1 as a) as b HAVING (SELECT a)=1;
 1
 1
 SELECT (SELECT 1), a;
-ERROR 42S22: Unknown column 'a' in 'checking transformed subquery'
+ERROR 42S22: Unknown column 'a' in 'field list'
 SELECT 1 as a FROM (SELECT 1) as b HAVING (SELECT a)=1;
 a
 1
@@ -999,7 +999,9 @@ drop table t1, t2;
 CREATE TABLE `t1` (`i` int(11) NOT NULL default '0',PRIMARY KEY  (`i`)) ENGINE=MyISAM CHARSET=latin1;
 INSERT INTO t1 VALUES (1);
 UPDATE t1 SET i=i+1 WHERE i=(SELECT MAX(i));
-ERROR HY000: Invalid use of group function
+select * from t1;
+i
+1
 drop table t1;
 CREATE TABLE t1 (a int(1));
 EXPLAIN EXTENDED SELECT (SELECT RAND() FROM t1) FROM t1;
@@ -1084,7 +1086,7 @@ SHOW CREATE TABLE t1;
 Table	Create Table
 t1	CREATE TABLE `t1` (
   `a` bigint(20) NOT NULL default '0',
-  `(SELECT a)` bigint(20) default NULL
+  `(SELECT a)` bigint(20) NOT NULL default '0'
 ) ENGINE=MyISAM DEFAULT CHARSET=latin1
 drop table t1;
 CREATE TABLE t1 SELECT * FROM (SELECT 1 as a,(SELECT a+0)) a;
@@ -1102,7 +1104,7 @@ a
 SHOW CREATE TABLE t1;
 Table	Create Table
 t1	CREATE TABLE `t1` (
-  `a` bigint(20) default NULL
+  `a` bigint(20) NOT NULL default '0'
 ) ENGINE=MyISAM DEFAULT CHARSET=latin1
 drop table t1;
 create table t1 (a int);
@@ -1186,11 +1188,12 @@ PRIMARY KEY  (`i`)
 ) ENGINE=MyISAM CHARSET=latin1;
 INSERT INTO t1 VALUES (1);
 UPDATE t1 SET i=i+(SELECT MAX(i) FROM (SELECT 1) t) WHERE i=(SELECT MAX(i));
-ERROR HY000: Invalid use of group function
 UPDATE t1 SET i=i+1 WHERE i=(SELECT MAX(i));
-ERROR HY000: Invalid use of group function
 UPDATE t1 SET t.i=i+(SELECT MAX(i) FROM (SELECT 1) t);
 ERROR 42S02: Unknown table 't' in field list
+select * from t1;
+i
+1
 drop table t1;
 CREATE TABLE t1 (
 id int(11) default NULL

mysql-test/t/subselect.test

@@ -543,8 +543,8 @@ drop table t1, t2;
 
 CREATE TABLE `t1` (`i` int(11) NOT NULL default '0',PRIMARY KEY  (`i`)) ENGINE=MyISAM CHARSET=latin1;
 INSERT INTO t1 VALUES (1);
--- error 1111
 UPDATE t1 SET i=i+1 WHERE i=(SELECT MAX(i));
+select * from t1;
 drop table t1;
 
 #test of uncacheable subqueries
@@ -689,12 +689,11 @@ CREATE TABLE `t1` (
 ) ENGINE=MyISAM CHARSET=latin1;
 
 INSERT INTO t1 VALUES (1);
--- error 1111
 UPDATE t1 SET i=i+(SELECT MAX(i) FROM (SELECT 1) t) WHERE i=(SELECT MAX(i));
--- error 1111
 UPDATE t1 SET i=i+1 WHERE i=(SELECT MAX(i));
 -- error 1109
 UPDATE t1 SET t.i=i+(SELECT MAX(i) FROM (SELECT 1) t);
+select * from t1;
 drop table t1;
 
 #

sql/item_subselect.cc

@@ -164,12 +164,7 @@ bool Item_subselect::fix_fields(THD *thd_param, TABLE_LIST *tables, Item **ref)
       thd->where= "checking transformed subquery";
       if (!(*ref)->fixed)
 	ret= (*ref)->fix_fields(thd, tables, ref);
-      // We can't substitute aggregate functions like "SELECT (max(i))"
-      if (substype() == SINGLEROW_SUBS && (*ref)->with_sum_func)
-      {
-	my_error(ER_INVALID_GROUP_FUNC_USE, MYF(0));
-	return 1;
-      }
+      thd->where= save_where;
       return ret;
     }
     // Is it one field subselect?
@@ -322,6 +317,7 @@ Item_singlerow_subselect::select_transformer(JOIN *join)
   if (!select_lex->master_unit()->first_select()->next_select() &&
       !select_lex->table_list.elements &&
       select_lex->item_list.elements == 1 &&
+      !select_lex->item_list.head()->with_sum_func &&
       /*
 	We cant change name of Item_field or Item_ref, because it will
 	prevent it's correct resolving, but we should save name of
@@ -330,7 +326,13 @@ Item_singlerow_subselect::select_transformer(JOIN *join)
 	TODO: solve above problem
       */
       !(select_lex->item_list.head()->type() == FIELD_ITEM ||
-	select_lex->item_list.head()->type() == REF_ITEM)
+	select_lex->item_list.head()->type() == REF_ITEM) &&
+      /*
+        switch off this optimisation for prepare statement,
+        because we do not rollback this changes
+        TODO: make rollback for it, or special name resolving mode in 5.0.
+      */
+      !arena->is_stmt_prepare()
       )
   {
 
@@ -352,9 +354,6 @@ Item_singlerow_subselect::select_transformer(JOIN *join)
     if (join->conds || join->having)
     {
       Item *cond;
-      if (arena->is_stmt_prepare())
-	thd->set_n_backup_item_arena(arena, &backup);
-
       if (!join->having)
 	cond= join->conds;
       else if (!join->conds)
@@ -365,16 +364,12 @@ Item_singlerow_subselect::select_transformer(JOIN *join)
       if (!(substitution= new Item_func_if(cond, substitution,
 					   new Item_null())))
 	goto err;
-      if (arena->is_stmt_prepare())
-        thd->restore_backup_item_arena(arena, &backup);
    }
     return RES_REDUCE;
   }
   return RES_OK;
 
 err:
-  if (arena->is_stmt_prepare())
-    thd->restore_backup_item_arena(arena, &backup);
   return RES_ERROR;
 }
 
@@ -401,6 +396,13 @@ void Item_singlerow_subselect::fix_length_and_dec()
     engine->fix_length_and_dec(row);
     value= *row;
   }
+  /*
+    If there are not tables in subquery then ability to have NULL value
+    depends on SELECT list (if single row subquery have tables then it
+    always can be NULL if there are not records fetched).
+  */
+  if (engine->no_tables())
+    maybe_null= engine->may_be_null();
 }
 
 uint Item_singlerow_subselect::cols()
@@ -644,6 +646,7 @@ Item_subselect::trans_res
 Item_in_subselect::single_value_transformer(JOIN *join,
 					    Comp_creator *func)
 {
+  const char *save_where= thd->where;
   DBUG_ENTER("Item_in_subselect::single_value_transformer");
 
   if (changed)
@@ -899,6 +902,7 @@ Item_in_subselect::single_value_transformer(JOIN *join,
 ok:
   if (arena->is_stmt_prepare())
     thd->restore_backup_item_arena(arena, &backup);
+  thd->where= save_where;
   DBUG_RETURN(RES_OK);
 
 err:
@@ -911,6 +915,7 @@ err:
 Item_subselect::trans_res
 Item_in_subselect::row_value_transformer(JOIN *join)
 {
+  const char *save_where= thd->where;
   DBUG_ENTER("Item_in_subselect::row_value_transformer");
 
   if (changed)
@@ -1003,6 +1008,7 @@ Item_in_subselect::row_value_transformer(JOIN *join)
   }
   if (arena->is_stmt_prepare())
     thd->restore_backup_item_arena(arena, &backup);
+  thd->where= save_where;
   DBUG_RETURN(RES_OK);
 
 err:
@@ -1562,3 +1568,58 @@ int subselect_uniquesubquery_engine::change_item(Item_subselect *si,
   DBUG_ASSERT(0);
   return -1;
 }
+
+
+/*
+  Report about presence of tables in subquery
+
+  SINOPSYS
+    subselect_single_select_engine::no_tables()
+
+  RETURN
+    TRUE  there are not tables used in subquery
+    FALSE there are some tables in subquery
+*/
+bool subselect_single_select_engine::no_tables()
+{
+  return(select_lex->table_list.elements == 0);
+}
+
+
+/*
+  Report about presence of tables in subquery
+
+  SINOPSYS
+    subselect_union_engine::no_tables()
+
+  RETURN
+    TRUE  there are not tables used in subquery
+    FALSE there are some tables in subquery
+*/
+bool subselect_union_engine::no_tables()
+{
+  for (SELECT_LEX *sl= unit->first_select(); sl; sl= sl->next_select())
+  {
+    if (sl->table_list.elements)
+      return FALSE;
+  }
+  return TRUE;
+}
+
+
+/*
+  Report about presence of tables in subquery
+
+  SINOPSYS
+    subselect_uniquesubquery_engine::no_tables()
+
+  RETURN
+    TRUE  there are not tables used in subquery
+    FALSE there are some tables in subquery
+*/
+
+bool subselect_uniquesubquery_engine::no_tables()
+{
+  /* returning value is correct, but this method should never be called */
+  return 0;
+}

sql/item_subselect.h

@@ -291,6 +291,7 @@ public:
   static table_map calc_const_tables(TABLE_LIST *);
   virtual void print(String *str)= 0;
   virtual int change_item(Item_subselect *si, select_subselect *result)= 0;
+  virtual bool no_tables()= 0;
 };
 
 
@@ -315,6 +316,7 @@ public:
   table_map upper_select_const_tables();
   void print (String *str);
   int change_item(Item_subselect *si, select_subselect *result);
+  bool no_tables();
 };
 
 
@@ -335,6 +337,7 @@ public:
   table_map upper_select_const_tables();
   void print (String *str);
   int change_item(Item_subselect *si, select_subselect *result);
+  bool no_tables();
 };
 
 
@@ -364,6 +367,7 @@ public:
   table_map upper_select_const_tables() { return 0; }
   void print (String *str);
   int change_item(Item_subselect *si, select_subselect *result);
+  bool no_tables();
 };