fixed updateability VIEW detection (Bug#5146)

fixed other Item_ref methods where result_field involved

mysql-test/r/view.result

@@ -1132,5 +1132,22 @@ select distinct a from t1 limit 2;
 a
 1
 2
+prepare stmt1 from "select distinct a from v1 limit 2";
+execute stmt1;
+a
+1
+2
+execute stmt1;
+a
+1
+2
+deallocate prepare stmt1;
+drop view v1;
+drop table t1;
+create table t1 (tg_column bigint);
+create view v1 as select count(tg_column) as vg_column from t1;
+select avg(vg_column) from v1;
+avg(vg_column)
+0.0000
 drop view v1;
 drop table t1;

mysql-test/t/view.test

@@ -1076,5 +1076,18 @@ create view v1 as select a from t1;
 select distinct a from v1;
 select distinct a from v1 limit 2;
 select distinct a from t1 limit 2;
+prepare stmt1 from "select distinct a from v1 limit 2";
+execute stmt1;
+execute stmt1;
+deallocate prepare stmt1;
+drop view v1;
+drop table t1;
+
+#
+# aggregate function of aggregate function
+#
+create table t1 (tg_column bigint);
+create view v1 as select count(tg_column) as vg_column from t1;
+select avg(vg_column) from v1;
 drop view v1;
 drop table t1;

sql/item.cc

@@ -2141,6 +2141,7 @@ void Item_ref::cleanup()
 {
   DBUG_ENTER("Item_ref::cleanup");
   Item_ident::cleanup();
+  result_field= 0;
   if (hook_ptr)
     *hook_ptr= orig_item;
   DBUG_VOID_RETURN;
@@ -2164,6 +2165,43 @@ bool Item_ref::send(Protocol *prot, String *tmp)
 }
 
 
+double Item_ref::val_result()
+{
+  if (result_field)
+  {
+    if ((null_value= result_field->is_null()))
+      return 0.0;
+    return result_field->val_real();
+  }
+  return val();
+}
+
+
+longlong Item_ref::val_int_result()
+{
+  if (result_field)
+  {
+    if ((null_value= result_field->is_null()))
+      return 0.0;
+    return result_field->val_int();
+  }
+  return val_int();
+}
+
+
+String *Item_ref::str_result(String* str)
+{
+  if (result_field)
+  {
+    if ((null_value= result_field->is_null()))
+      return 0;
+    str->set_charset(str_value.charset());
+    return result_field->val_str(str, &str_value);
+  }
+  return val_str(str);
+}
+
+
 void Item_ref_null_helper::print(String *str)
 {
   str->append("<ref_null_helper>(", 18);

sql/item.h

@@ -964,6 +964,9 @@ class Item_ref :public Item_ident
   {
     return (null_value=(*ref)->get_date_result(ltime,fuzzydate));
   }
+  double val_result();
+  longlong val_int_result();
+  String *str_result(String* tmp);
   bool send(Protocol *prot, String *tmp);
   void make_field(Send_field *field)	{ (*ref)->make_field(field); }
   bool fix_fields(THD *, struct st_table_list *, Item **);

sql/sql_lex.cc

@@ -1540,6 +1540,7 @@ bool st_lex::can_be_merged()
 	  select_lex.order_list.elements == 0 &&
 	  select_lex.group_list.elements == 0 &&
 	  select_lex.having == 0 &&
+          select_lex.with_sum_func == 0 &&
 	  select_lex.table_list.elements == 1 &&
 	  !(select_lex.options & SELECT_DISTINCT) &&
           select_lex.select_limit == HA_POS_ERROR);