Fixed bug#16861: User defined variable can have a wrong value if a tmp table was

used.

The Item::save_in_field() function is called from fill_record() to fill the 
new row with data while execution of the CREATE TABLE ... SELECT statement.
Item::save_in_field() calls val_xxx() methods in order to get values.
val_xxx() methods do not take into account the result field. Due to this
Item_func_set_user_var::val_xxx() methods returns values from the original
table, not from the temporary one.

The save_in_field() member function is added to the Item_func_set_user_var
class. It detects whether the result field should be used and properly updates
the value of the user variable.


sql/item_func.cc:
  Bug#16861: User defined variable can have a wrong value if a tmp table was used.
  Added the save_in_field() member function to the Item_func_set_user_var class.
sql/item_func.h:
  Bug#16861: User defined variable can have a wrong value if a tmp table was used.
  Added the save_in_field() member function to the Item_func_set_user_var class.
mysql-test/r/user_var.result:
  Extended the test case for bug#18681: User defined variable can have a wrong value if
  a tmp table was used.
mysql-test/t/user_var.test:
  Extended the test case for bug#18681: User defined variable can have a wrong value if
  a tmp table was used.

1 files changed, 4 insertions, 1 deletions

diff --git a/mysql-test/t/user_var.test b/mysql-test/t/user_var.test
index 65ca1b2c1b7..70f57fdf283 100644
--- a/mysql-test/t/user_var.test
+++ b/mysql-test/t/user_var.test
@@ -210,7 +210,10 @@ create table t1(f1 int, f2 int);
 insert into t1 values (1,2),(2,3),(3,1);
 select @var:=f2 from t1 group by f1 order by f2 desc limit 1;
 select @var;
-drop table t1;
+create table t2 as select @var:=f2 from t1 group by f1 order by f2 desc limit 1;
+select * from t2;
+select @var;
+drop table t1,t2;
 
 #
 # Bug#19024 - SHOW COUNT(*) WARNINGS not return Errors