Bug#57039: constant subtime expression returns incorrect result.

The subtime function wasn't able to produce correct int representation of
its result. For constant expressions the Item_datetime_cache is used to
speedup evaluation and Item_datetime_cache expects underlying item to return
correct int representation of DATETIME value. These two factors combined led
to a wrong query result.

Now the Item_func_add_time has function val_datetime which performs the
calculation and saves result into given MYSQL_TIME struct, it also sets
null_value to appropriate value. val_int and val_str member functions
convert the result obtained from val_datetime to int or string respectively
and returns it.

mysql-test/r/func_time.result:
  Added a test case for the bug#57039.
mysql-test/t/func_time.test:
  Added a test case for the bug#57039.
sql/item_timefunc.cc:
  Bug#57039: constant subtime expression returns incorrect result.
  Now the Item_func_add_time has function val_datetime which performs the
  calculation and saves result into given MYSQL_TIME struct, it also sets
  null_value to appropriate value. val_int and val_str member functions
  convert the result obtained from val_datetime to int or string respectively
  and returns it.
sql/item_timefunc.h:
  Bug#57039: constant subtime expression returns incorrect result.

1 files changed, 2 insertions, 0 deletions

diff --git a/sql/item_timefunc.h b/sql/item_timefunc.h
index 6e31b5c6705..d82a8f9e969 100644
--- a/sql/item_timefunc.h
+++ b/sql/item_timefunc.h
@@ -949,6 +949,8 @@ public:
       return save_date_in_field(field);
     return Item_str_func::save_in_field(field, no_conversions);
   }
+  longlong val_int();
+  MYSQL_TIME *val_datetime(MYSQL_TIME *time, date_time_format_types *format);
 };
 
 class Item_func_timediff :public Item_str_timefunc