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

@@ -1316,3 +1316,14 @@ SELECT 1 FROM t1 ORDER BY @x:=makedate(a,a);
 1
 DROP TABLE t1;
 End of 5.1 tests
+#
+# Bug#57039: constant subtime expression returns incorrect result.
+#
+CREATE TABLE t1 (`date_date` datetime NOT NULL);
+INSERT INTO t1 VALUES ('2008-01-03 00:00:00'), ('2008-01-03 00:00:00');
+SELECT * FROM t1 WHERE date_date >= subtime(now(), "00:30:00");
+date_date
+SELECT * FROM t1 WHERE date_date <= addtime(date_add("2000-1-1", INTERVAL "1:1:1" HOUR_SECOND), "00:20:00");
+date_date
+DROP TABLE t1;
+#

mysql-test/t/func_time.test

@@ -833,3 +833,14 @@ SELECT 1 FROM t1 ORDER BY @x:=makedate(a,a);
 DROP TABLE t1;
 
 --echo End of 5.1 tests
+
+--echo #
+--echo # Bug#57039: constant subtime expression returns incorrect result.
+--echo #
+CREATE TABLE t1 (`date_date` datetime NOT NULL);
+INSERT INTO t1 VALUES ('2008-01-03 00:00:00'), ('2008-01-03 00:00:00');
+SELECT * FROM t1 WHERE date_date >= subtime(now(), "00:30:00");
+SELECT * FROM t1 WHERE date_date <= addtime(date_add("2000-1-1", INTERVAL "1:1:1" HOUR_SECOND), "00:20:00");
+DROP TABLE t1;
+--echo #
+

sql/item_timefunc.cc

@@ -2857,10 +2857,11 @@ void Item_func_add_time::fix_length_and_dec()
   Result: Time value or datetime value
 */
 
-String *Item_func_add_time::val_str(String *str)
+MYSQL_TIME *Item_func_add_time::val_datetime(MYSQL_TIME *time,
+                                             date_time_format_types *format)
 {
   DBUG_ASSERT(fixed == 1);
-  MYSQL_TIME l_time1, l_time2, l_time3;
+  MYSQL_TIME l_time1, l_time2;
   bool is_time= 0;
   long days, microseconds;
   longlong seconds;
@@ -2886,41 +2887,38 @@ String *Item_func_add_time::val_str(String *str)
   if (l_time1.neg != l_time2.neg)
     l_sign= -l_sign;
   
-  bzero((char *)&l_time3, sizeof(l_time3));
+  bzero((char *)time, sizeof(MYSQL_TIME));
   
-  l_time3.neg= calc_time_diff(&l_time1, &l_time2, -l_sign,
-			      &seconds, &microseconds);
+  time->neg= calc_time_diff(&l_time1, &l_time2, -l_sign,
+                            &seconds, &microseconds);
 
   /*
     If first argument was negative and diff between arguments
     is non-zero we need to swap sign to get proper result.
   */
   if (l_time1.neg && (seconds || microseconds))
-    l_time3.neg= 1-l_time3.neg;         // Swap sign of result
+    time->neg= 1 - time->neg;         // Swap sign of result
 
-  if (!is_time && l_time3.neg)
+  if (!is_time && time->neg)
     goto null_date;
 
   days= (long)(seconds/86400L);
 
-  calc_time_from_sec(&l_time3, (long)(seconds%86400L), microseconds);
+  calc_time_from_sec(time, (long)(seconds%86400L), microseconds);
 
   if (!is_time)
   {
-    get_date_from_daynr(days,&l_time3.year,&l_time3.month,&l_time3.day);
-    if (l_time3.day &&
-	!make_datetime(l_time1.second_part || l_time2.second_part ?
-		       DATE_TIME_MICROSECOND : DATE_TIME,
-		       &l_time3, str))
-      return str;
+    get_date_from_daynr(days, &time->year, &time->month, &time->day);
+    *format= l_time1.second_part || l_time2.second_part ?
+             DATE_TIME_MICROSECOND : DATE_TIME;
+    if (time->day)
+      return time;
     goto null_date;
   }
-  
-  l_time3.hour+= days*24;
-  if (!make_datetime_with_warn(l_time1.second_part || l_time2.second_part ?
-                               TIME_MICROSECOND : TIME_ONLY,
-                               &l_time3, str))
-    return str;
+  *format= l_time1.second_part || l_time2.second_part ?
+           TIME_MICROSECOND : TIME_ONLY;
+  time->hour+= days*24;
+  return time;
 
 null_date:
   null_value=1;
@@ -2928,6 +2926,38 @@ null_date:
 }
 
 
+String *Item_func_add_time::val_str(String *str)
+{
+  MYSQL_TIME ltime;
+  date_time_format_types format;
+
+  val_datetime(&ltime, &format);
+
+  if (null_value)
+    return 0;
+
+  if (!make_datetime_with_warn(format, &ltime, str))
+    return str;
+
+  null_value= 1;
+  return 0;
+}
+
+
+longlong Item_func_add_time::val_int()
+{
+  MYSQL_TIME ltime;
+  date_time_format_types format;
+
+  val_datetime(&ltime, &format);
+
+  if (null_value)
+    return 0;
+
+  return TIME_to_ulonglong_datetime(&ltime);
+}
+
+
 void Item_func_add_time::print(String *str, enum_query_type query_type)
 {
   if (is_date)

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