Fix for bug #7586 "TIMEDIFF for sec+microsec not working properly".

mysql-test/r/func_sapdb.result

@@ -97,13 +97,16 @@ timediff("1997-12-31 23:59:59.000001","1997-12-30 01:01:01.000002")
 46:58:57.999999
 select timediff("1997-12-30 23:59:59.000001","1997-12-31 23:59:59.000002");
 timediff("1997-12-30 23:59:59.000001","1997-12-31 23:59:59.000002")
--23:59:59.999999
+-24:00:00.000001
 select timediff("1997-12-31 23:59:59.000001","23:59:59.000001");
 timediff("1997-12-31 23:59:59.000001","23:59:59.000001")
 NULL
 select timediff("2000:01:01 00:00:00", "2000:01:01 00:00:00.000001");
 timediff("2000:01:01 00:00:00", "2000:01:01 00:00:00.000001")
 -00:00:00.000001
+select timediff("2005-01-11 15:48:49.999999", "2005-01-11 15:48:50");
+timediff("2005-01-11 15:48:49.999999", "2005-01-11 15:48:50")
+-00:00:00.000001
 select maketime(10,11,12);
 maketime(10,11,12)
 10:11:12
@@ -175,7 +178,7 @@ f8	date	YES		NULL
 f9	time	YES		NULL	
 select * from t1;
 f1	f2	f3	f4	f5	f6	f7	f8	f9
-1997-01-01	1998-01-02 01:01:00	49:01:01	46:58:57	-23:59:59	10:11:12	2001-12-01 01:01:01	1997-12-31	23:59:59
+1997-01-01	1998-01-02 01:01:00	49:01:01	46:58:57	-24:00:00	10:11:12	2001-12-01 01:01:01	1997-12-31	23:59:59
 create table test(t1 datetime, t2 time, t3 time, t4 datetime);
 insert into test values 
 ('2001-01-01 01:01:01', '01:01:01', null, '2001-02-01 01:01:01'),

mysql-test/t/func_sapdb.test

@@ -54,6 +54,7 @@ select timediff("1997-12-31 23:59:59.000001","1997-12-30 01:01:01.000002");
 select timediff("1997-12-30 23:59:59.000001","1997-12-31 23:59:59.000002");
 select timediff("1997-12-31 23:59:59.000001","23:59:59.000001");
 select timediff("2000:01:01 00:00:00", "2000:01:01 00:00:00.000001");
+select timediff("2005-01-11 15:48:49.999999", "2005-01-11 15:48:50");
 --enable_ps_protocol
 
 select maketime(10,11,12);

sql/item_timefunc.cc

@@ -2432,8 +2432,7 @@ void Item_func_add_time::print(String *str)
 String *Item_func_timediff::val_str(String *str)
 {
   DBUG_ASSERT(fixed == 1);
-  longlong seconds;
-  long microseconds;
+  longlong microseconds;
   long days;
   int l_sign= 1;
   TIME l_time1 ,l_time2, l_time3;
@@ -2457,32 +2456,23 @@ String *Item_func_timediff::val_str(String *str)
 			     (uint) l_time2.month,
 			     (uint) l_time2.day));
 
-  microseconds= l_time1.second_part - l_sign*l_time2.second_part;
-  seconds= ((longlong) days*86400L + l_time1.hour*3600L + 
-	    l_time1.minute*60L + l_time1.second + microseconds/1000000L -
-	    (longlong)l_sign*(l_time2.hour*3600L+l_time2.minute*60L+
-			      l_time2.second));
+  microseconds= ((longlong)days*86400L +
+                 l_time1.hour*3600L + l_time1.minute*60L + l_time1.second -
+                 (longlong)l_sign*(l_time2.hour*3600L + l_time2.minute*60L +
+                                   l_time2.second))*1000000 +
+                 l_time1.second_part - l_sign*l_time2.second_part;
 
   l_time3.neg= 0;
-  if (seconds < 0)
-  {
-    seconds= -seconds;
-    l_time3.neg= 1;
-  }
-  else if (seconds == 0 && microseconds < 0)
+  if (microseconds < 0)
   {
     microseconds= -microseconds;
     l_time3.neg= 1;
   }
-  if (microseconds < 0)
-  {
-    microseconds+= 1000000L;
-    seconds--;
-  }
-  if ((l_time2.neg == l_time1.neg) && l_time1.neg)
+  if ((l_time2.neg == l_time1.neg) && l_time1.neg && microseconds)
     l_time3.neg= l_time3.neg ? 0 : 1;
 
-  calc_time_from_sec(&l_time3, (long) seconds, microseconds);
+  calc_time_from_sec(&l_time3, (long)(microseconds/1000000),
+                               (long)(microseconds%1000000));
 
   if (!make_datetime(l_time1.second_part || l_time2.second_part ?
 		     TIME_MICROSECOND : TIME_ONLY,