1 files changed, 55 insertions, 18 deletions

diff --git a/sql/item_timefunc.cc b/sql/item_timefunc.cc
index a5372a4ae60..9799c5814c4 100644
--- a/sql/item_timefunc.cc
+++ b/sql/item_timefunc.cc
@@ -526,8 +526,11 @@ bool make_date_time(DATE_TIME_FORMAT *format, TIME *l_time,
 	uint year;
 	if (type == TIMESTAMP_TIME)
 	  return 1;
-	length= int10_to_str(calc_week(l_time, 0, (*ptr) == 'U', &year),
-		     intbuff, 10) - intbuff;
+	length= int10_to_str(calc_week(l_time,
+				       (*ptr) == 'U' ?
+				       WEEK_FIRST_WEEKDAY : WEEK_MONDAY_FIRST,
+				       &year),
+			     intbuff, 10) - intbuff;
 	str->append_with_prefill(intbuff, length, 2, '0');
       }
       break;
@@ -537,8 +540,12 @@ bool make_date_time(DATE_TIME_FORMAT *format, TIME *l_time,
 	uint year;
 	if (type == TIMESTAMP_TIME)
 	  return 1;
-	length= int10_to_str(calc_week(l_time, 1, (*ptr) == 'V', &year),
-		     intbuff, 10) - intbuff;
+	length= int10_to_str(calc_week(l_time,
+				       ((*ptr) == 'V' ?
+					(WEEK_YEAR | WEEK_FIRST_WEEKDAY) :
+					(WEEK_YEAR | WEEK_MONDAY_FIRST)),
+				       &year),
+			     intbuff, 10) - intbuff;
 	str->append_with_prefill(intbuff, length, 2, '0');
       }
       break;
@@ -548,7 +555,11 @@ bool make_date_time(DATE_TIME_FORMAT *format, TIME *l_time,
 	uint year;
 	if (type == TIMESTAMP_TIME)
 	  return 1;
-	(void) calc_week(l_time, 1, (*ptr) == 'X', &year);
+	(void) calc_week(l_time,
+			 ((*ptr) == 'X' ?
+			  WEEK_YEAR | WEEK_FIRST_WEEKDAY :
+			  WEEK_YEAR | WEEK_MONDAY_FIRST),
+			 &year);
 	length= int10_to_str(year, intbuff, 10) - intbuff;
 	str->append_with_prefill(intbuff, length, 4, '0');
       }
@@ -718,27 +729,51 @@ longlong Item_func_second::val_int()
 }
 
 
-/*
-  Returns the week of year.
+uint week_mode(uint mode)
+{
+  uint week_format= (mode & 7);
+  if (!(week_format & WEEK_MONDAY_FIRST))
+    week_format^= WEEK_FIRST_WEEKDAY;
+  return week_format;
+}
 
-  The bits in week_format has the following meaning:
-    0	If not set:	USA format: Sunday is first day of week
-        If set:		ISO format: Monday is first day of week
-    1   If not set:	Week is in range 0-53
-    	If set		Week is in range 1-53.
+/*
+  The bits in week_format(for calc_week() function) has the following meaning:
+   WEEK_MONDAY_FIRST (0)  If not set	Sunday is first day of week
+      		   	  If set	Monday is first day of week
+   WEEK_YEAR (1)	  If not set	Week is in range 0-53
+
+   	Week 0 is returned for the the last week of the previous year (for
+	a date at start of january) In this case one can get 53 for the
+	first week of next year.  This flag ensures that the week is
+	relevant for the given year. Note that this flag is only
+	releveant if WEEK_JANUARY is not set.
+
+			  If set	 Week is in range 1-53.
+
+	In this case one may get week 53 for a date in January (when
+	the week is that last week of previous year) and week 1 for a
+	date in December.
+
+  WEEK_FIRST_WEEKDAY (2)  If not set	Weeks are numbered according
+			   		to ISO 8601:1988
+			  If set	The week that contains the first
+					'first-day-of-week' is week 1.
+	
+	ISO 8601:1988 means that if the week containing January 1 has
+	four or more days in the new year, then it is week 1;
+	Otherwise it is the last week of the previous year, and the
+	next week is week 1.
 */
 
 longlong Item_func_week::val_int()
 {
   uint year;
-  uint week_format;
   TIME ltime;
   if (get_arg0_date(&ltime,0))
     return 0;
-  week_format= (uint) args[1]->val_int();
-  return (longlong) calc_week(&ltime, 
-			      (week_format & 2) != 0,
-			      (week_format & 1) == 0,
+  return (longlong) calc_week(&ltime,
+			      week_mode((uint) args[1]->val_int()),
 			      &year);
 }
 
@@ -749,7 +784,9 @@ longlong Item_func_yearweek::val_int()
   TIME ltime;
   if (get_arg0_date(&ltime,0))
     return 0;
-  week=calc_week(&ltime, 1, (args[1]->val_int() & 1) == 0, &year);
+  week= calc_week(&ltime, 
+		  (week_mode((uint) args[1]->val_int()) | WEEK_YEAR),
+		  &year);
   return week+year*100;
 }