Index: timestamp.c
===================================================================
RCS file: /cvsroot/pgsql/src/backend/utils/adt/timestamp.c,v
retrieving revision 1.179
diff -c -r1.179 timestamp.c
*** timestamp.c	6 Jul 2007 04:15:59 -0000	1.179
--- timestamp.c	8 Jul 2007 19:45:04 -0000
***************
*** 3044,3050 ****
  	if (timestamp2tm(dt1, NULL, tm1, &fsec1, NULL, NULL) == 0 &&
  		timestamp2tm(dt2, NULL, tm2, &fsec2, NULL, NULL) == 0)
  	{
! 		fsec = (fsec1 - fsec2);
  		tm->tm_sec = tm1->tm_sec - tm2->tm_sec;
  		tm->tm_min = tm1->tm_min - tm2->tm_min;
  		tm->tm_hour = tm1->tm_hour - tm2->tm_hour;
--- 3044,3051 ----
  	if (timestamp2tm(dt1, NULL, tm1, &fsec1, NULL, NULL) == 0 &&
  		timestamp2tm(dt2, NULL, tm2, &fsec2, NULL, NULL) == 0)
  	{
! 		/* form the symbolic difference */
! 		fsec = fsec1 - fsec2;
  		tm->tm_sec = tm1->tm_sec - tm2->tm_sec;
  		tm->tm_min = tm1->tm_min - tm2->tm_min;
  		tm->tm_hour = tm1->tm_hour - tm2->tm_hour;
***************
*** 3064,3069 ****
--- 3065,3081 ----
  			tm->tm_year = -tm->tm_year;
  		}
  
+ 		/* propagate any negative fields into the next higher field */
+ 		while (fsec < 0)
+ 		{
+ #ifdef HAVE_INT64_TIMESTAMP
+ 			fsec += USECS_PER_SEC;
+ #else
+ 			fsec += 1.0;
+ #endif
+ 			tm->tm_sec--;
+ 		}
+ 
  		while (tm->tm_sec < 0)
  		{
  			tm->tm_sec += SECS_PER_MINUTE;
***************
*** 3082,3097 ****
  			tm->tm_mday--;
  		}
  
! 		while (tm->tm_mday < 0)
  		{
  			if (dt1 < dt2)
  			{
! 				tm->tm_mday += day_tab[isleap(tm1->tm_year)][tm1->tm_mon - 1];
! 				tm->tm_mon--;
  			}
  			else
  			{
! 				tm->tm_mday += day_tab[isleap(tm2->tm_year)][tm2->tm_mon - 1];
  				tm->tm_mon--;
  			}
  		}
--- 3094,3130 ----
  			tm->tm_mday--;
  		}
  
! 		/*
! 		 * day-to-month conversion is tricky because variable.  For each
! 		 * decrement in tm_mon, we should adjust tm_mday by the length of
! 		 * the next-to-last month(s) of the original time interval.
! 		 * This corresponds to the notion that interval addition will add
! 		 * months first, then days.
! 		 */
! 		if (tm->tm_mday < 0)
  		{
+ 			int		end_year;
+ 			int		end_mon;
+ 
  			if (dt1 < dt2)
  			{
! 				end_year = tm2->tm_year;
! 				end_mon = tm2->tm_mon;
  			}
  			else
  			{
! 				end_year = tm1->tm_year;
! 				end_mon = tm1->tm_mon;
! 			}
! 
! 			while (tm->tm_mday < 0)
! 			{
! 				if (--end_mon <= 0)
! 				{
! 					end_mon = MONTHS_PER_YEAR;
! 					end_year--;
! 				}
! 				tm->tm_mday += day_tab[isleap(end_year)][end_mon - 1];
  				tm->tm_mon--;
  			}
  		}
***************
*** 3158,3163 ****
--- 3191,3197 ----
  	if (timestamp2tm(dt1, &tz1, tm1, &fsec1, &tzn, NULL) == 0 &&
  		timestamp2tm(dt2, &tz2, tm2, &fsec2, &tzn, NULL) == 0)
  	{
+ 		/* form the symbolic difference */
  		fsec = fsec1 - fsec2;
  		tm->tm_sec = tm1->tm_sec - tm2->tm_sec;
  		tm->tm_min = tm1->tm_min - tm2->tm_min;
***************
*** 3178,3183 ****
--- 3212,3228 ----
  			tm->tm_year = -tm->tm_year;
  		}
  
+ 		/* propagate any negative fields into the next higher field */
+ 		while (fsec < 0)
+ 		{
+ #ifdef HAVE_INT64_TIMESTAMP
+ 			fsec += USECS_PER_SEC;
+ #else
+ 			fsec += 1.0;
+ #endif
+ 			tm->tm_sec--;
+ 		}
+ 
  		while (tm->tm_sec < 0)
  		{
  			tm->tm_sec += SECS_PER_MINUTE;
***************
*** 3196,3211 ****
  			tm->tm_mday--;
  		}
  
! 		while (tm->tm_mday < 0)
  		{
  			if (dt1 < dt2)
  			{
! 				tm->tm_mday += day_tab[isleap(tm1->tm_year)][tm1->tm_mon - 1];
! 				tm->tm_mon--;
  			}
  			else
  			{
! 				tm->tm_mday += day_tab[isleap(tm2->tm_year)][tm2->tm_mon - 1];
  				tm->tm_mon--;
  			}
  		}
--- 3241,3277 ----
  			tm->tm_mday--;
  		}
  
! 		/*
! 		 * day-to-month conversion is tricky because variable.  For each
! 		 * decrement in tm_mon, we should adjust tm_mday by the length of
! 		 * the next-to-last month(s) of the original time interval.
! 		 * This corresponds to the notion that interval addition will add
! 		 * months first, then days.
! 		 */
! 		if (tm->tm_mday < 0)
  		{
+ 			int		end_year;
+ 			int		end_mon;
+ 
  			if (dt1 < dt2)
  			{
! 				end_year = tm2->tm_year;
! 				end_mon = tm2->tm_mon;
  			}
  			else
  			{
! 				end_year = tm1->tm_year;
! 				end_mon = tm1->tm_mon;
! 			}
! 
! 			while (tm->tm_mday < 0)
! 			{
! 				if (--end_mon <= 0)
! 				{
! 					end_mon = MONTHS_PER_YEAR;
! 					end_year--;
! 				}
! 				tm->tm_mday += day_tab[isleap(end_year)][end_mon - 1];
  				tm->tm_mon--;
  			}
  		}