Fix AT TIME ZONE for timestamps without time zones:

	test=> select (CURRENT_DATE + '05:00'::time)::timestamp at time zone
	'Canada/Pacific';
	        timezone
	------------------------
	 2005-07-22 08:00:00-04
	(1 row)

diff --git a/src/backend/utils/adt/timestamp.c b/src/backend/utils/adt/timestamp.c
index 2d9b5ad..999f8fb 100644 (file)
--- a/src/backend/utils/adt/timestamp.c
+++ b/src/backend/utils/adt/timestamp.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *       $PostgreSQL: pgsql/src/backend/utils/adt/timestamp.c,v 1.142 2005/07/22 21:16:15 momjian Exp $
+ *       $PostgreSQL: pgsql/src/backend/utils/adt/timestamp.c,v 1.143 2005/07/23 02:02:27 momjian Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -3922,10 +3922,14 @@ interval_part(PG_FUNCTION_ARGS)
 }
 
 
-/* timestamp_zone()
- * Encode timestamp type with specified time zone.
- * Returns timestamp with time zone, with the input
+/*     timestamp_zone()
+ *     Encode timestamp type with specified time zone.
+ *     Returns timestamp with time zone, with the input
  *     rotated from local time to the specified zone.
+ *     This function is tricky because instead of shifting
+ *     the time _to_ a new time zone, it sets the time to _be_
+ *     the specified timezone.  This requires trickery
+ *     of double-subtracting the requested timezone offset.
  */
 Datum
 timestamp_zone(PG_FUNCTION_ARGS)
@@ -3960,7 +3964,7 @@ timestamp_zone(PG_FUNCTION_ARGS)
 
        /* Apply the timezone change */
        if (timestamp2tm(timestamp, &tz, &tm, &fsec, NULL, tzp) != 0 ||
-           tm2timestamp(&tm, fsec, NULL, &result) != 0)
+           tm2timestamp(&tm, fsec, &tz, &result) != 0)
        {
                ereport(ERROR,
                                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
@@ -3968,6 +3972,9 @@ timestamp_zone(PG_FUNCTION_ARGS)
                                        tzname)));
                PG_RETURN_NULL();
        }
+       /* Must double-adjust for timezone */
+       result = dt2local(result, -tz);
+
        PG_RETURN_TIMESTAMPTZ(result);
 }