Fix up timetz input so that a date is required only when the specified

timezone actually has a daylight-savings rule.  This avoids breaking
cases that used to work because they went through the DecodePosixTimezone
code path.  Per contrib regression failures (mea culpa for not running
those yesterday...).  Also document the already-applied change to allow
GMT offsets up to 14 hours.

5 files changed, 72 insertions, 21 deletions

diff --git a/doc/src/sgml/datatype.sgml b/doc/src/sgml/datatype.sgml
index d4c0dba9ab..76739a5aad 100644
--- a/doc/src/sgml/datatype.sgml
+++ b/doc/src/sgml/datatype.sgml
@@ -1356,8 +1356,8 @@ SELECT b, char_length(b) FROM test2;
         <entry><type>time [ (<replaceable>p</replaceable>) ] with time zone</type></entry>
         <entry>12 bytes</entry>
         <entry>times of day only, with time zone</entry>
-        <entry>00:00:00+1359</entry>
-        <entry>24:00:00-1359</entry>
+        <entry>00:00:00+1459</entry>
+        <entry>24:00:00-1459</entry>
         <entry>1 microsecond / 14 digits</entry>
        </row>
       </tbody>
@@ -1594,7 +1594,8 @@ SELECT b, char_length(b) FROM test2;
       and <xref linkend="datatype-timezone-table">.)  If a time zone is
       specified in the input for <type>time without time zone</type>,
       it is silently ignored. You can also specify a date but it will
-      be ignored, except when you use a full time zone name like
+      be ignored, except when you use a time zone name that involves a
+      daylight-savings rule, such as
       <literal>America/New_York</literal>. In this case specifying the date
       is required in order to determine whether standard or daylight-savings
       time applies.  The appropriate time zone offset is recorded in the
@@ -1747,12 +1748,7 @@ SELECT b, char_length(b) FROM test2;
 </programlisting>
 
       are valid values, which follow the <acronym>ISO</acronym> 8601
-      standard. You can also specify the full time zone name as in
-<programlisting>
-1999-01-08 04:05:06 America/New_York
-</programlisting>
-
-      In addition, the wide-spread format
+      standard.  In addition, the wide-spread format
 <programlisting>
 January 8 04:05:06 1999 PST
 </programlisting>
@@ -2210,12 +2206,7 @@ January 8 04:05:06 1999 PST
      There is a conceptual and practical difference between the abbreviations
      and the full names: abbreviations always represent a fixed offset from
      UTC, whereas most of the full names imply a local daylight-savings time
-     rule and so have two possible UTC offsets. That's why you always have to
-     specify a date if you want to use full time zone names in <type>timetz</>
-     values. This is also the reason why you should set <xref
-     linkend="guc-timezone"> to a full time zone name: this way,
-     <productname>PostgreSQL</productname>
-     will always know the correct UTC offset for your region.
+     rule and so have two possible UTC offsets.
     </para>
 
     <para>
diff --git a/src/backend/utils/adt/datetime.c b/src/backend/utils/adt/datetime.c
index c5a5a2bce8..b4a2105904 100644
--- a/src/backend/utils/adt/datetime.c
+++ b/src/backend/utils/adt/datetime.c
@@ -1199,6 +1199,18 @@ DecodeDateTime(char **field, int *ftype, int nf,
 						ptype = val;
 						break;
 
+					case UNKNOWN_FIELD:
+						/*
+						 * Before giving up and declaring error, check to see
+						 * if it is an all-alpha timezone name.
+						 */
+						namedTz = pg_tzset(field[i]);
+						if (!namedTz)
+							return DTERR_BAD_FORMAT;
+						/* we'll apply the zone setting below */
+						tmask = DTK_M(TZ);
+						break;
+
 					default:
 						return DTERR_BAD_FORMAT;
 				}
@@ -1911,6 +1923,18 @@ DecodeTimeOnly(char **field, int *ftype, int nf,
 						ptype = val;
 						break;
 
+					case UNKNOWN_FIELD:
+						/*
+						 * Before giving up and declaring error, check to see
+						 * if it is an all-alpha timezone name.
+						 */
+						namedTz = pg_tzset(field[i]);
+						if (!namedTz)
+							return DTERR_BAD_FORMAT;
+						/* we'll apply the zone setting below */
+						tmask = DTK_M(TZ);
+						break;
+
 					default:
 						return DTERR_BAD_FORMAT;
 				}
@@ -1952,18 +1976,28 @@ DecodeTimeOnly(char **field, int *ftype, int nf,
 
 	/*
 	 * If we had a full timezone spec, compute the offset (we could not
-	 * do it before, because we need the date to resolve DST status).
+	 * do it before, because we may need the date to resolve DST status).
 	 */
 	if (namedTz != NULL)
 	{
-		/* a date has to be specified */
-		if ((fmask & DTK_DATE_M) != DTK_DATE_M)
-			return DTERR_BAD_FORMAT;
+		long int	gmtoff;
+
 		/* daylight savings time modifier disallowed with full TZ */
 		if (fmask & DTK_M(DTZMOD))
 			return DTERR_BAD_FORMAT;
 
-		*tzp = DetermineTimeZoneOffset(tm, namedTz);
+		/* if non-DST zone, we do not need to know the date */
+		if (pg_get_timezone_offset(namedTz, &gmtoff))
+		{
+			*tzp = -(int) gmtoff;
+		}
+		else
+		{
+			/* a date has to be specified */
+			if ((fmask & DTK_DATE_M) != DTK_DATE_M)
+				return DTERR_BAD_FORMAT;
+			*tzp = DetermineTimeZoneOffset(tm, namedTz);
+		}
 	}
 
 	/* timezone not specified? then find local timezone if possible */
diff --git a/src/include/pgtime.h b/src/include/pgtime.h
index 0b80ec78db..ab7ed38cba 100644
--- a/src/include/pgtime.h
+++ b/src/include/pgtime.h
@@ -55,6 +55,7 @@ extern size_t pg_strftime(char *s, size_t max, const char *format,
 extern void pg_timezone_initialize(void);
 extern pg_tz *pg_tzset(const char *tzname);
 extern bool tz_acceptable(pg_tz *tz);
+extern bool pg_get_timezone_offset(const pg_tz *tz, long int *gmtoff);
 extern const char *pg_get_timezone_name(pg_tz *tz);
 
 extern pg_tzenum *pg_tzenumerate_start(void);
diff --git a/src/include/utils/datetime.h b/src/include/utils/datetime.h
index 07d1460896..b1cb7819a3 100644
--- a/src/include/utils/datetime.h
+++ b/src/include/utils/datetime.h
@@ -176,7 +176,7 @@
 #define DTK_DATE_M		(DTK_M(YEAR) | DTK_M(MONTH) | DTK_M(DAY))
 #define DTK_TIME_M		(DTK_M(HOUR) | DTK_M(MINUTE) | DTK_M(SECOND))
 
-#define MAXDATELEN		51		/* maximum possible length of an input date
+#define MAXDATELEN		63		/* maximum possible length of an input date
 								 * string (not counting tr. null) */
 #define MAXDATEFIELDS	25		/* maximum possible number of fields in a date
 								 * string */
diff --git a/src/timezone/localtime.c b/src/timezone/localtime.c
index 1ceb756b7f..954c50d847 100644
--- a/src/timezone/localtime.c
+++ b/src/timezone/localtime.c
@@ -1067,6 +1067,31 @@ pg_next_dst_boundary(const pg_time_t *timep,
 }
 
 /*
+ * If the given timezone uses only one GMT offset, store that offset
+ * into *gmtoff and return TRUE, else return FALSE.
+ */
+bool
+pg_get_timezone_offset(const pg_tz *tz, long int *gmtoff)
+{
+	/*
+	 * The zone could have more than one ttinfo, if it's historically used
+	 * more than one abbreviation.  We return TRUE as long as they all have
+	 * the same gmtoff.
+	 */
+	const struct state *sp;
+	int			i;
+
+	sp = &tz->state;
+	for (i = 1; i < sp->typecnt; i++)
+	{
+		if (sp->ttis[i].tt_gmtoff != sp->ttis[0].tt_gmtoff)
+			return false;
+	}
+	*gmtoff = sp->ttis[0].tt_gmtoff;
+	return true;
+}
+
+/*
  * Return the name of the current timezone
  */
 const char *