Implement TZH and TZM timestamp format patterns

These are compatible with Oracle and required for the datetime template
language for jsonpath in an upcoming patch.

Nikita Glukhov and Andrew Dunstan, reviewed by Pavel Stehule.

src/backend/utils/adt/formatting.c

@@ -424,7 +424,10 @@ typedef struct
 				j,
 				us,
 				yysz,			/* is it YY or YYYY ? */
-				clock;			/* 12 or 24 hour clock? */
+				clock,			/* 12 or 24 hour clock? */
+				tzsign,			/* +1, -1 or 0 if timezone info is absent */
+				tzh,
+				tzm;
 } TmFromChar;
 
 #define ZERO_tmfc(_X) memset(_X, 0, sizeof(TmFromChar))
@@ -470,6 +473,7 @@ do {	\
 	(_X)->tm_sec  = (_X)->tm_year = (_X)->tm_min = (_X)->tm_wday = \
 	(_X)->tm_hour = (_X)->tm_yday = (_X)->tm_isdst = 0; \
 	(_X)->tm_mday = (_X)->tm_mon  = 1; \
+	(_X)->tm_zone = NULL; \
 } while(0)
 
 #define ZERO_tmtc(_X) \
@@ -609,6 +613,8 @@ typedef enum
 	DCH_RM,
 	DCH_SSSS,
 	DCH_SS,
+	DCH_TZH,
+	DCH_TZM,
 	DCH_TZ,
 	DCH_US,
 	DCH_WW,
@@ -756,7 +762,9 @@ static const KeyWord DCH_keywords[] = {
 	{"RM", 2, DCH_RM, false, FROM_CHAR_DATE_GREGORIAN}, /* R */
 	{"SSSS", 4, DCH_SSSS, true, FROM_CHAR_DATE_NONE},	/* S */
 	{"SS", 2, DCH_SS, true, FROM_CHAR_DATE_NONE},
-	{"TZ", 2, DCH_TZ, false, FROM_CHAR_DATE_NONE},	/* T */
+	{"TZH", 3, DCH_TZH, false, FROM_CHAR_DATE_NONE},	/* T */
+	{"TZM", 3, DCH_TZM, true, FROM_CHAR_DATE_NONE},
+	{"TZ", 2, DCH_TZ, false, FROM_CHAR_DATE_NONE},
 	{"US", 2, DCH_US, true, FROM_CHAR_DATE_NONE},	/* U */
 	{"WW", 2, DCH_WW, true, FROM_CHAR_DATE_GREGORIAN},	/* W */
 	{"W", 1, DCH_W, true, FROM_CHAR_DATE_GREGORIAN},
@@ -879,7 +887,7 @@ static const int DCH_index[KeyWord_INDEX_SIZE] = {
 	-1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
 	-1, -1, -1, -1, -1, DCH_A_D, DCH_B_C, DCH_CC, DCH_DAY, -1,
 	DCH_FX, -1, DCH_HH24, DCH_IDDD, DCH_J, -1, -1, DCH_MI, -1, DCH_OF,
-	DCH_P_M, DCH_Q, DCH_RM, DCH_SSSS, DCH_TZ, DCH_US, -1, DCH_WW, -1, DCH_Y_YYY,
+	DCH_P_M, DCH_Q, DCH_RM, DCH_SSSS, DCH_TZH, DCH_US, -1, DCH_WW, -1, DCH_Y_YYY,
 	-1, -1, -1, -1, -1, -1, -1, DCH_a_d, DCH_b_c, DCH_cc,
 	DCH_day, -1, DCH_fx, -1, DCH_hh24, DCH_iddd, DCH_j, -1, -1, DCH_mi,
 	-1, -1, DCH_p_m, DCH_q, DCH_rm, DCH_ssss, DCH_tz, DCH_us, -1, DCH_ww,
@@ -2519,6 +2527,19 @@ DCH_to_char(FormatNode *node, bool is_interval, TmToChar *in, char *out, Oid col
 					s += strlen(s);
 				}
 				break;
+			case DCH_TZH:
+				INVALID_FOR_INTERVAL;
+				sprintf(s, "%c%02d",
+						(tm->tm_gmtoff >= 0) ? '+' : '-',
+						abs((int) tm->tm_gmtoff) / SECS_PER_HOUR);
+				s += strlen(s);
+				break;
+			case DCH_TZM:
+				INVALID_FOR_INTERVAL;
+				sprintf(s, "%02d",
+						(abs((int) tm->tm_gmtoff) % SECS_PER_HOUR) / SECS_PER_MINUTE);
+				s += strlen(s);
+				break;
 			case DCH_OF:
 				INVALID_FOR_INTERVAL;
 				sprintf(s, "%c%0*d",
@@ -3070,6 +3091,20 @@ DCH_from_char(FormatNode *node, char *in, TmFromChar *out)
 						 errmsg("formatting field \"%s\" is only supported in to_char",
 								n->key->name)));
 				break;
+			case DCH_TZH:
+				out->tzsign = *s == '-' ? -1 : +1;
+
+				if (*s == '+' || *s == '-' || *s == ' ')
+					s++;
+
+				from_char_parse_int_len(&out->tzh, &s, 2, n);
+				break;
+			case DCH_TZM:
+				/* assign positive timezone sign if TZH was not seen before */
+				if (!out->tzsign)
+					out->tzsign = +1;
+				from_char_parse_int_len(&out->tzm, &s, 2, n);
+				break;
 			case DCH_A_D:
 			case DCH_B_C:
 			case DCH_a_d:
@@ -3536,7 +3571,16 @@ to_timestamp(PG_FUNCTION_ARGS)
 
 	do_to_timestamp(date_txt, fmt, &tm, &fsec);
 
-	tz = DetermineTimeZoneOffset(&tm, session_timezone);
+	/* Use the specified time zone, if any. */
+	if (tm.tm_zone)
+	{
+		int			dterr = DecodeTimezone((char *) tm.tm_zone, &tz);
+
+		if (dterr)
+			DateTimeParseError(dterr, text_to_cstring(date_txt), "timestamptz");
+	}
+	else
+		tz = DetermineTimeZoneOffset(&tm, session_timezone);
 
 	if (tm2timestamp(&tm, fsec, &tz, &result) != 0)
 		ereport(ERROR,
@@ -3858,6 +3902,23 @@ do_to_timestamp(text *date_txt, text *fmt,
 		*fsec < INT64CONST(0) || *fsec >= USECS_PER_SEC)
 		DateTimeParseError(DTERR_FIELD_OVERFLOW, date_str, "timestamp");
 
+	/* Save parsed time-zone into tm->tm_zone if it was specified */
+	if (tmfc.tzsign)
+	{
+		char	   *tz;
+
+		if (tmfc.tzh < 0 || tmfc.tzh > MAX_TZDISP_HOUR ||
+			tmfc.tzm < 0 || tmfc.tzm >= MINS_PER_HOUR)
+			DateTimeParseError(DTERR_TZDISP_OVERFLOW, date_str, "timestamp");
+
+		tz = palloc(7);
+
+		snprintf(tz, 7, "%c%02d:%02d",
+				 tmfc.tzsign > 0 ? '+' : '-', tmfc.tzh, tmfc.tzm);
+
+		tm->tm_zone = tz;
+	}
+
 	DEBUG_TM(tm);
 
 	pfree(date_str);