Break out xxx2yyy_opt_overflow APIs for more datetime conversions.

Previous commits invented timestamp2timestamptz_opt_overflow,
date2timestamp_opt_overflow, and date2timestamptz_opt_overflow
functions to perform non-error-throwing conversions between
datetime types.  This patch completes the set by adding
timestamp2date_opt_overflow, timestamptz2date_opt_overflow,
and timestamptz2timestamp_opt_overflow.

In addition, adjust timestamp2timestamptz_opt_overflow so that it
doesn't throw error if timestamp2tm fails, but treats that as an
overflow case.  The situation probably can't arise except with an
invalid timestamp value, and I can't think of a way that that would
happen except data corruption.  However, it's pretty silly to have a
function whose entire reason for existence is to not throw errors for
out-of-range inputs nonetheless throw an error for out-of-range input.

The new APIs are not used in this patch, but will be needed in
upcoming btree_gin changes.

Author: Tom Lane <tgl@sss.pgh.pa.us>
Reviewed-by: Arseniy Mukhin <arseniy.mukhin.dev@gmail.com>
Discussion: https://postgr.es/m/262624.1738460652@sss.pgh.pa.us

src/backend/utils/adt/date.c

@@ -1363,10 +1363,35 @@ timestamp_date(PG_FUNCTION_ARGS)
 {
 	Timestamp	timestamp = PG_GETARG_TIMESTAMP(0);
 	DateADT		result;
+
+	result = timestamp2date_opt_overflow(timestamp, NULL);
+	PG_RETURN_DATEADT(result);
+}
+
+/*
+ * Convert timestamp to date.
+ *
+ * On successful conversion, *overflow is set to zero if it's not NULL.
+ *
+ * If the timestamp is finite but out of the valid range for date, then:
+ * if overflow is NULL, we throw an out-of-range error.
+ * if overflow is not NULL, we store +1 or -1 there to indicate the sign
+ * of the overflow, and return the appropriate date infinity.
+ *
+ * Note: given the ranges of the types, overflow is only possible at
+ * the minimum end of the range, but we don't assume that in this code.
+ */
+DateADT
+timestamp2date_opt_overflow(Timestamp timestamp, int *overflow)
+{
+	DateADT		result;
 	struct pg_tm tt,
 			   *tm = &tt;
 	fsec_t		fsec;
 
+	if (overflow)
+		*overflow = 0;
+
 	if (TIMESTAMP_IS_NOBEGIN(timestamp))
 		DATE_NOBEGIN(result);
 	else if (TIMESTAMP_IS_NOEND(timestamp))
@@ -1374,14 +1399,30 @@ timestamp_date(PG_FUNCTION_ARGS)
 	else
 	{
 		if (timestamp2tm(timestamp, NULL, tm, &fsec, NULL, NULL) != 0)
+		{
+			if (overflow)
+			{
+				if (timestamp < 0)
+				{
+					*overflow = -1;
+					DATE_NOBEGIN(result);
+				}
+				else
+				{
+					*overflow = 1;	/* not actually reachable */
+					DATE_NOEND(result);
+				}
+				return result;
+			}
 			ereport(ERROR,
 					(errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
 					 errmsg("timestamp out of range")));
+		}
 
 		result = date2j(tm->tm_year, tm->tm_mon, tm->tm_mday) - POSTGRES_EPOCH_JDATE;
 	}
 
-	PG_RETURN_DATEADT(result);
+	return result;
 }
 
 
@@ -1408,11 +1449,36 @@ timestamptz_date(PG_FUNCTION_ARGS)
 {
 	TimestampTz timestamp = PG_GETARG_TIMESTAMP(0);
 	DateADT		result;
+
+	result = timestamptz2date_opt_overflow(timestamp, NULL);
+	PG_RETURN_DATEADT(result);
+}
+
+/*
+ * Convert timestamptz to date.
+ *
+ * On successful conversion, *overflow is set to zero if it's not NULL.
+ *
+ * If the timestamptz is finite but out of the valid range for date, then:
+ * if overflow is NULL, we throw an out-of-range error.
+ * if overflow is not NULL, we store +1 or -1 there to indicate the sign
+ * of the overflow, and return the appropriate date infinity.
+ *
+ * Note: given the ranges of the types, overflow is only possible at
+ * the minimum end of the range, but we don't assume that in this code.
+ */
+DateADT
+timestamptz2date_opt_overflow(TimestampTz timestamp, int *overflow)
+{
+	DateADT		result;
 	struct pg_tm tt,
 			   *tm = &tt;
 	fsec_t		fsec;
 	int			tz;
 
+	if (overflow)
+		*overflow = 0;
+
 	if (TIMESTAMP_IS_NOBEGIN(timestamp))
 		DATE_NOBEGIN(result);
 	else if (TIMESTAMP_IS_NOEND(timestamp))
@@ -1420,14 +1486,30 @@ timestamptz_date(PG_FUNCTION_ARGS)
 	else
 	{
 		if (timestamp2tm(timestamp, &tz, tm, &fsec, NULL, NULL) != 0)
+		{
+			if (overflow)
+			{
+				if (timestamp < 0)
+				{
+					*overflow = -1;
+					DATE_NOBEGIN(result);
+				}
+				else
+				{
+					*overflow = 1;	/* not actually reachable */
+					DATE_NOEND(result);
+				}
+				return result;
+			}
 			ereport(ERROR,
 					(errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
 					 errmsg("timestamp out of range")));
+		}
 
 		result = date2j(tm->tm_year, tm->tm_mon, tm->tm_mday) - POSTGRES_EPOCH_JDATE;
 	}
 
-	PG_RETURN_DATEADT(result);
+	return result;
 }
 
 

src/backend/utils/adt/timestamp.c

@@ -6477,7 +6477,7 @@ timestamp2timestamptz_opt_overflow(Timestamp timestamp, int *overflow)
 	if (TIMESTAMP_NOT_FINITE(timestamp))
 		return timestamp;
 
-	/* We don't expect this to fail, but check it pro forma */
+	/* timestamp2tm should not fail on valid timestamps, but cope */
 	if (timestamp2tm(timestamp, NULL, tm, &fsec, NULL, NULL) == 0)
 	{
 		tz = DetermineTimeZoneOffset(tm, session_timezone);
@@ -6485,23 +6485,22 @@ timestamp2timestamptz_opt_overflow(Timestamp timestamp, int *overflow)
 		result = dt2local(timestamp, -tz);
 
 		if (IS_VALID_TIMESTAMP(result))
-		{
 			return result;
-		}
+	}
-		else if (overflow)
+
+	if (overflow)
+	{
+		if (timestamp < 0)
 		{
-			if (result < MIN_TIMESTAMP)
+			*overflow = -1;
-			{
+			TIMESTAMP_NOBEGIN(result);
-				*overflow = -1;
-				TIMESTAMP_NOBEGIN(result);
-			}
-			else
-			{
-				*overflow = 1;
-				TIMESTAMP_NOEND(result);
-			}
-			return result;
 		}
+		else
+		{
+			*overflow = 1;
+			TIMESTAMP_NOEND(result);
+		}
+		return result;
 	}
 
 	ereport(ERROR,
@@ -6531,8 +6530,27 @@ timestamptz_timestamp(PG_FUNCTION_ARGS)
 	PG_RETURN_TIMESTAMP(timestamptz2timestamp(timestamp));
 }
 
+/*
+ * Convert timestamptz to timestamp, throwing error for overflow.
+ */
 static Timestamp
 timestamptz2timestamp(TimestampTz timestamp)
+{
+	return timestamptz2timestamp_opt_overflow(timestamp, NULL);
+}
+
+/*
+ * Convert timestamp with time zone to timestamp.
+ *
+ * On successful conversion, *overflow is set to zero if it's not NULL.
+ *
+ * If the timestamptz is finite but out of the valid range for timestamp, then:
+ * if overflow is NULL, we throw an out-of-range error.
+ * if overflow is not NULL, we store +1 or -1 there to indicate the sign
+ * of the overflow, and return the appropriate timestamp infinity.
+ */
+Timestamp
+timestamptz2timestamp_opt_overflow(TimestampTz timestamp, int *overflow)
 {
 	Timestamp	result;
 	struct pg_tm tt,
@@ -6540,18 +6558,53 @@ timestamptz2timestamp(TimestampTz timestamp)
 	fsec_t		fsec;
 	int			tz;
 
+	if (overflow)
+		*overflow = 0;
+
 	if (TIMESTAMP_NOT_FINITE(timestamp))
 		result = timestamp;
 	else
 	{
 		if (timestamp2tm(timestamp, &tz, tm, &fsec, NULL, NULL) != 0)
+		{
+			if (overflow)
+			{
+				if (timestamp < 0)
+				{
+					*overflow = -1;
+					TIMESTAMP_NOBEGIN(result);
+				}
+				else
+				{
+					*overflow = 1;
+					TIMESTAMP_NOEND(result);
+				}
+				return result;
+			}
 			ereport(ERROR,
 					(errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
 					 errmsg("timestamp out of range")));
+		}
 		if (tm2timestamp(tm, fsec, NULL, &result) != 0)
+		{
+			if (overflow)
+			{
+				if (timestamp < 0)
+				{
+					*overflow = -1;
+					TIMESTAMP_NOBEGIN(result);
+				}
+				else
+				{
+					*overflow = 1;
+					TIMESTAMP_NOEND(result);
+				}
+				return result;
+			}
 			ereport(ERROR,
 					(errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
 					 errmsg("timestamp out of range")));
+		}
 	}
 	return result;
 }

src/include/utils/date.h

@@ -100,6 +100,8 @@ extern int32 anytime_typmod_check(bool istz, int32 typmod);
 extern double date2timestamp_no_overflow(DateADT dateVal);
 extern Timestamp date2timestamp_opt_overflow(DateADT dateVal, int *overflow);
 extern TimestampTz date2timestamptz_opt_overflow(DateADT dateVal, int *overflow);
+extern DateADT timestamp2date_opt_overflow(Timestamp timestamp, int *overflow);
+extern DateADT timestamptz2date_opt_overflow(TimestampTz timestamp, int *overflow);
 extern int32 date_cmp_timestamp_internal(DateADT dateVal, Timestamp dt2);
 extern int32 date_cmp_timestamptz_internal(DateADT dateVal, TimestampTz dt2);
 

src/include/utils/timestamp.h

@@ -144,6 +144,9 @@ extern int	timestamp_cmp_internal(Timestamp dt1, Timestamp dt2);
 
 extern TimestampTz timestamp2timestamptz_opt_overflow(Timestamp timestamp,
 													  int *overflow);
+extern Timestamp timestamptz2timestamp_opt_overflow(TimestampTz timestamp,
+													int *overflow);
+
 extern int32 timestamp_cmp_timestamptz_internal(Timestamp timestampVal,
 												TimestampTz dt2);