Change return type of EXTRACT to numeric

The previous implementation of EXTRACT mapped internally to
date_part(), which returned type double precision (since it was
implemented long before the numeric type existed).  This can lead to
imprecise output in some cases, so returning numeric would be
preferrable.  Changing the return type of an existing function is a
bit risky, so instead we do the following:  We implement a new set of
functions, which are now called "extract", in parallel to the existing
date_part functions.  They work the same way internally but use
numeric instead of float8.  The EXTRACT construct is now mapped by the
parser to these new extract functions.  That way, dumps of views
etc. from old versions (which would use date_part) continue to work
unchanged, but new uses will map to the new extract functions.

Additionally, the reverse compilation of EXTRACT now reproduces the
original syntax, using the new mechanism introduced in
40c24bfef92530bd846e111c1742c2a54441c62c.

The following minor changes of behavior result from the new
implementation:

- The column name from an isolated EXTRACT call is now "extract"
  instead of "date_part".

- Extract from date now rejects inappropriate field names such as
  HOUR.  It was previously mapped internally to extract from
  timestamp, so it would silently accept everything appropriate for
  timestamp.

- Return values when extracting fields with possibly fractional
  values, such as second and epoch, now have the full scale that the
  value has internally (so, for example, '1.000000' instead of just
  '1').

Reported-by: Petr Fedorov <petr.fedorov@phystech.edu>
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://www.postgresql.org/message-id/flat/42b73d2d-da12-ba9f-570a-420e0cce19d9@phystech.edu

1 files changed, 347 insertions, 124 deletions

diff --git a/src/backend/utils/adt/timestamp.c b/src/backend/utils/adt/timestamp.c
index 194861f19e3..b2bdbcab576 100644
--- a/src/backend/utils/adt/timestamp.c
+++ b/src/backend/utils/adt/timestamp.c
@@ -22,6 +22,7 @@
 
 #include "access/xact.h"
 #include "catalog/pg_type.h"
+#include "common/int.h"
 #include "common/int128.h"
 #include "funcapi.h"
 #include "libpq/pqformat.h"
@@ -35,6 +36,7 @@
 #include "utils/date.h"
 #include "utils/datetime.h"
 #include "utils/float.h"
+#include "utils/numeric.h"
 
 /*
  * gcc's -ffast-math switch breaks routines that expect exact results from
@@ -3991,8 +3993,8 @@ timestamptz_bin(PG_FUNCTION_ARGS)
 {
 	Interval   *stride = PG_GETARG_INTERVAL_P(0);
 	TimestampTz timestamp = PG_GETARG_TIMESTAMPTZ(1);
-	TimestampTz	origin = PG_GETARG_TIMESTAMPTZ(2);
-	TimestampTz	result,
+	TimestampTz origin = PG_GETARG_TIMESTAMPTZ(2);
+	TimestampTz result,
 				stride_usecs,
 				tm_diff,
 				tm_delta;
@@ -4597,15 +4599,15 @@ NonFiniteTimestampTzPart(int type, int unit, char *lowunits,
 	}
 }
 
-/* timestamp_part()
+/* timestamp_part() and extract_timestamp()
  * Extract specified field from timestamp.
  */
-Datum
-timestamp_part(PG_FUNCTION_ARGS)
+static Datum
+timestamp_part_common(PG_FUNCTION_ARGS, bool retnumeric)
 {
 	text	   *units = PG_GETARG_TEXT_PP(0);
 	Timestamp	timestamp = PG_GETARG_TIMESTAMP(1);
-	float8		result;
+	int64		intresult;
 	Timestamp	epoch;
 	int			type,
 				val;
@@ -4624,11 +4626,28 @@ timestamp_part(PG_FUNCTION_ARGS)
 
 	if (TIMESTAMP_NOT_FINITE(timestamp))
 	{
-		result = NonFiniteTimestampTzPart(type, val, lowunits,
-										  TIMESTAMP_IS_NOBEGIN(timestamp),
-										  false);
-		if (result)
-			PG_RETURN_FLOAT8(result);
+		double		r = NonFiniteTimestampTzPart(type, val, lowunits,
+												 TIMESTAMP_IS_NOBEGIN(timestamp),
+												 false);
+
+		if (r)
+		{
+			if (retnumeric)
+			{
+				if (r < 0)
+					return DirectFunctionCall3(numeric_in,
+											   CStringGetDatum("-Infinity"),
+											   ObjectIdGetDatum(InvalidOid),
+											   Int32GetDatum(-1));
+				else if (r > 0)
+					return DirectFunctionCall3(numeric_in,
+											   CStringGetDatum("Infinity"),
+											   ObjectIdGetDatum(InvalidOid),
+											   Int32GetDatum(-1));
+			}
+			else
+				PG_RETURN_FLOAT8(r);
+		}
 		else
 			PG_RETURN_NULL();
 	}
@@ -4643,47 +4662,61 @@ timestamp_part(PG_FUNCTION_ARGS)
 		switch (val)
 		{
 			case DTK_MICROSEC:
-				result = tm->tm_sec * 1000000.0 + fsec;
+				intresult = tm->tm_sec * 1000000.0 + fsec;
 				break;
 
 			case DTK_MILLISEC:
-				result = tm->tm_sec * 1000.0 + fsec / 1000.0;
+				if (retnumeric)
+					/*---
+					 * tm->tm_sec * 1000 + fsec / 1000
+					 * = (tm->tm_sec * 1'000'000 + fsec) / 1000
+					 */
+					PG_RETURN_NUMERIC(int64_div_fast_to_numeric(tm->tm_sec * 1000000LL + fsec, 3));
+				else
+					PG_RETURN_FLOAT8(tm->tm_sec * 1000.0 + fsec / 1000.0);
 				break;
 
 			case DTK_SECOND:
-				result = tm->tm_sec + fsec / 1000000.0;
+				if (retnumeric)
+					/*---
+					 * tm->tm_sec + fsec / 1'000'000
+					 * = (tm->tm_sec * 1'000'000 + fsec) / 1'000'000
+					 */
+					PG_RETURN_NUMERIC(int64_div_fast_to_numeric(tm->tm_sec * 1000000LL + fsec, 6));
+				else
+					PG_RETURN_FLOAT8(tm->tm_sec + fsec / 1000000.0);
 				break;
 
 			case DTK_MINUTE:
-				result = tm->tm_min;
+				intresult = tm->tm_min;
 				break;
 
 			case DTK_HOUR:
-				result = tm->tm_hour;
+				intresult = tm->tm_hour;
 				break;
 
 			case DTK_DAY:
-				result = tm->tm_mday;
+				intresult = tm->tm_mday;
 				break;
 
 			case DTK_MONTH:
-				result = tm->tm_mon;
+				intresult = tm->tm_mon;
 				break;
 
 			case DTK_QUARTER:
-				result = (tm->tm_mon - 1) / 3 + 1;
+				intresult = (tm->tm_mon - 1) / 3 + 1;
 				break;
 
 			case DTK_WEEK:
-				result = (float8) date2isoweek(tm->tm_year, tm->tm_mon, tm->tm_mday);
+				intresult = date2isoweek(tm->tm_year, tm->tm_mon, tm->tm_mday);
 				break;
 
 			case DTK_YEAR:
 				if (tm->tm_year > 0)
-					result = tm->tm_year;
+					intresult = tm->tm_year;
 				else
 					/* there is no year 0, just 1 BC and 1 AD */
-					result = tm->tm_year - 1;
+					intresult = tm->tm_year - 1;
 				break;
 
 			case DTK_DECADE:
@@ -4694,9 +4727,9 @@ timestamp_part(PG_FUNCTION_ARGS)
 				 * is 11 BC thru 2 BC...
 				 */
 				if (tm->tm_year >= 0)
-					result = tm->tm_year / 10;
+					intresult = tm->tm_year / 10;
 				else
-					result = -((8 - (tm->tm_year - 1)) / 10);
+					intresult = -((8 - (tm->tm_year - 1)) / 10);
 				break;
 
 			case DTK_CENTURY:
@@ -4708,43 +4741,50 @@ timestamp_part(PG_FUNCTION_ARGS)
 				 * ----
 				 */
 				if (tm->tm_year > 0)
-					result = (tm->tm_year + 99) / 100;
+					intresult = (tm->tm_year + 99) / 100;
 				else
 					/* caution: C division may have negative remainder */
-					result = -((99 - (tm->tm_year - 1)) / 100);
+					intresult = -((99 - (tm->tm_year - 1)) / 100);
 				break;
 
 			case DTK_MILLENNIUM:
 				/* see comments above. */
 				if (tm->tm_year > 0)
-					result = (tm->tm_year + 999) / 1000;
+					intresult = (tm->tm_year + 999) / 1000;
 				else
-					result = -((999 - (tm->tm_year - 1)) / 1000);
+					intresult = -((999 - (tm->tm_year - 1)) / 1000);
 				break;
 
 			case DTK_JULIAN:
-				result = date2j(tm->tm_year, tm->tm_mon, tm->tm_mday);
-				result += ((((tm->tm_hour * MINS_PER_HOUR) + tm->tm_min) * SECS_PER_MINUTE) +
-						   tm->tm_sec + (fsec / 1000000.0)) / (double) SECS_PER_DAY;
+				if (retnumeric)
+					PG_RETURN_NUMERIC(numeric_add_opt_error(int64_to_numeric(date2j(tm->tm_year, tm->tm_mon, tm->tm_mday)),
+															numeric_div_opt_error(int64_to_numeric(((((tm->tm_hour * MINS_PER_HOUR) + tm->tm_min) * SECS_PER_MINUTE) + tm->tm_sec) * 1000000LL + fsec),
+																				  int64_to_numeric(SECS_PER_DAY * 1000000LL),
+																				  NULL),
+															NULL));
+				else
+					PG_RETURN_FLOAT8(date2j(tm->tm_year, tm->tm_mon, tm->tm_mday) +
+									 ((((tm->tm_hour * MINS_PER_HOUR) + tm->tm_min) * SECS_PER_MINUTE) +
+									  tm->tm_sec + (fsec / 1000000.0)) / (double) SECS_PER_DAY);
 				break;
 
 			case DTK_ISOYEAR:
-				result = date2isoyear(tm->tm_year, tm->tm_mon, tm->tm_mday);
+				intresult = date2isoyear(tm->tm_year, tm->tm_mon, tm->tm_mday);
 				/* Adjust BC years */
-				if (result <= 0)
-					result -= 1;
+				if (intresult <= 0)
+					intresult -= 1;
 				break;
 
 			case DTK_DOW:
 			case DTK_ISODOW:
-				result = j2day(date2j(tm->tm_year, tm->tm_mon, tm->tm_mday));
-				if (val == DTK_ISODOW && result == 0)
-					result = 7;
+				intresult = j2day(date2j(tm->tm_year, tm->tm_mon, tm->tm_mday));
+				if (val == DTK_ISODOW && intresult == 0)
+					intresult = 7;
 				break;
 
 			case DTK_DOY:
-				result = (date2j(tm->tm_year, tm->tm_mon, tm->tm_mday)
-						  - date2j(tm->tm_year, 1, 1) + 1);
+				intresult = (date2j(tm->tm_year, tm->tm_mon, tm->tm_mday)
+							 - date2j(tm->tm_year, 1, 1) + 1);
 				break;
 
 			case DTK_TZ:
@@ -4755,7 +4795,7 @@ timestamp_part(PG_FUNCTION_ARGS)
 						(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
 						 errmsg("timestamp units \"%s\" not supported",
 								lowunits)));
-				result = 0;
+				intresult = 0;
 		}
 	}
 	else if (type == RESERV)
@@ -4764,11 +4804,37 @@ timestamp_part(PG_FUNCTION_ARGS)
 		{
 			case DTK_EPOCH:
 				epoch = SetEpochTimestamp();
-				/* try to avoid precision loss in subtraction */
-				if (timestamp < (PG_INT64_MAX + epoch))
-					result = (timestamp - epoch) / 1000000.0;
+				/* (timestamp - epoch) / 1000000 */
+				if (retnumeric)
+				{
+					Numeric		result;
+
+					if (timestamp < (PG_INT64_MAX + epoch))
+						result = int64_div_fast_to_numeric(timestamp - epoch, 6);
+					else
+					{
+						result = numeric_div_opt_error(numeric_sub_opt_error(int64_to_numeric(timestamp),
+																			 int64_to_numeric(epoch),
+																			 NULL),
+													   int64_to_numeric(1000000),
+													   NULL);
+						result = DatumGetNumeric(DirectFunctionCall2(numeric_round,
+																	 NumericGetDatum(result),
+																	 Int32GetDatum(6)));
+					}
+					PG_RETURN_NUMERIC(result);
+				}
 				else
-					result = ((float8) timestamp - epoch) / 1000000.0;
+				{
+					float8		result;
+
+					/* try to avoid precision loss in subtraction */
+					if (timestamp < (PG_INT64_MAX + epoch))
+						result = (timestamp - epoch) / 1000000.0;
+					else
+						result = ((float8) timestamp - epoch) / 1000000.0;
+					PG_RETURN_FLOAT8(result);
+				}
 				break;
 
 			default:
@@ -4776,7 +4842,7 @@ timestamp_part(PG_FUNCTION_ARGS)
 						(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
 						 errmsg("timestamp units \"%s\" not supported",
 								lowunits)));
-				result = 0;
+				intresult = 0;
 		}
 
 	}
@@ -4785,27 +4851,41 @@ timestamp_part(PG_FUNCTION_ARGS)
 		ereport(ERROR,
 				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
 				 errmsg("timestamp units \"%s\" not recognized", lowunits)));
-		result = 0;
+		intresult = 0;
 	}
 
-	PG_RETURN_FLOAT8(result);
+	if (retnumeric)
+		PG_RETURN_NUMERIC(int64_to_numeric(intresult));
+	else
+		PG_RETURN_FLOAT8(intresult);
+}
+
+Datum
+timestamp_part(PG_FUNCTION_ARGS)
+{
+	return timestamp_part_common(fcinfo, false);
 }
 
-/* timestamptz_part()
+Datum
+extract_timestamp(PG_FUNCTION_ARGS)
+{
+	return timestamp_part_common(fcinfo, true);
+}
+
+/* timestamptz_part() and extract_timestamptz()
  * Extract specified field from timestamp with time zone.
  */
-Datum
-timestamptz_part(PG_FUNCTION_ARGS)
+static Datum
+timestamptz_part_common(PG_FUNCTION_ARGS, bool retnumeric)
 {
 	text	   *units = PG_GETARG_TEXT_PP(0);
 	TimestampTz timestamp = PG_GETARG_TIMESTAMPTZ(1);
-	float8		result;
+	int64		intresult;
 	Timestamp	epoch;
 	int			tz;
 	int			type,
 				val;
 	char	   *lowunits;
-	double		dummy;
 	fsec_t		fsec;
 	struct pg_tm tt,
 			   *tm = &tt;
@@ -4820,11 +4900,28 @@ timestamptz_part(PG_FUNCTION_ARGS)
 
 	if (TIMESTAMP_NOT_FINITE(timestamp))
 	{
-		result = NonFiniteTimestampTzPart(type, val, lowunits,
-										  TIMESTAMP_IS_NOBEGIN(timestamp),
-										  true);
-		if (result)
-			PG_RETURN_FLOAT8(result);
+		double		r = NonFiniteTimestampTzPart(type, val, lowunits,
+												 TIMESTAMP_IS_NOBEGIN(timestamp),
+												 true);
+
+		if (r)
+		{
+			if (retnumeric)
+			{
+				if (r < 0)
+					return DirectFunctionCall3(numeric_in,
+											   CStringGetDatum("-Infinity"),
+											   ObjectIdGetDatum(InvalidOid),
+											   Int32GetDatum(-1));
+				else if (r > 0)
+					return DirectFunctionCall3(numeric_in,
+											   CStringGetDatum("Infinity"),
+											   ObjectIdGetDatum(InvalidOid),
+											   Int32GetDatum(-1));
+			}
+			else
+				PG_RETURN_FLOAT8(r);
+		}
 		else
 			PG_RETURN_NULL();
 	}
@@ -4839,111 +4936,129 @@ timestamptz_part(PG_FUNCTION_ARGS)
 		switch (val)
 		{
 			case DTK_TZ:
-				result = -tz;
+				intresult = -tz;
 				break;
 
 			case DTK_TZ_MINUTE:
-				result = -tz;
-				result /= SECS_PER_MINUTE;
-				FMODULO(result, dummy, (double) MINS_PER_HOUR);
+				intresult = (-tz / SECS_PER_MINUTE) % MINS_PER_HOUR;
 				break;
 
 			case DTK_TZ_HOUR:
-				dummy = -tz;
-				FMODULO(dummy, result, (double) SECS_PER_HOUR);
+				intresult = -tz / SECS_PER_HOUR;
 				break;
 
 			case DTK_MICROSEC:
-				result = tm->tm_sec * 1000000.0 + fsec;
+				intresult = tm->tm_sec * 1000000 + fsec;
 				break;
 
 			case DTK_MILLISEC:
-				result = tm->tm_sec * 1000.0 + fsec / 1000.0;
+				if (retnumeric)
+					/*---
+					 * tm->tm_sec * 1000 + fsec / 1000
+					 * = (tm->tm_sec * 1'000'000 + fsec) / 1000
+					 */
+					PG_RETURN_NUMERIC(int64_div_fast_to_numeric(tm->tm_sec * 1000000LL + fsec, 3));
+				else
+					PG_RETURN_FLOAT8(tm->tm_sec * 1000.0 + fsec / 1000.0);
 				break;
 
 			case DTK_SECOND:
-				result = tm->tm_sec + fsec / 1000000.0;
+				if (retnumeric)
+					/*---
+					 * tm->tm_sec + fsec / 1'000'000
+					 * = (tm->tm_sec * 1'000'000 + fsec) / 1'000'000
+					 */
+					PG_RETURN_NUMERIC(int64_div_fast_to_numeric(tm->tm_sec * 1000000LL + fsec, 6));
+				else
+					PG_RETURN_FLOAT8(tm->tm_sec + fsec / 1000000.0);
 				break;
 
 			case DTK_MINUTE:
-				result = tm->tm_min;
+				intresult = tm->tm_min;
 				break;
 
 			case DTK_HOUR:
-				result = tm->tm_hour;
+				intresult = tm->tm_hour;
 				break;
 
 			case DTK_DAY:
-				result = tm->tm_mday;
+				intresult = tm->tm_mday;
 				break;
 
 			case DTK_MONTH:
-				result = tm->tm_mon;
+				intresult = tm->tm_mon;
 				break;
 
 			case DTK_QUARTER:
-				result = (tm->tm_mon - 1) / 3 + 1;
+				intresult = (tm->tm_mon - 1) / 3 + 1;
 				break;
 
 			case DTK_WEEK:
-				result = (float8) date2isoweek(tm->tm_year, tm->tm_mon, tm->tm_mday);
+				intresult = date2isoweek(tm->tm_year, tm->tm_mon, tm->tm_mday);
 				break;
 
 			case DTK_YEAR:
 				if (tm->tm_year > 0)
-					result = tm->tm_year;
+					intresult = tm->tm_year;
 				else
 					/* there is no year 0, just 1 BC and 1 AD */
-					result = tm->tm_year - 1;
+					intresult = tm->tm_year - 1;
 				break;
 
 			case DTK_DECADE:
 				/* see comments in timestamp_part */
 				if (tm->tm_year > 0)
-					result = tm->tm_year / 10;
+					intresult = tm->tm_year / 10;
 				else
-					result = -((8 - (tm->tm_year - 1)) / 10);
+					intresult = -((8 - (tm->tm_year - 1)) / 10);
 				break;
 
 			case DTK_CENTURY:
 				/* see comments in timestamp_part */
 				if (tm->tm_year > 0)
-					result = (tm->tm_year + 99) / 100;
+					intresult = (tm->tm_year + 99) / 100;
 				else
-					result = -((99 - (tm->tm_year - 1)) / 100);
+					intresult = -((99 - (tm->tm_year - 1)) / 100);
 				break;
 
 			case DTK_MILLENNIUM:
 				/* see comments in timestamp_part */
 				if (tm->tm_year > 0)
-					result = (tm->tm_year + 999) / 1000;
+					intresult = (tm->tm_year + 999) / 1000;
 				else
-					result = -((999 - (tm->tm_year - 1)) / 1000);
+					intresult = -((999 - (tm->tm_year - 1)) / 1000);
 				break;
 
 			case DTK_JULIAN:
-				result = date2j(tm->tm_year, tm->tm_mon, tm->tm_mday);
-				result += ((((tm->tm_hour * MINS_PER_HOUR) + tm->tm_min) * SECS_PER_MINUTE) +
-						   tm->tm_sec + (fsec / 1000000.0)) / (double) SECS_PER_DAY;
+				if (retnumeric)
+					PG_RETURN_NUMERIC(numeric_add_opt_error(int64_to_numeric(date2j(tm->tm_year, tm->tm_mon, tm->tm_mday)),
+															numeric_div_opt_error(int64_to_numeric(((((tm->tm_hour * MINS_PER_HOUR) + tm->tm_min) * SECS_PER_MINUTE) + tm->tm_sec) * 1000000LL + fsec),
+																				  int64_to_numeric(SECS_PER_DAY * 1000000LL),
+																				  NULL),
+															NULL));
+				else
+					PG_RETURN_FLOAT8(date2j(tm->tm_year, tm->tm_mon, tm->tm_mday) +
+									 ((((tm->tm_hour * MINS_PER_HOUR) + tm->tm_min) * SECS_PER_MINUTE) +
+									  tm->tm_sec + (fsec / 1000000.0)) / (double) SECS_PER_DAY);
 				break;
 
 			case DTK_ISOYEAR:
-				result = date2isoyear(tm->tm_year, tm->tm_mon, tm->tm_mday);
+				intresult = date2isoyear(tm->tm_year, tm->tm_mon, tm->tm_mday);
 				/* Adjust BC years */
-				if (result <= 0)
-					result -= 1;
+				if (intresult <= 0)
+					intresult -= 1;
 				break;
 
 			case DTK_DOW:
 			case DTK_ISODOW:
-				result = j2day(date2j(tm->tm_year, tm->tm_mon, tm->tm_mday));
-				if (val == DTK_ISODOW && result == 0)
-					result = 7;
+				intresult = j2day(date2j(tm->tm_year, tm->tm_mon, tm->tm_mday));
+				if (val == DTK_ISODOW && intresult == 0)
+					intresult = 7;
 				break;
 
 			case DTK_DOY:
-				result = (date2j(tm->tm_year, tm->tm_mon, tm->tm_mday)
-						  - date2j(tm->tm_year, 1, 1) + 1);
+				intresult = (date2j(tm->tm_year, tm->tm_mon, tm->tm_mday)
+							 - date2j(tm->tm_year, 1, 1) + 1);
 				break;
 
 			default:
@@ -4951,7 +5066,7 @@ timestamptz_part(PG_FUNCTION_ARGS)
 						(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
 						 errmsg("timestamp with time zone units \"%s\" not supported",
 								lowunits)));
-				result = 0;
+				intresult = 0;
 		}
 
 	}
@@ -4961,11 +5076,37 @@ timestamptz_part(PG_FUNCTION_ARGS)
 		{
 			case DTK_EPOCH:
 				epoch = SetEpochTimestamp();
-				/* try to avoid precision loss in subtraction */
-				if (timestamp < (PG_INT64_MAX + epoch))
-					result = (timestamp - epoch) / 1000000.0;
+				/* (timestamp - epoch) / 1000000 */
+				if (retnumeric)
+				{
+					Numeric		result;
+
+					if (timestamp < (PG_INT64_MAX + epoch))
+						result = int64_div_fast_to_numeric(timestamp - epoch, 6);
+					else
+					{
+						result = numeric_div_opt_error(numeric_sub_opt_error(int64_to_numeric(timestamp),
+																			 int64_to_numeric(epoch),
+																			 NULL),
+													   int64_to_numeric(1000000),
+													   NULL);
+						result = DatumGetNumeric(DirectFunctionCall2(numeric_round,
+																	 NumericGetDatum(result),
+																	 Int32GetDatum(6)));
+					}
+					PG_RETURN_NUMERIC(result);
+				}
 				else
-					result = ((float8) timestamp - epoch) / 1000000.0;
+				{
+					float8		result;
+
+					/* try to avoid precision loss in subtraction */
+					if (timestamp < (PG_INT64_MAX + epoch))
+						result = (timestamp - epoch) / 1000000.0;
+					else
+						result = ((float8) timestamp - epoch) / 1000000.0;
+					PG_RETURN_FLOAT8(result);
+				}
 				break;
 
 			default:
@@ -4973,7 +5114,7 @@ timestamptz_part(PG_FUNCTION_ARGS)
 						(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
 						 errmsg("timestamp with time zone units \"%s\" not supported",
 								lowunits)));
-				result = 0;
+				intresult = 0;
 		}
 	}
 	else
@@ -4983,22 +5124,37 @@ timestamptz_part(PG_FUNCTION_ARGS)
 				 errmsg("timestamp with time zone units \"%s\" not recognized",
 						lowunits)));
 
-		result = 0;
+		intresult = 0;
 	}
 
-	PG_RETURN_FLOAT8(result);
+	if (retnumeric)
+		PG_RETURN_NUMERIC(int64_to_numeric(intresult));
+	else
+		PG_RETURN_FLOAT8(intresult);
+}
+
+Datum
+timestamptz_part(PG_FUNCTION_ARGS)
+{
+	return timestamptz_part_common(fcinfo, false);
+}
+
+Datum
+extract_timestamptz(PG_FUNCTION_ARGS)
+{
+	return timestamptz_part_common(fcinfo, true);
 }
 
 
-/* interval_part()
+/* interval_part() and extract_interval()
  * Extract specified field from interval.
  */
-Datum
-interval_part(PG_FUNCTION_ARGS)
+static Datum
+interval_part_common(PG_FUNCTION_ARGS, bool retnumeric)
 {
 	text	   *units = PG_GETARG_TEXT_PP(0);
 	Interval   *interval = PG_GETARG_INTERVAL_P(1);
-	float8		result;
+	int64		intresult;
 	int			type,
 				val;
 	char	   *lowunits;
@@ -5021,54 +5177,68 @@ interval_part(PG_FUNCTION_ARGS)
 			switch (val)
 			{
 				case DTK_MICROSEC:
-					result = tm->tm_sec * 1000000.0 + fsec;
+					intresult = tm->tm_sec * 1000000 + fsec;
 					break;
 
 				case DTK_MILLISEC:
-					result = tm->tm_sec * 1000.0 + fsec / 1000.0;
+					if (retnumeric)
+						/*---
+						 * tm->tm_sec * 1000 + fsec / 1000
+						 * = (tm->tm_sec * 1'000'000 + fsec) / 1000
+						 */
+						PG_RETURN_NUMERIC(int64_div_fast_to_numeric(tm->tm_sec * 1000000LL + fsec, 3));
+					else
+						PG_RETURN_FLOAT8(tm->tm_sec * 1000.0 + fsec / 1000.0);
 					break;
 
 				case DTK_SECOND:
-					result = tm->tm_sec + fsec / 1000000.0;
+					if (retnumeric)
+						/*---
+						 * tm->tm_sec + fsec / 1'000'000
+						 * = (tm->tm_sec * 1'000'000 + fsec) / 1'000'000
+						 */
+						PG_RETURN_NUMERIC(int64_div_fast_to_numeric(tm->tm_sec * 1000000LL + fsec, 6));
+					else
+						PG_RETURN_FLOAT8(tm->tm_sec + fsec / 1000000.0);
 					break;
 
 				case DTK_MINUTE:
-					result = tm->tm_min;
+					intresult = tm->tm_min;
 					break;
 
 				case DTK_HOUR:
-					result = tm->tm_hour;
+					intresult = tm->tm_hour;
 					break;
 
 				case DTK_DAY:
-					result = tm->tm_mday;
+					intresult = tm->tm_mday;
 					break;
 
 				case DTK_MONTH:
-					result = tm->tm_mon;
+					intresult = tm->tm_mon;
 					break;
 
 				case DTK_QUARTER:
-					result = (tm->tm_mon / 3) + 1;
+					intresult = (tm->tm_mon / 3) + 1;
 					break;
 
 				case DTK_YEAR:
-					result = tm->tm_year;
+					intresult = tm->tm_year;
 					break;
 
 				case DTK_DECADE:
 					/* caution: C division may have negative remainder */
-					result = tm->tm_year / 10;
+					intresult = tm->tm_year / 10;
 					break;
 
 				case DTK_CENTURY:
 					/* caution: C division may have negative remainder */
-					result = tm->tm_year / 100;
+					intresult = tm->tm_year / 100;
 					break;
 
 				case DTK_MILLENNIUM:
 					/* caution: C division may have negative remainder */
-					result = tm->tm_year / 1000;
+					intresult = tm->tm_year / 1000;
 					break;
 
 				default:
@@ -5076,22 +5246,60 @@ interval_part(PG_FUNCTION_ARGS)
 							(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
 							 errmsg("interval units \"%s\" not supported",
 									lowunits)));
-					result = 0;
+					intresult = 0;
 			}
-
 		}
 		else
 		{
 			elog(ERROR, "could not convert interval to tm");
-			result = 0;
+			intresult = 0;
 		}
 	}
 	else if (type == RESERV && val == DTK_EPOCH)
 	{
-		result = interval->time / 1000000.0;
-		result += ((double) DAYS_PER_YEAR * SECS_PER_DAY) * (interval->month / MONTHS_PER_YEAR);
-		result += ((double) DAYS_PER_MONTH * SECS_PER_DAY) * (interval->month % MONTHS_PER_YEAR);
-		result += ((double) SECS_PER_DAY) * interval->day;
+		if (retnumeric)
+		{
+			Numeric		result;
+			int64		secs_from_day_month;
+			int64		val;
+
+			/* this always fits into int64 */
+			secs_from_day_month = ((int64) DAYS_PER_YEAR * (interval->month / MONTHS_PER_YEAR) +
+								   (int64) DAYS_PER_MONTH * (interval->month % MONTHS_PER_YEAR) +
+								   interval->day) * SECS_PER_DAY;
+
+			/*---
+			 * result = secs_from_day_month + interval->time / 1'000'000
+			 * = (secs_from_day_month * 1'000'000 + interval->time) / 1'000'000
+			 */
+
+			/*
+			 * Try the computation inside int64; if it overflows, do it in
+			 * numeric (slower).  This overflow happens around 10^9 days, so
+			 * not common in practice.
+			 */
+			if (!pg_mul_s64_overflow(secs_from_day_month, 1000000, &val) &&
+				!pg_add_s64_overflow(val, interval->time, &val))
+				result = int64_div_fast_to_numeric(val, 6);
+			else
+				result =
+					numeric_add_opt_error(int64_div_fast_to_numeric(interval->time, 6),
+										  int64_to_numeric(secs_from_day_month),
+										  NULL);
+
+			PG_RETURN_NUMERIC(result);
+		}
+		else
+		{
+			float8		result;
+
+			result = interval->time / 1000000.0;
+			result += ((double) DAYS_PER_YEAR * SECS_PER_DAY) * (interval->month / MONTHS_PER_YEAR);
+			result += ((double) DAYS_PER_MONTH * SECS_PER_DAY) * (interval->month % MONTHS_PER_YEAR);
+			result += ((double) SECS_PER_DAY) * interval->day;
+
+			PG_RETURN_FLOAT8(result);
+		}
 	}
 	else
 	{
@@ -5099,10 +5307,25 @@ interval_part(PG_FUNCTION_ARGS)
 				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
 				 errmsg("interval units \"%s\" not recognized",
 						lowunits)));
-		result = 0;
+		intresult = 0;
 	}
 
-	PG_RETURN_FLOAT8(result);
+	if (retnumeric)
+		PG_RETURN_NUMERIC(int64_to_numeric(intresult));
+	else
+		PG_RETURN_FLOAT8(intresult);
+}
+
+Datum
+interval_part(PG_FUNCTION_ARGS)
+{
+	return interval_part_common(fcinfo, false);
+}
+
+Datum
+extract_interval(PG_FUNCTION_ARGS)
+{
+	return interval_part_common(fcinfo, true);
 }