Add a timezone-specific variant of date_trunc().

date_trunc(field, timestamptz, zone_name) performs truncation using
the named time zone as reference, rather than working in the session
time zone as is the default behavior.  It's equivalent to

date_trunc(field, timestamptz at time zone zone_name) at time zone zone_name

but it's faster, easier to type, and arguably easier to understand.

Vik Fearing and Tom Lane

Discussion: https://postgr.es/m/[email protected]

5 files changed, 121 insertions, 19 deletions

diff --git a/src/backend/utils/adt/timestamp.c b/src/backend/utils/adt/timestamp.c
index 449164ae7e5..b377c38c8af 100644
--- a/src/backend/utils/adt/timestamp.c
+++ b/src/backend/utils/adt/timestamp.c
@@ -3925,14 +3925,15 @@ timestamp_trunc(PG_FUNCTION_ARGS)
 	PG_RETURN_TIMESTAMP(result);
 }
 
-/* timestamptz_trunc()
- * Truncate timestamp to specified units.
+/*
+ * Common code for timestamptz_trunc() and timestamptz_trunc_zone().
+ *
+ * tzp identifies the zone to truncate with respect to.  We assume
+ * infinite timestamps have already been rejected.
  */
-Datum
-timestamptz_trunc(PG_FUNCTION_ARGS)
+static TimestampTz
+timestamptz_trunc_internal(text *units, TimestampTz timestamp, pg_tz *tzp)
 {
-	text	   *units = PG_GETARG_TEXT_PP(0);
-	TimestampTz timestamp = PG_GETARG_TIMESTAMPTZ(1);
 	TimestampTz result;
 	int			tz;
 	int			type,
@@ -3943,9 +3944,6 @@ timestamptz_trunc(PG_FUNCTION_ARGS)
 	struct pg_tm tt,
 			   *tm = &tt;
 
-	if (TIMESTAMP_NOT_FINITE(timestamp))
-		PG_RETURN_TIMESTAMPTZ(timestamp);
-
 	lowunits = downcase_truncate_identifier(VARDATA_ANY(units),
 											VARSIZE_ANY_EXHDR(units),
 											false);
@@ -3954,7 +3952,7 @@ timestamptz_trunc(PG_FUNCTION_ARGS)
 
 	if (type == UNITS)
 	{
-		if (timestamp2tm(timestamp, &tz, tm, &fsec, NULL, NULL) != 0)
+		if (timestamp2tm(timestamp, &tz, tm, &fsec, NULL, tzp) != 0)
 			ereport(ERROR,
 					(errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
 					 errmsg("timestamp out of range")));
@@ -4055,7 +4053,7 @@ timestamptz_trunc(PG_FUNCTION_ARGS)
 		}
 
 		if (redotz)
-			tz = DetermineTimeZoneOffset(tm, session_timezone);
+			tz = DetermineTimeZoneOffset(tm, tzp);
 
 		if (tm2timestamp(tm, fsec, &tz, &result) != 0)
 			ereport(ERROR,
@@ -4071,6 +4069,83 @@ timestamptz_trunc(PG_FUNCTION_ARGS)
 		result = 0;
 	}
 
+	return result;
+}
+
+/* timestamptz_trunc()
+ * Truncate timestamptz to specified units in session timezone.
+ */
+Datum
+timestamptz_trunc(PG_FUNCTION_ARGS)
+{
+	text	   *units = PG_GETARG_TEXT_PP(0);
+	TimestampTz timestamp = PG_GETARG_TIMESTAMPTZ(1);
+	TimestampTz result;
+
+	if (TIMESTAMP_NOT_FINITE(timestamp))
+		PG_RETURN_TIMESTAMPTZ(timestamp);
+
+	result = timestamptz_trunc_internal(units, timestamp, session_timezone);
+
+	PG_RETURN_TIMESTAMPTZ(result);
+}
+
+/* timestamptz_trunc_zone()
+ * Truncate timestamptz to specified units in specified timezone.
+ */
+Datum
+timestamptz_trunc_zone(PG_FUNCTION_ARGS)
+{
+	text	   *units = PG_GETARG_TEXT_PP(0);
+	TimestampTz timestamp = PG_GETARG_TIMESTAMPTZ(1);
+	text	   *zone = PG_GETARG_TEXT_PP(2);
+	TimestampTz result;
+	char		tzname[TZ_STRLEN_MAX + 1];
+	char	   *lowzone;
+	int			type,
+				val;
+	pg_tz	   *tzp;
+
+	/*
+	 * timestamptz_zone() doesn't look up the zone for infinite inputs, so we
+	 * don't do so here either.
+	 */
+	if (TIMESTAMP_NOT_FINITE(timestamp))
+		PG_RETURN_TIMESTAMP(timestamp);
+
+	/*
+	 * Look up the requested timezone (see notes in timestamptz_zone()).
+	 */
+	text_to_cstring_buffer(zone, tzname, sizeof(tzname));
+
+	/* DecodeTimezoneAbbrev requires lowercase input */
+	lowzone = downcase_truncate_identifier(tzname,
+										   strlen(tzname),
+										   false);
+
+	type = DecodeTimezoneAbbrev(0, lowzone, &val, &tzp);
+
+	if (type == TZ || type == DTZ)
+	{
+		/* fixed-offset abbreviation, get a pg_tz descriptor for that */
+		tzp = pg_tzset_offset(-val);
+	}
+	else if (type == DYNTZ)
+	{
+		/* dynamic-offset abbreviation, use its referenced timezone */
+	}
+	else
+	{
+		/* try it as a full zone name */
+		tzp = pg_tzset(tzname);
+		if (!tzp)
+			ereport(ERROR,
+					(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+					 errmsg("time zone \"%s\" not recognized", tzname)));
+	}
+
+	result = timestamptz_trunc_internal(units, timestamp, tzp);
+
 	PG_RETURN_TIMESTAMPTZ(result);
 }
 
diff --git a/src/include/catalog/catversion.h b/src/include/catalog/catversion.h
index 7d78cbe026a..a307a2ba767 100644
--- a/src/include/catalog/catversion.h
+++ b/src/include/catalog/catversion.h
@@ -53,6 +53,6 @@
  */
 
 /*							yyyymmddN */
-#define CATALOG_VERSION_NO	201811061
+#define CATALOG_VERSION_NO	201811141
 
 #endif
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 4026018ba9d..9264a2e9872 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -2280,6 +2280,10 @@
   descr => 'truncate timestamp with time zone to specified units',
   proname => 'date_trunc', provolatile => 's', prorettype => 'timestamptz',
   proargtypes => 'text timestamptz', prosrc => 'timestamptz_trunc' },
+{ oid => '1284',
+  descr => 'truncate timestamp with time zone to specified units in specified time zone',
+  proname => 'date_trunc', provolatile => 's', prorettype => 'timestamptz',
+  proargtypes => 'text timestamptz text', prosrc => 'timestamptz_trunc_zone' },
 { oid => '1218', descr => 'truncate interval to specified units',
   proname => 'date_trunc', prorettype => 'interval',
   proargtypes => 'text interval', prosrc => 'interval_trunc' },
@@ -5825,8 +5829,8 @@
   prorettype => 'timestamptz', proargtypes => '',
   prosrc => 'pg_backup_start_time' },
 { oid => '3436', descr => 'promote standby server',
-  proname => 'pg_promote', provolatile => 'v',
-  prorettype => 'bool', proargtypes => 'bool int4', proargnames => '{wait,wait_seconds}',
+  proname => 'pg_promote', provolatile => 'v', prorettype => 'bool',
+  proargtypes => 'bool int4', proargnames => '{wait,wait_seconds}',
   prosrc => 'pg_promote' },
 { oid => '2848', descr => 'switch to new wal file',
   proname => 'pg_switch_wal', provolatile => 'v', prorettype => 'pg_lsn',
@@ -10007,10 +10011,11 @@
   proallargtypes => '{text,int8,timestamptz}', proargmodes => '{o,o,o}',
   proargnames => '{name,size,modification}', prosrc => 'pg_ls_waldir' },
 { oid => '5031', descr => 'list of files in the archive_status directory',
-  proname => 'pg_ls_archive_statusdir', procost => '10', prorows => '20', proretset => 't',
-  provolatile => 'v', prorettype => 'record', proargtypes => '',
-  proallargtypes => '{text,int8,timestamptz}', proargmodes => '{o,o,o}',
-  proargnames => '{name,size,modification}', prosrc => 'pg_ls_archive_statusdir' },
+  proname => 'pg_ls_archive_statusdir', procost => '10', prorows => '20',
+  proretset => 't', provolatile => 'v', prorettype => 'record',
+  proargtypes => '', proallargtypes => '{text,int8,timestamptz}',
+  proargmodes => '{o,o,o}', proargnames => '{name,size,modification}',
+  prosrc => 'pg_ls_archive_statusdir' },
 { oid => '5029', descr => 'list files in the pgsql_tmp directory',
   proname => 'pg_ls_tmpdir', procost => '10', prorows => '20', proretset => 't',
   provolatile => 'v', prorettype => 'record', proargtypes => '',
@@ -10036,6 +10041,6 @@
   proallargtypes => '{regclass,regclass,regclass,bool,int4}',
   proargmodes => '{i,o,o,o,o}',
   proargnames => '{rootrelid,relid,parentrelid,isleaf,level}',
-  prosrc => 'pg_partition_tree' }
+  prosrc => 'pg_partition_tree' },
 
 ]
diff --git a/src/test/regress/expected/timestamptz.out b/src/test/regress/expected/timestamptz.out
index 2340f307942..8a4c7199934 100644
--- a/src/test/regress/expected/timestamptz.out
+++ b/src/test/regress/expected/timestamptz.out
@@ -649,6 +649,24 @@ SELECT '' AS date_trunc_week, date_trunc( 'week', timestamp with time zone '2004
                  | Mon Feb 23 00:00:00 2004 PST
 (1 row)
 
+SELECT '' AS date_trunc_at_tz, date_trunc('day', timestamp with time zone '2001-02-16 20:38:40+00', 'Australia/Sydney') as sydney_trunc;  -- zone name
+ date_trunc_at_tz |         sydney_trunc         
+------------------+------------------------------
+                  | Fri Feb 16 05:00:00 2001 PST
+(1 row)
+
+SELECT '' AS date_trunc_at_tz, date_trunc('day', timestamp with time zone '2001-02-16 20:38:40+00', 'GMT') as gmt_trunc;  -- fixed-offset abbreviation
+ date_trunc_at_tz |          gmt_trunc           
+------------------+------------------------------
+                  | Thu Feb 15 16:00:00 2001 PST
+(1 row)
+
+SELECT '' AS date_trunc_at_tz, date_trunc('day', timestamp with time zone '2001-02-16 20:38:40+00', 'VET') as vet_trunc;  -- variable-offset abbreviation
+ date_trunc_at_tz |          vet_trunc           
+------------------+------------------------------
+                  | Thu Feb 15 20:00:00 2001 PST
+(1 row)
+
 -- Test casting within a BETWEEN qualifier
 SELECT '' AS "54", d1 - timestamp with time zone '1997-01-02' AS diff
   FROM TIMESTAMPTZ_TBL
diff --git a/src/test/regress/sql/timestamptz.sql b/src/test/regress/sql/timestamptz.sql
index f17d153fccb..c3bd46c2331 100644
--- a/src/test/regress/sql/timestamptz.sql
+++ b/src/test/regress/sql/timestamptz.sql
@@ -193,6 +193,10 @@ SELECT '' AS "54", d1 - timestamp with time zone '1997-01-02' AS diff
 
 SELECT '' AS date_trunc_week, date_trunc( 'week', timestamp with time zone '2004-02-29 15:44:17.71393' ) AS week_trunc;
 
+SELECT '' AS date_trunc_at_tz, date_trunc('day', timestamp with time zone '2001-02-16 20:38:40+00', 'Australia/Sydney') as sydney_trunc;  -- zone name
+SELECT '' AS date_trunc_at_tz, date_trunc('day', timestamp with time zone '2001-02-16 20:38:40+00', 'GMT') as gmt_trunc;  -- fixed-offset abbreviation
+SELECT '' AS date_trunc_at_tz, date_trunc('day', timestamp with time zone '2001-02-16 20:38:40+00', 'VET') as vet_trunc;  -- variable-offset abbreviation
+
 -- Test casting within a BETWEEN qualifier
 SELECT '' AS "54", d1 - timestamp with time zone '1997-01-02' AS diff
   FROM TIMESTAMPTZ_TBL