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Add a timezone-specific variant of date_trunc().

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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/6249ffc4-2b22-4c1b-4e7d-7af84fedd7c6@2ndquadrant.com
This commit is contained in:
Tom Lane 2018-11-14 15:41:07 -05:00
parent 06c723447b
commit 600b04d6b5
6 changed files with 166 additions and 27 deletions
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53
doc/src/sgml/func.sgml
View File

@ -7179,16 +7179,25 @@ SELECT regexp_match('abc01234xyz', '(?:(.*?)(\d+)(.*)){1,1}');
<literal><function>date_trunc(<type>text</type>, <type>timestamp</type>)</function></literal>
</entry>
<entry><type>timestamp</type></entry>
<entry>Truncate to specified precision; see also <xref linkend="functions-datetime-trunc"/>
<entry>Truncate to specified precision; see <xref linkend="functions-datetime-trunc"/>
</entry>
<entry><literal>date_trunc('hour', timestamp '2001-02-16 20:38:40')</literal></entry>
<entry><literal>2001-02-16 20:00:00</literal></entry>
</row>
<row>
<entry><literal><function>date_trunc(<type>text</type>, <type>timestamp with time zone</type>, <type>text</type>)</function></literal></entry>
<entry><type>timestamp with time zone</type></entry>
<entry>Truncate to specified precision in the specified time zone; see <xref linkend="functions-datetime-trunc"/>
</entry>
<entry><literal>date_trunc('day', timestamptz '2001-02-16 20:38:40+00', 'Australia/Sydney')</literal></entry>
<entry><literal>2001-02-16 13:00:00+00</literal></entry>
</row>
<row>
<entry><literal><function>date_trunc(<type>text</type>, <type>interval</type>)</function></literal></entry>
<entry><type>interval</type></entry>
<entry>Truncate to specified precision; see also <xref linkend="functions-datetime-trunc"/>
<entry>Truncate to specified precision; see <xref linkend="functions-datetime-trunc"/>
</entry>
<entry><literal>date_trunc('hour', interval '2 days 3 hours 40 minutes')</literal></entry>
<entry><literal>2 days 03:00:00</literal></entry>
@ -8078,17 +8087,19 @@ SELECT date_part('hour', INTERVAL '4 hours 3 minutes');
<para>
<synopsis>
date_trunc('<replaceable>field</replaceable>', <replaceable>source</replaceable>)
date_trunc(<replaceable>field</replaceable>, <replaceable>source</replaceable> [, <replaceable>time_zone</replaceable> ])
</synopsis>
<replaceable>source</replaceable> is a value expression of type
<type>timestamp</type> or <type>interval</type>.
<type>timestamp</type>, <type>timestamp with time zone</type>,
or <type>interval</type>.
(Values of type <type>date</type> and
<type>time</type> are cast automatically to <type>timestamp</type> or
<type>interval</type>, respectively.)
<replaceable>field</replaceable> selects to which precision to
truncate the input value. The return value is of type
<type>timestamp</type> or <type>interval</type>
with all fields that are less significant than the
truncate the input value. The return value is likewise of type
<type>timestamp</type>, <type>timestamp with time zone</type>,
or <type>interval</type>,
and it has all fields that are less significant than the
selected one set to zero (or one, for day and month).
</para>
@ -8112,13 +8123,39 @@ date_trunc('<replaceable>field</replaceable>', <replaceable>source</replaceable>
</para>
<para>
Examples:
When the input value is of type <type>timestamp with time zone</type>,
the truncation is performed with respect to a particular time zone;
for example, truncation to <literal>day</literal> produces a value that
is midnight in that zone. By default, truncation is done with respect
to the current <xref linkend="guc-timezone"/> setting, but the
optional <replaceable>time_zone</replaceable> argument can be provided
to specify a different time zone. The time zone name can be specified
in any of the ways described in <xref linkend="datatype-timezones"/>.
</para>
<para>
A time zone cannot be specified when processing <type>timestamp without
time zone</type> or <type>interval</type> inputs. These are always
taken at face value.
</para>
<para>
Examples (assuming the local time zone is <literal>America/New_York</literal>):
<screen>
SELECT date_trunc('hour', TIMESTAMP '2001-02-16 20:38:40');
<lineannotation>Result: </lineannotation><computeroutput>2001-02-16 20:00:00</computeroutput>
SELECT date_trunc('year', TIMESTAMP '2001-02-16 20:38:40');
<lineannotation>Result: </lineannotation><computeroutput>2001-01-01 00:00:00</computeroutput>
SELECT date_trunc('day', TIMESTAMP WITH TIME ZONE '2001-02-16 20:38:40+00');
<lineannotation>Result: </lineannotation><computeroutput>2001-02-16 00:00:00-05</computeroutput>
SELECT date_trunc('day', TIMESTAMP WITH TIME ZONE '2001-02-16 20:38:40+00', 'Australia/Sydney');
<lineannotation>Result: </lineannotation><computeroutput>2001-02-16 08:00:00-05</computeroutput>
SELECT date_trunc('hour', INTERVAL '3 days 02:47:33');
<lineannotation>Result: </lineannotation><computeroutput>3 days 02:00:00</computeroutput>
</screen>
</para>
</sect2>

97
src/backend/utils/adt/timestamp.c
View File

@ -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);
}

2
src/include/catalog/catversion.h
View File

@ -53,6 +53,6 @@
*/
/* yyyymmddN */
#define CATALOG_VERSION_NO 201811061
#define CATALOG_VERSION_NO 201811141
#endif

19
src/include/catalog/pg_proc.dat
View File

@ -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' },
]

18
src/test/regress/expected/timestamptz.out
View File

@ -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

4
src/test/regress/sql/timestamptz.sql
View File

@ -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