The Standard defines time zone conversion as follows:
<datetime factor> ::=
<datetime primary> [ <time zone> ]
<time zone> ::=
AT <time zone specifier>
<time zone specifier> ::=
LOCAL
| TIME ZONE <interval primary>
While looking at something else, I noticed we do not support AT LOCAL.
The local time zone is defined as that of *the session*, not the server,
which can make this quite interesting in views where the view will
automatically adjust to the session's time zone.
Patch against 3f1aaaa180 attached.
--
Vik Fearing
From b8317f3070c11df1e2ad791bd8d823aaae66dbe4 Mon Sep 17 00:00:00 2001
From: Vik Fearing <[email protected]>
Date: Mon, 5 Jun 2023 19:42:42 -0400
Subject: [PATCH v1] Add support for AT LOCAL
When converting a timestamp to/from with/without time zone, the SQL
Standard specifies an AT LOCAL variant of AT TIME ZONE which uses the
session's time zone.
---
doc/src/sgml/func.sgml | 13 +++++++
src/backend/parser/gram.y | 12 ++++++
src/backend/utils/adt/ruleutils.c | 43 ++++++++++++++++++---
src/test/regress/expected/timestamptz.out | 47 +++++++++++++++++++++++
src/test/regress/sql/timestamptz.sql | 21 ++++++++++
5 files changed, 131 insertions(+), 5 deletions(-)
diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index 5a47ce4343..6d07f063e0 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -10553,14 +10553,18 @@ SELECT date_bin('15 minutes', TIMESTAMP '2020-02-11 15:44:17', TIMESTAMP '2001-0
<secondary>conversion</secondary>
</indexterm>
<indexterm>
<primary>AT TIME ZONE</primary>
</indexterm>
+ <indexterm>
+ <primary>AT LOCAL</primary>
+ </indexterm>
+
<para>
The <literal>AT TIME ZONE</literal> operator converts time
stamp <emphasis>without</emphasis> time zone to/from
time stamp <emphasis>with</emphasis> time zone, and
<type>time with time zone</type> values to different time
zones. <xref linkend="functions-datetime-zoneconvert-table"/> shows its
variants.
@@ -10641,26 +10645,35 @@ SELECT date_bin('15 minutes', TIMESTAMP '2020-02-11 15:44:17', TIMESTAMP '2001-0
or as an interval (e.g., <literal>INTERVAL '-08:00'</literal>).
In the text case, a time zone name can be specified in any of the ways
described in <xref linkend="datatype-timezones"/>.
The interval case is only useful for zones that have fixed offsets from
UTC, so it is not very common in practice.
</para>
+ <para>
+ The syntax <literal>AT LOCAL</literal> may be used as shorthand for <literal>AT TIME ZONE
+ <replaceable>local</replaceable></literal>, where <replaceable>local</replaceable> is the
+ session's <varname>TimeZone</varname> value.
+ </para>
+
<para>
Examples (assuming the current <xref linkend="guc-timezone"/> setting
is <literal>America/Los_Angeles</literal>):
<screen>
SELECT TIMESTAMP '2001-02-16 20:38:40' AT TIME ZONE 'America/Denver';
<lineannotation>Result: </lineannotation><computeroutput>2001-02-16 19:38:40-08</computeroutput>
SELECT TIMESTAMP WITH TIME ZONE '2001-02-16 20:38:40-05' AT TIME ZONE 'America/Denver';
<lineannotation>Result: </lineannotation><computeroutput>2001-02-16 18:38:40</computeroutput>
SELECT TIMESTAMP '2001-02-16 20:38:40' AT TIME ZONE 'Asia/Tokyo' AT TIME ZONE 'America/Chicago';
<lineannotation>Result: </lineannotation><computeroutput>2001-02-16 05:38:40</computeroutput>
+
+SELECT TIMESTAMP WITH TIME ZONE '2001-02-16 20:38:40-05' AT LOCAL;
+<lineannotation>Result: </lineannotation><computeroutput>2001-02-16 17:38:40</computeroutput>
</screen>
The first example adds a time zone to a value that lacks it, and
displays the value using the current <varname>TimeZone</varname>
setting. The second example shifts the time stamp with time zone value
to the specified time zone, and returns the value without a time zone.
This allows storage and display of values different from the current
<varname>TimeZone</varname> setting. The third example converts
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index 39ab7eac0d..2b27904970 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -14414,14 +14414,26 @@ a_expr: c_expr { $$ = $1; }
| a_expr AT TIME ZONE a_expr %prec AT
{
$$ = (Node *) makeFuncCall(SystemFuncName("timezone"),
list_make2($5, $1),
COERCE_SQL_SYNTAX,
@2);
}
+ | a_expr AT LOCAL %prec AT
+ {
+ /* Use the value of the session's time zone */
+ FuncCall *tz = makeFuncCall(SystemFuncName("current_setting"),
+ list_make1(makeStringConst("TimeZone", -1)),
+ COERCE_SQL_SYNTAX,
+ -1);
+ $$ = (Node *) makeFuncCall(SystemFuncName("timezone"),
+ list_make2(tz, $1),
+ COERCE_SQL_SYNTAX,
+ @2);
+ }
/*
* These operators must be called out explicitly in order to make use
* of bison's automatic operator-precedence handling. All other
* operator names are handled by the generic productions using "Op",
* below; and all those operators will have the same precedence.
*
* If you add more explicitly-known operators, be sure to add them
diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index d3a973d86b..1fca65a7f2 100644
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -10313,20 +10313,53 @@ get_func_sql_syntax(FuncExpr *expr, deparse_context *context)
case F_TIMEZONE_INTERVAL_TIMESTAMP:
case F_TIMEZONE_INTERVAL_TIMESTAMPTZ:
case F_TIMEZONE_INTERVAL_TIMETZ:
case F_TIMEZONE_TEXT_TIMESTAMP:
case F_TIMEZONE_TEXT_TIMESTAMPTZ:
case F_TIMEZONE_TEXT_TIMETZ:
/* AT TIME ZONE ... note reversed argument order */
+ Node *ts = (Node *) lsecond(expr->args);
+ Node *zone = (Node *) linitial(expr->args);
+
+ /*
+ * If the time zone is a function call, look to see if this is literally
+ * current_setting('TimeZone') and that we should coerce it to SQL, in which
+ * case we need to use "AT LOCAL".
+ */
+ bool islocal = false;
+
+ /* Is it a function? */
+ if (IsA(zone, FuncExpr))
+ {
+ FuncExpr *func = castNode(FuncExpr, zone);
+
+ /* Is it current_setting() with a constant argument that should be coerced to SQL? */
+ if (func->funcid == F_CURRENT_SETTING_TEXT &&
+ func->funcformat == COERCE_SQL_SYNTAX &&
+ IsA(linitial(func->args), Const))
+ {
+ Const *con = castNode(Const, linitial(func->args));
+
+ Assert(con->consttype == TEXTOID && !con->constisnull);
+
+ /* Is that argument TimeZone? */
+ if (pg_strcasecmp(TextDatumGetCString(con->constvalue), "TimeZone") == 0)
+ islocal = true;
+ }
+ }
+
appendStringInfoChar(buf, '(');
- get_rule_expr_paren((Node *) lsecond(expr->args), context, false,
- (Node *) expr);
- appendStringInfoString(buf, " AT TIME ZONE ");
- get_rule_expr_paren((Node *) linitial(expr->args), context, false,
- (Node *) expr);
+ get_rule_expr_paren(ts, context, false, (Node *) expr);
+ if (islocal)
+ appendStringInfoString(buf, " AT LOCAL");
+ else
+ {
+ appendStringInfoString(buf, " AT TIME ZONE ");
+ get_rule_expr_paren(zone, context, false, (Node *) expr);
+ }
appendStringInfoChar(buf, ')');
return true;
case F_OVERLAPS_TIMESTAMPTZ_INTERVAL_TIMESTAMPTZ_INTERVAL:
case F_OVERLAPS_TIMESTAMPTZ_INTERVAL_TIMESTAMPTZ_TIMESTAMPTZ:
case F_OVERLAPS_TIMESTAMPTZ_TIMESTAMPTZ_TIMESTAMPTZ_INTERVAL:
case F_OVERLAPS_TIMESTAMPTZ_TIMESTAMPTZ_TIMESTAMPTZ_TIMESTAMPTZ:
diff --git a/src/test/regress/expected/timestamptz.out b/src/test/regress/expected/timestamptz.out
index 0dd2fe2c82..ae55e63077 100644
--- a/src/test/regress/expected/timestamptz.out
+++ b/src/test/regress/expected/timestamptz.out
@@ -3131,14 +3131,61 @@ SELECT '2014-10-25 22:00:01 UTC'::timestamptz AT TIME ZONE 'MSK';
SELECT '2014-10-25 23:00:00 UTC'::timestamptz AT TIME ZONE 'MSK';
timezone
--------------------------
Sun Oct 26 02:00:00 2014
(1 row)
+--
+-- Test LOCAL time zone
+--
+BEGIN;
+SET LOCAL TIME ZONE 'Europe/Paris';
+VALUES (CAST('1978-07-07 19:38 America/New_York' AS TIMESTAMP WITH TIME ZONE) AT LOCAL);
+ column1
+--------------------------
+ Sat Jul 08 01:38:00 1978
+(1 row)
+
+VALUES (TIMESTAMP '1978-07-07 19:38' AT LOCAL);
+ column1
+-------------------------------
+ Fri Jul 07 19:38:00 1978 CEST
+(1 row)
+
+SET LOCAL TIME ZONE 'Australia/Sydney';
+VALUES (CAST('1978-07-07 19:38 America/New_York' AS TIMESTAMP WITH TIME ZONE) AT LOCAL);
+ column1
+--------------------------
+ Sat Jul 08 09:38:00 1978
+(1 row)
+
+VALUES (TIMESTAMP '1978-07-07 19:38' AT LOCAL);
+ column1
+-------------------------------
+ Fri Jul 07 19:38:00 1978 AEST
+(1 row)
+
+RESET TIME ZONE;
+CREATE VIEW local_time_zone AS
+ VALUES (CAST('1978-07-07 19:38 America/New_York' AS TIMESTAMP WITH TIME ZONE) AT LOCAL,
+ CAST('1978-07-07 19:38 America/New_York' AS TIMESTAMP WITH TIME ZONE) AT TIME ZONE current_setting('TimeZone'),
+ TIMESTAMP '1978-07-07 19:38' AT LOCAL,
+ TIMESTAMP '1978-07-07 19:38' AT TIME ZONE current_setting('TimeZone'));
+\sv local_time_zone
+CREATE OR REPLACE VIEW public.local_time_zone AS
+ VALUES (('Fri Jul 07 16:38:00 1978 PDT'::timestamp with time zone AT LOCAL),('Fri Jul 07 16:38:00 1978 PDT'::timestamp with time zone AT TIME ZONE current_setting('TimeZone'::text)),('Fri Jul 07 19:38:00 1978'::timestamp without time zone AT LOCAL),('Fri Jul 07 19:38:00 1978'::timestamp without time zone AT TIME ZONE current_setting('TimeZone'::text)))
+TABLE local_time_zone;
+ column1 | column2 | column3 | column4
+--------------------------+--------------------------+------------------------------+------------------------------
+ Fri Jul 07 16:38:00 1978 | Fri Jul 07 16:38:00 1978 | Fri Jul 07 19:38:00 1978 PDT | Fri Jul 07 19:38:00 1978 PDT
+(1 row)
+
+DROP VIEW local_time_zone;
+COMMIT;
--
-- Test that AT TIME ZONE isn't misoptimized when using an index (bug #14504)
--
create temp table tmptz (f1 timestamptz primary key);
insert into tmptz values ('2017-01-18 00:00+00');
explain (costs off)
select * from tmptz where f1 at time zone 'utc' = '2017-01-18 00:00';
diff --git a/src/test/regress/sql/timestamptz.sql b/src/test/regress/sql/timestamptz.sql
index 69b36d0420..11d9f05b64 100644
--- a/src/test/regress/sql/timestamptz.sql
+++ b/src/test/regress/sql/timestamptz.sql
@@ -607,14 +607,35 @@ SELECT '2011-03-27 00:00:00 UTC'::timestamptz AT TIME ZONE 'MSK';
SELECT '2014-10-25 21:00:00 UTC'::timestamptz AT TIME ZONE 'MSK';
SELECT '2014-10-25 21:59:59 UTC'::timestamptz AT TIME ZONE 'MSK';
SELECT '2014-10-25 22:00:00 UTC'::timestamptz AT TIME ZONE 'MSK';
SELECT '2014-10-25 22:00:01 UTC'::timestamptz AT TIME ZONE 'MSK';
SELECT '2014-10-25 23:00:00 UTC'::timestamptz AT TIME ZONE 'MSK';
+--
+-- Test LOCAL time zone
+--
+BEGIN;
+SET LOCAL TIME ZONE 'Europe/Paris';
+VALUES (CAST('1978-07-07 19:38 America/New_York' AS TIMESTAMP WITH TIME ZONE) AT LOCAL);
+VALUES (TIMESTAMP '1978-07-07 19:38' AT LOCAL);
+SET LOCAL TIME ZONE 'Australia/Sydney';
+VALUES (CAST('1978-07-07 19:38 America/New_York' AS TIMESTAMP WITH TIME ZONE) AT LOCAL);
+VALUES (TIMESTAMP '1978-07-07 19:38' AT LOCAL);
+RESET TIME ZONE;
+CREATE VIEW local_time_zone AS
+ VALUES (CAST('1978-07-07 19:38 America/New_York' AS TIMESTAMP WITH TIME ZONE) AT LOCAL,
+ CAST('1978-07-07 19:38 America/New_York' AS TIMESTAMP WITH TIME ZONE) AT TIME ZONE current_setting('TimeZone'),
+ TIMESTAMP '1978-07-07 19:38' AT LOCAL,
+ TIMESTAMP '1978-07-07 19:38' AT TIME ZONE current_setting('TimeZone'));
+\sv local_time_zone
+TABLE local_time_zone;
+DROP VIEW local_time_zone;
+COMMIT;
+
--
-- Test that AT TIME ZONE isn't misoptimized when using an index (bug #14504)
--
create temp table tmptz (f1 timestamptz primary key);
insert into tmptz values ('2017-01-18 00:00+00');
explain (costs off)
select * from tmptz where f1 at time zone 'utc' = '2017-01-18 00:00';
base-commit: 3f1aaaa180689f2015e7f7bd01c9be6d7a993b42
--
2.34.1
