generate_series 夏令时变化 - 结果因服务器时区而异

Question

当我的 postgres 服务器在 America/New_York 时区，或者我使用 SET SESSION TIME ZONE 'America/New_York'，generate_series 遵守夏令时变化，我可以获得正确的纪元或时间点我要：

postgres=# SET SESSION TIME ZONE 'America/New_York';
SET
postgres=#
postgres=# with seq(ts) as (select * from generate_series('2018-11-03 00:00:00.000 -04:00', '2018-11-06 13:40:39.067 -05:00', '1d'::interval))
postgres-# select ts, extract(epoch from ts) as epoch, ts at time zone 'America/New_York' as eastern
postgres-# from seq;
           ts           |   epoch    |       eastern
------------------------+------------+---------------------
 2018-11-03 00:00:00-04 | 1541217600 | 2018-11-03 00:00:00
 2018-11-04 00:00:00-04 | 1541304000 | 2018-11-04 00:00:00
 2018-11-05 00:00:00-05 | 1541394000 | 2018-11-05 00:00:00
 2018-11-06 00:00:00-05 | 1541480400 | 2018-11-06 00:00:00
(4 rows)

但是当我的服务器在生产中使用 UTC 时，generate_series 不遵守夏令时更改：

postgres=# SET SESSION TIME ZONE 'UTC';
SET
postgres=# with seq(ts) as (select * from generate_series('2018-11-03 00:00:00.000 -04:00', '2018-11-06 13:40:39.067 -05:00', '1d'::interval))
postgres-# select ts, extract(epoch from ts) as epoch, ts at time zone 'America/New_York' as eastern
postgres-# from seq;
           ts           |   epoch    |       eastern
------------------------+------------+---------------------
 2018-11-03 04:00:00+00 | 1541217600 | 2018-11-03 00:00:00
 2018-11-04 04:00:00+00 | 1541304000 | 2018-11-04 00:00:00
 2018-11-05 04:00:00+00 | 1541390400 | 2018-11-04 23:00:00
 2018-11-06 04:00:00+00 | 1541476800 | 2018-11-05 23:00:00
(4 rows)

通知 11/4 和 11/5 未针对 DST 更改进行调整。

有没有办法在查询时不设置会话时区？

使用 postgres 9.6...

Answer 1

会话时区控制如何解释 1 天的间隔，所以我认为您的问题的答案很简单，不是。

Postgres docs解释如下：

When adding an interval value to (or subtracting an interval value from) a timestamp with time zone value, the days component advances or decrements the date of the timestamp with time zone by the indicated number of days. Across daylight saving time changes (when the session time zone is set to a time zone that recognizes DST), this means interval '1 day' does not necessarily equal interval '24 hours'. For example, with the session time zone set to CST7CDT, timestamp with time zone '2005-04-02 12:00-07' + interval '1 day' will produce timestamp with time zone '2005-04-03 12:00-06', while adding interval '24 hours' to the same initial timestamp with time zone produces timestamp with time zone '2005-04-03 13:00-06', as there is a change in daylight saving time at 2005-04-03 02:00 in time zone CST7CDT.

据我所知，除了将其设置为会话时区之外，没有其他机制可以告诉间隔在特定时区中进行解释。换句话说，我认为您会寻找类似 '1 day tz America/New_York'::interval 的内容，但我认为不存在这样的语法。

Answer 2

您可以在连接时为特定用户 (ALTER USER) 或特定数据库 (ALTER DATABASE) 自动设置时区。

我能想到的唯一其他方法是使用函数。

BEGIN;

CREATE FUNCTION f1() RETURNS SETOF timestamptz
AS $$
SELECT generate_series('2018-11-03 00:00:00-04', '2018-11-06 00:00:00-05', interval '1 day');
$$
LANGUAGE sql
SET timezone = 'America/New_York';                                                                                                               

SET timezone = 'UTC';
SELECT generate_series('2018-11-03 00:00:00-04', '2018-11-06 00:00:00-05', interval '1 day');
SELECT * FROM f1();

ROLLBACK;

产生：

    generate_series
------------------------
 2018-11-03 04:00:00+00
 2018-11-04 04:00:00+00
 2018-11-05 04:00:00+00
 2018-11-06 04:00:00+00
(4 rows)

           f1
------------------------
 2018-11-03 04:00:00+00
 2018-11-04 04:00:00+00
 2018-11-05 05:00:00+00
 2018-11-06 05:00:00+00
(4 rows)

Answer 3

您可以尝试在所需时区生成系列，然后再转换为 UTC：

select generate_series('2018-11-03 00:00:00.000', '2018-11-06 13:40:39.067', '1d'::interval)::timestamp at time zone 'America/New_York'

输出：

2018-11-03 04:00:00+00
2018-11-04 04:00:00+00
2018-11-05 05:00:00+00
2018-11-06 05:00:00+00

generate_series 夏令时变化 - 结果因服务器时区而异

generate_series over daylight savings change - varied results depending on server timezone

database

postgresql

timezone

dst

postgresql-9.6