如何防止 Redshift INSERT 日期时间删除时区？

Question

我有String这种格式的 a:2018-11-01T00:00:00-07:00我想将它转换为 aTIMESTAMP并将其插入到一TIMESTAMP列中。但是，当我插入它时，它会删除-07:00而不先将其转换为-00:00. 如何确保它被正确转换并存储在 Redshift 中？

下面是一个例子： select ORIGINAL_DATE, TO_TIMESTAMP(ORIGINAL_DATE,'YYYY-MM-DD HH24:MI:SS') FROM CDW_LANDING.X where id = XXXXXX;

=> 2018-11-01T00:00:00-07:00 2018-10-31 17:00:00

将TO_TIMESTAMP其转换为2018-10-31 17:00:00这是我想要的。但是，当我插入它时，它会变成2018-11-01 00:00:00并简单地删除-07:00.

这是示例：

insert into cdw_stage.X (ORIG_DT) 
select TO_TIMESTAMP(ORIGINAL_DATE,'YYYY-MM-DD HH24:MI:SS') 
from CDW_LANDING.INVOICE where id = XXXXXX;

但是当我用 查询它时select ORIG_DT from cdw_landing.X;，它显示2018-11-01 00:00:00. 我想看到的是2018-10-31 17:00:00这是什么样TO_TIMESTAMP的功能应该做的。

该ORIG_DT在红移是TIMESTAMP格式。输入日期在VARCHAR.

How do I get Redshift to save this correctly? I also added postgres tag because Redshift is based off of postgres. Thank you so much!!!

Answer 1

2018-11-01T00:00:00-07:00 is not a timestamp (timestamp without time zone) literal, strictly speaking. It is a timestamptz (timestamp with time zone) literal. This is the root of all pain in your question. The wrong cast to timestamp ignores the offset. The Postgres manual:

In a literal that has been determined to be timestamp without time zone, PostgreSQL will silently ignore any time zone indication. That is, the resulting value is derived from the date/time fields in the input value, and is not adjusted for time zone.

Bold emphasis mine.

The use of TO_TIMESTAMP() can't save you. The Redshift manual:

Formats that include a time zone (TZ, tz, or OF) are not supported as input.

(The same is true in Postgres.)

Solution

Cast to timestamptz (or use a column of that type to begin with), the rest should fall in place:

SELECT cast('2018-11-01T00:00:00-07:00' AS timestamptz);

Or:

SELECT '2018-11-01T00:00:00-07:00'::timestamptz;

The manual about casting in Redshift.

When an actual timestamptz is assigned to a timestamp column it is converted according to the current timezone setting of the session automatically. If you want a different target timezone, use the AT TIME ZONE construct. Details:

• Ignoring time zones altogether in Rails and PostgreSQL

The related answer is for Postgres, but timestamp handling in Redshift (while differing in many other aspects!) is the same. The Redshift manual:

将 DATE 或 TIMESTAMP 转换为 TIMESTAMPTZ 时，假定 DATE 或 TIMESTAMP 使用当前会话时区。会话时区默认为 UTC。有关设置会话时区的更多信息，请参阅timezone。