PostgreSQL timestamp踩坑记录与填坑指南

项目Timezone情况

NodeJS：UTC+08

PostgreSQL：UTC+00

timestampTest.js
const { Client } = require('pg')
const client = new Client()
 
client.connect()
let sql = ``
client.query(sql, (err, res) => {
 console.log(err ? err.stack : res.rows[0].datetime)
 client.end()
})

不同时区to_timestamp查询结果

测试输入数据为1514736000(UTC时间2017-12-31 16:00:00,北京时间2018-01-01 00:00:00)

1、timezone=UTC

BEGIN;
SET TIME ZONE 'UTC';
SELECT to_timestamp(1514736000) as datetime;
END;

直接查询：2017-12-31 16:00:00+00YES

pg查询:2017-12-31T16:00:00.000ZYES

2、timezone=PRC

BEGIN;
SET TIME ZONE 'PRC';
SELECT to_timestamp(1514736000) as datetime;
END;

直接查询：2018-01-01 00:00:00+08NO

pg查询:2017-12-31T16:00:00.000ZYES

PostgreSQL官方文档对timestamp的一个描述

详见：8.5.1.3. Time Stamps

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.

坑

使用to_timestamp进行时间转换且DB时区非UTC时，写入**timestamp without time zone**类型的COLUMN则会与预期结果不符。

不同Timezone/columnType查询结果

1、timezone=UTC,timestamp with timezone

BEGIN;
SET TIME ZONE 'UTC';
SELECT TIMESTAMP WITH TIME ZONE '2017-12-31T16:00:00+00' as datetime;
END;

直接查询：2017-12-31 16:00:00+00YES

pg查询:2017-12-31T16:00:00.000ZYES

2、timezone=UTC,timestamp without timezone

BEGIN;
SET TIME ZONE 'UTC';
SELECT TIMESTAMP '2017-12-31T16:00:00+00' as datetime;
END;

直接查询：2017-12-31 16:00:00YES

pg查询:2017-12-31T08:00:00.000ZNO

3、timezone=PRC,timestamp with timezone

BEGIN;
SET TIME ZONE 'PRC';
SELECT TIMESTAMP WITH TIME ZONE '2017-12-31T16:00:00+00' as datetime;
END;

直接查询：2018-01-01 00:00:00+08YES

pg查询:2017-12-31T16:00:00.000ZYES

4、timezone=PRC,timestamp without timezone

BEGIN;
SET TIME ZONE 'PRC';
SELECT TIMESTAMP '2017-12-31T16:00:00+00' as datetime;
END;

直接查询：2017-12-31 16:00:00YES

pg查询:2017-12-31T08:00:00.000ZNO

据以上结果可判定：

使用pg查询**timestamp without time zone**类型的COLUMN时，会将数据库存储的时间当做北京时间而非UTC时间，与数据库时区没有关系。

总结

网上类似问题的解决办法是将DB时区改为UTC+08。

原理：写入DB的时间实际为北京时间，pg库恰好是当做北京时间读取，所以时间戳就不会出问题了。

假如应用部署在不同的地域，使用timestamp without time zone存储timestamp这样的设计简直是灾难。

不要用timestamp without time zone存储timestamp!

不要用timestamp without time zone存储timestamp!

不要用timestamp without time zone存储timestamp!

补充：pg查询时间间隔（timestamp类型）

create_date timestamp(6) without time zone

1.从2015-10-12到2015-10-13 之间的4点到9点的数据

select * from schedule where create_date 
between to_date('2015-10-12','yyyy-MM-dd') 
and to_date('2015-10-13','yyyy-MM-dd')
and EXTRACT(hour from create_date) between 4 and 9;

结果：

2.2015-10-12五点的数据

select * from schedule where hospital_id='syzyyadmin' and date_trunc('hour',create_date)=to_timestamp('2015-10-12 05','YYYY-MM-DD HH24')

结果：