postgresql - now() 默认值都显示相同的时间戳

Question

我创建了包含一列(类型:带时区的时间戳)的表，并将其默认值设置为 now() (current_timestamp())。

我在单个函数的单独语句中运行了一系列插入，我注意到所有时间戳都等于(毫秒)，函数值是否以某种方式缓存并为整个函数调用或事务共享？

Answer 1

即expected and documented行为:

来自手册:

Since these functions return the start time of the current transaction, their values do not change during the transaction. This is considered a feature: the intent is to allow a single transaction to have a consistent notion of the "current" time, so that multiple modifications within the same transaction bear the same time stamp.

如果你想要在每次运行语句时改变一些东西，你需要使用 statement_timestamp() 甚至 clock_timestamp()(再次参见手册中的描述)