On 19.03.24 10:38, Aleksander Alekseev wrote:
Considering the number of environments PostgreSQL can run in (OS +
hardware + virtualization technologies) and the fact that
hardware/software changes I doubt that it's realistic to expect any
particular guarantees from gettimeofday() in the general case.
If we want to be robust without any guarantees from gettimeofday(), then
arguably gettimeofday() is not the right underlying function to use for
UUIDv7. I'm not arguing that, I think we can assume some reasonable
baseline for what gettimeofday() produces. But it would be good to get
some information about what that might be.
Btw., here is util-linux saying
/* Assume that the gettimeofday() has microsecond granularity */
https://github.com/util-linux/util-linux/blob/master/libuuid/src/gen_uuid.c#L232
