Using localtime would be absurd. Especially since time goes back during summer time change.
I believe our implementation should use UTC. No one forbids us from assuming that our local time for generating uuid is UTC.
Andrey Borodin wrote on 1/18/2024 2:17 PM:
On 17 Jan 2024, at 02:19, Jelte Fennema-Nio <postgres@jeltef.nl> wrote:
I want to ask Kyzer or Brad, I hope they will see this message. I'm working on the patch for time extraction for v1, v6 and v7.
Do I understand correctly, that UUIDs contain local time, not UTC time? For examples in [0] I see that "A.6. Example of a UUIDv7 Value" I see that February 22, 2022 2:22:22.00 PM GMT-05:00 results in unix_ts_ms = 0x017F22E279B0, which is not UTC, but local time.
Is it intentional? Section "5.1. UUID Version 1" states otherwise.
If so, I should swap signatures of functions from TimestampTz to Timestamp.
I'm hard-coding examples from this standard to tests, so I want to be precise...
If I follow the standard I see this in tests:
+-- extract UUID v1, v6 and v7 timestamp
+SELECT uuid_extract_time('C232AB00-9414-11EC-B3C8-9F6BDECED846') at time zone 'GMT-05';
+ timezone
+--------------------------
+ Wed Feb 23 00:22:22 2022
+(1 row)
Current patch version attached. I've addressed all other requests: function renames, aliases, multiple functions instead of optional params, cleaner catalog definitions, not throwing error when [var,ver,time] value is unknown.
What is left: deal with timezones, improve documentation.
Best regards, Andrey Borodin.
[0] https://datatracker.ietf.org/doc/html/draft-ietf-uuidrev-rfc4122bis#name-example-of-a-uuidv1-value
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