Cast or extract timestamp from v1 UUID in PostgreSQL

Question

I'm trying to extract the timestamp from a Version 1 UUID, naively wished this worked:

SELECT '3efe0a20-f1b3-11e3-bb44-14109fec739e'::uuid::timestamp;

Here is a quick example showing how to extract the time in Go, but I'm hoping PostgreSQL has something built-in rather than creating a one-off PL/pgSql function:
http://play.golang.org/p/XRCooLgfaG

Answer 1

An alternative to @Krut's implementation that is quite a bit faster based in our testing:

CREATE OR REPLACE FUNCTION uuid_timestamp(uuid UUID) RETURNS TIMESTAMPTZ AS $$
DECLARE
  bytes bytea; 
BEGIN
  bytes := uuid_send(uuid);
  RETURN to_timestamp(
             (
                 (
                   (get_byte(bytes, 0)::bigint << 24) |
                   (get_byte(bytes, 1)::bigint << 16) |
                   (get_byte(bytes, 2)::bigint <<  8) |
                   (get_byte(bytes, 3)::bigint <<  0)
                 ) + (
                   ((get_byte(bytes, 4)::bigint << 8 |
                   get_byte(bytes, 5)::bigint)) << 32
                 ) + (
                   (((get_byte(bytes, 6)::bigint & 15) << 8 | get_byte(bytes, 7)::bigint) & 4095) << 48
                 ) - 122192928000000000
             ) / 10000 / 1000::double precision
         );
END
$$ LANGUAGE plpgsql
IMMUTABLE PARALLEL SAFE
RETURNS NULL ON NULL INPUT;

Note, it will only do millisecond precision so you may want to tweak the function's "/ 10000 / 1000::double precision" bit to just "/ 10000000::double precision" instead.

Example:

=> select uuid_timestamp(uuid_generate_v1()), now();
       uuid_timestamp       |              now
----------------------------+-------------------------------
 2020-04-29 17:40:54.519+00 | 2020-04-29 17:40:54.518204+00
(1 row)

Also, it is assuming the input is a v1. If you attempt to give it something like a v4, expect to get weird answers or alter the function to RAISE if it isn't v1.

=> select uuid_timestamp(uuid_generate_v4());
       uuid_timestamp
----------------------------
 4251-12-19 17:38:34.866+00
(1 row)

Answer 2

I've tested this with uuid's from my database and it seems to work very well, even without the unsigned bigints

CREATE FUNCTION uuid_timestamp(id uuid) RETURNS timestamptz AS $$
  select TIMESTAMP WITH TIME ZONE 'epoch' +
      (((('x' || lpad(split_part(id::text, '-', 1), 16, '0'))::bit(64)::bigint) +
      (('x' || lpad(split_part(id::text, '-', 2), 16, '0'))::bit(64)::bigint << 32) +
      ((('x' || lpad(split_part(id::text, '-', 3), 16, '0'))::bit(64)::bigint&4095) << 48) - 122192928000000000) / 10000000 ) * INTERVAL '1 second';    
$$ LANGUAGE SQL
  IMMUTABLE
  RETURNS NULL ON NULL INPUT;

a V1 uuid I created in the 2099 future!

select uuid_timestamp('6d248400-65b7-1243-a57a-14109fec739e');
uuid_timestamp     
------------------------
 2099-08-01 11:30:00-07
(1 row)