Re: Sequence vs UUID

On Wed, Feb 8, 2023 at 4:18 AM veem v <veema0000(at)gmail(dot)com> wrote:

> Thank you So much all for such valuable feedback.
> ..
> So wanted to know from experts here, is there really exists any scenario
> in which UUID really cant be avoided?
>
> Funny you are asking about this. My recent experience is that UUIDs
really get crushed on performance in medium (> 5 million rows) tables.
I found an article by Dave Allie on ULID, and I modified his implementation
to create a timestamp(6) (microsecond level) sequenced version.

Doing an article on this soon. But WITHOUT calling the "gen_random_bytes"
I can generate 2 timestamps at the same microsecond level.
Once that call is included in the function, I've never been close to
returning 2 timestamps at the same microsecond level. Although I did not
run this on multiple threads. This fit our needs for an efficient UUID
formatted key...

9 Bytes (18 Hex Digits) of Randomness at the far right.

Oh, and some time after the year 10,000 you will get some wrap around...
But I expect 256 bit UUIDs will take over before then.

CREATE FUNCTION generate_ulid() RETURNS uuid
LANGUAGE sql
RETURN ((lpad(to_hex((floor((EXTRACT(epoch FROM clock_timestamp()) *
(1000000)::numeric)))::bigint), 14, '0'::text)

|| encode(gen_random_bytes(9), 'hex'::text)))::uuid;