Postgres 12

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select version();

version

PostgreSQL 12.17 on x86_64-pc-linux-gnu, compiled by gcc (GCC) 8.5.0 20210514 (Red Hat 8.5.0-20), 64-bit

SELECT 1

create domain ksuid character varying(27);

create or replace function generate_ksuid()
 returns  ksuid
 language sql 
as $$
    select substring(
             replace(to_char(clock_timestamp(),'yyyymmddhh24missus') 
                     || (to_char(random()*1e9,'000000000')
                    ),' ',''),1,27)::ksuid;
$$; 
 
alter domain ksuid set default generate_ksuid();
 
CREATE DOMAIN

CREATE FUNCTION

ALTER DOMAIN

create table test_ksuid
       ( test_id  ksuid primary key
       , col1     text
       ); 
 
insert into test_ksuid(col1) 
  values ('ABC'), ('Def'), ('yyyyyyy');

CREATE TABLE

INSERT 0 3

select * from test_ksuid;

test_id
col1

202501271732391135308595138
ABC

202501271732391139357561743
Def

202501271732391139675269573
yyyyyyy

SELECT 3

test_id	col1
202501271732391135308595138	ABC
202501271732391139357561743	Def
202501271732391139675269573	yyyyyyy