insert record with random field

postgres.sql

insert into cups(reg_id, code, is_enabled, created_at, updated_at ) 
select 
  1  as reg_id, 
  UPPER(substr(md5(''||now()::text||random()::text), 1,8)) as code,
  true as is_enabled,
  to_date(now()::text,
  'YYYY-MM-DD HH24:MI:SS') as created_at,
  to_date(now()::text, 'YYYY-MM-DD HH24:MI:SS') as updated_at
from generate_series(1,4000000) on conflict DO NOTHING;