PostgreSQL 역할이 아직 존재하지 않는 경우 안전하게 생성하는 방법은 무엇입니까?

DO
$do$
BEGIN
   IF EXISTS (
      SELECT FROM pg_catalog.pg_roles
      WHERE  rolname = 'my_user') THEN

      RAISE NOTICE 'Role "my_user" already exists. Skipping.';
   ELSE
      CREATE ROLE my_user LOGIN PASSWORD 'my_password';
   END IF;
END
$do$;

DO
$do$
BEGIN
   IF EXISTS (
      SELECT FROM pg_catalog.pg_roles
      WHERE  rolname = 'my_user') THEN

      RAISE NOTICE 'Role "my_user" already exists. Skipping.';
   ELSE
      BEGIN   -- nested block
         CREATE ROLE my_user LOGIN PASSWORD 'my_password';
      EXCEPTION
         WHEN duplicate_object THEN
            RAISE NOTICE 'Role "my_user" was just created by a concurrent transaction. Skipping.';
      END;
   END IF;
END
$do$;