create or replace function trigger_f() returns trigger as $$
	declare
		old_id integer := null;
		old_name text := null;
		new_id integer := null;
		new_name text := null;
	begin
		if tg_op in('INSERT', 'UPDATE') then
			new_id := new.id;
			new_name := new.name;
		end if;
		if tg_op in('UPDATE', 'DELETE') then
			old_id := old.id;
			old_name := old.name;
		end if;
		insert into log values(
			tg_op,
			old_id,
			old_name,
			new_id,
			new_name,
			current_user,
			current_timestamp
		);
		return new;
	end;
$$ language plpgsql;