PL/PGSQL Function for uuid_time_nextval

uuid_time_nextval.sql

CREATE FUNCTION uuid_time_nextval(interval_length int default 60, interval_count int default 65536)
  RETURNS uuid
  LANGUAGE plpgsql
AS $$
DECLARE
  v_i int;
  v_prefix_bytes int = 0;
  v_time bigint;
  v_bytes int[16] = '{}';
  v_hex text[16] = '{}';
BEGIN
	IF interval_length < 1
	THEN 
		RAISE EXCEPTION 'length of interval must be a positive integer';
	END IF;
	
	IF interval_count < 1
	THEN 
		RAISE EXCEPTION 'number of intervals must be a positive integer';
	END IF;
	
	v_time := floor(extract(epoch FROM clock_timestamp()) / interval_length);
	

	v_i := interval_count;
	WHILE v_i > 1 LOOP
		v_i := v_i / 256;
		v_prefix_bytes := v_prefix_bytes + 1;
	END LOOP;
	
	v_i := 1;
	WHILE v_i <= v_prefix_bytes LOOP
		v_bytes[v_i] := v_time >> (8 * (v_prefix_bytes - v_i)) & 255;
		v_i := v_i + 1;
	END LOOP;

	WHILE v_i <= 16 LOOP
		v_bytes[v_i] := floor(random() * 256);
		v_i := v_i + 1;
	END LOOP;								   

	FOR v_i IN 1..16 LOOP
		v_hex[v_i] := lpad(to_hex(v_bytes[v_i]), 2, '0');
	END LOOP;
								   
  RETURN array_to_string(v_hex, '');
END $$;