pgSQL time-based sequential UUID generator based on https://www.2ndquadrant.com/en/blog/sequential-uuid-generators/

generate_sequential_uuid.sql

CREATE OR REPLACE FUNCTION generate_sequential_uuid(p_interval_length int DEFAULT 60)
  RETURNS uuid
  LANGUAGE plpgsql
AS $$
DECLARE
  v_i int;
  v_time bigint;
  v_bytes int[16] = '{}';
  v_hex text[16] = '{}';
BEGIN
  v_time := floor(extract(epoch FROM clock_timestamp()) / p_interval_length);
  v_bytes[1] := v_time >> 8 & 255;
  v_bytes[2] := v_time & 255;

  FOR v_i IN 3..16 LOOP
    v_bytes[v_i] := floor(random() * 256);
  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 $$;