PostgreSQL PL/pgSQL NUMERIC to BIT VARYING

numeric_to_bit.pgsql

-- source: https://stackoverflow.com/a/50119025

create function numeric_to_bit(numeric) returns bit varying
    language plpgsql
as
$$
DECLARE
  num ALIAS FOR $1;
  -- 1 + largest positive BIGINT --
  max_bigint NUMERIC := '9223372036854775808' :: NUMERIC(19, 0);
  result BIT VARYING;
BEGIN
  WITH
      chunks (exponent, chunk) AS (
        SELECT
          exponent,
          floor((num / (max_bigint ^ exponent) :: NUMERIC(300, 20)) % max_bigint) :: BIGINT
        FROM generate_series(0, 5) exponent
    )
  SELECT bit_or(chunk :: BIT(300) :: BIT VARYING << (63 * (exponent))) :: BIT VARYING
  FROM chunks INTO result;
  RETURN result;
END;
$$;

alter function numeric_to_bit(numeric) owner to postgres;