Performance of Bit String

Hi,

I tried to store a BitString of length 2 million in a Postgres table (see
code below), but it did not complete even in 3 mins and then I cancelled
it. Surprisingly, it only took few seconds when BitString was of length
500K. Is there any restriction of length of BitString or am I missing
something here?

create table bit_test(
id smallint,
memset bit(200000)
) ;

DECLARE
memset bit varying:= B'0';
BEGIN
--PERFORM memset;
FOR i In 1..2000000 LOOP
memset := (memset || B'1') ; -- (B'1' << i);
END LOOP;

INSERT INTO bit_test VALUES(1,B'1',memset :: bit(2000000));

RETURN bit_length(memset);
END;

Thanks,
Rupendra