gistfile1.txt

CREATE OR REPLACE FUNCTION hex2dec(text)
RETURNS bigint LANGUAGE SQL AS
$$
SELECT sum(digit * 16 ^ (length($1)-pos)) ::bigint
FROM (SELECT case
when digit between '0' and '9' then ascii(digit) - 48
when digit between 'A' and 'F' then ascii(digit) - 55
end,
pos as i
FROM (SELECT substring(c from x for 1), x
FROM (values(upper($1))) as a(c),
generate_series(1,length($1)) as t(x))
as u(digit, pos)
) as v(digit, pos);