Postgres maximum value for BIGINT

Question

Is it possible to get the maximum value for BIGINT type without hardcoding it?

I know that the limit is well known, however I wouldn't like to hardcode it.

Answer 1

Just for fun: Building on alexpods' answer, we could define a "generic" function (assuming two's complement) for all postgres integers:

create or replace function
  minint(a anyelement)
  returns anyelement
  immutable
  language sql
as $$
  select ((a - a) - 1) << (8 * pg_column_size(a) - 1);
$$
;

create or replace
  function maxint(a anyelement)
  returns anyelement
  immutable
  language sql
as $$
  select ~minint(a)
$$
;

Usage:

select
  minint(0::smallint)
  , maxint(0::smallint)
  , minint(0::int)
  , maxint(0::int)
  , minint(0::bigint)
  , maxint(0::bigint)
;

Result:

 minint | maxint |   minint    |   maxint   |        minint        |       maxint        
--------+--------+-------------+------------+----------------------+---------------------
 -32768 |  32767 | -2147483648 | 2147483647 | -9223372036854775808 | 9223372036854775807
(1 row)