Postgres Sequence Bulk Increment

example.sql

-- I needed a way to safely pull a bunch of sequence values to my client in order to bulk
-- insert many thousands of rows. I'm doing this because I don't want to use 128-bit keys.
-- I found this:
-- https://www.depesz.com/2008/03/20/getting-multiple-values-from-sequences/

select pg_advisory_lock(123);
alter sequence seq increment by 1000;
select nextval('seq');
alter sequence seq increment by 1;
select pg_advisory_unlock(123);

multi_nextval.sql

-- note that if the sequence's `cache` value is > 1 this will end up
-- setting the sequence value to `nextval + increment * cache`
create or replace function multi_nextval(seqname text, increment int4)
    returns bigint as $$
declare
    seq text;
    lock bigint;
    reply bigint;
begin
    select quote_ident(seqname) into seq;
    select hashtextextended(seqname, 883669774654) into lock;

    perform pg_advisory_lock(lock);
    execute 'alter sequence ' || seq || ' increment by ' || increment::text;
    reply := nextval(seqname);
    execute 'alter sequence ' || seq || ' increment by 1';
    perform pg_advisory_unlock(lock);
    return reply;
end
$$ language 'plpgsql';