Short URL Safe IDs for Postgres

short-url-safe-ids.sql

CREATE OR REPLACE FUNCTION gen_unique_short_id() returns text
    language plpgsql
as $$
DECLARE
    id text;
BEGIN
    id := encode(gen_random_bytes(6), 'base64');
    id := replace(id, '/', '_');
    id := replace(id, '+', '_');
    RETURN id;
END;
$$;

alter function gen_unique_short_id() owner to postgres;

You also might be able to get by with:

encode(gen_random_bytes(6), 'hex');