This causes a syntax error at parallel
CREATE AGGREGATE public.first (
sfunc = public.first_agg,
basetype = anyelement,
stype = anyelement,
parallel = safe
);
Maybe because of this? https://www.postgresql-archive.org/reate-parallel-aggregate-td5923553.html
I don't know if there's a syntax change or something and if there is, what the new syntax would be?