I know it has been discussed before [1] but one of our customers complained about something weird on one of their multi-tenancy databases (thousands of schemas with a lot of objects inside and one user by schema).
So when I checked the problem is because the missing TOAST for pg_class, and is easy to break it by just:
fabrizio=# create table foo (id int); CREATE TABLE fabrizio=# do $$ begin for i in 1..2500 loop execute 'create user u' || i; execute 'grant all on foo to u' || i; end loop; end; $$; ERROR: row is too big: size 8168, maximum size 8160 CONTEXT: SQL statement "grant all on foo to u2445" PL/pgSQL function inline_code_block line 6 at EXECUTE
Attached patch adds the TOAST to pg_class, and let's open again the discussion around it.
