SELECT nspname || '.' || C.relname AS "relation",
    pg_size_pretty(pg_relation_size(C.oid)) AS "size",
    T.relname AS "toastrel"
  FROM pg_class C
  LEFT JOIN pg_namespace N ON (N.oid = C.relnamespace)
  LEFT JOIN pg_class T ON (T.reltoastrelid=C.oid)
  WHERE nspname NOT IN ('pg_catalog', 'information_schema')
  ORDER BY pg_relation_size(C.oid) DESC
  LIMIT 20;