Amazon Redshift/PostgreSQLのCASE式による効率的なGROUP

これは、2つの集計で行います。

select type, (case when cnt > XXX then url end) as url, sum(cnt) as visit_cnt
from (select type, url, count(*) as cnt
      from t
      group by type, url
     ) t
group by type, (case when cnt > XXX then url end)
order by type, sum(cnt) desc;