実行例 ::

  > select --table Comments --query hash_tags:@groonga --output_columns posted_by.name,comment --drilldown posted_by
  [[0,1280378874.22658,0.000485],[[[2],[["posted_by.name","ShortText"],["comment","ShortText"]],["グニャラくん","groongaなう #groonga"],["グニャラくん","groonga開発合宿のため羽田空港に来ました！ #groonga #travel"]],[[1],[["_key","ShortText"],["_nsubrecs","Int32"]],["tasukuchan",2]]]]
  