Execution example::

  select --table Comments --filter 'geo_in_circle(location,"127975798x502919856",20000)' --output_columns posted_by.name,comment --drilldown hash_tags,posted_by
  # [
  #   [
  #     0, 
  #     1337566253.89858, 
  #     0.000355720520019531
  #   ], 
  #   [
  #     [
  #       [
  #         4
  #       ], 
  #       [
  #         [
  #           "posted_by.name", 
  #           "ShortText"
  #         ], 
  #         [
  #           "comment", 
  #           "ShortText"
  #         ]
  #       ], 
  #       [
  #         "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"
  #       ], 
  #       [
  #         "グニャラくん", 
  #         "groongaなう #groonga"
  #       ], 
  #       [
  #         "OffGao", 
  #         "@daijiro @tasukuchan 登録してみましたよー！"
  #       ], 
  #       [
  #         "OffGao", 
  #         "中野ブロードウェイなうなう"
  #       ]
  #     ], 
  #     [
  #       [
  #         2
  #       ], 
  #       [
  #         [
  #           "_key", 
  #           "ShortText"
  #         ], 
  #         [
  #           "_nsubrecs", 
  #           "Int32"
  #         ]
  #       ], 
  #       [
  #         "groonga", 
  #         2
  #       ], 
  #       [
  #         "travel", 
  #         1
  #       ]
  #     ], 
  #     [
  #       [
  #         2
  #       ], 
  #       [
  #         [
  #           "_key", 
  #           "ShortText"
  #         ], 
  #         [
  #           "_nsubrecs", 
  #           "Int32"
  #         ]
  #       ], 
  #       [
  #         "tasukuchan", 
  #         2
  #       ], 
  #       [
  #         "OffGao", 
  #         2
  #       ]
  #     ]
  #   ]
  # ]
