Execution example::

  select --table Comments --query hash_tags:@groonga --output_columns posted_by.name,comment --drilldown posted_by
  # [
  #   [
  #     0,
  #     1337566253.89858,
  #     0.000355720520019531
  #   ],
  #   [
  #     [
  #       [
  #         2
  #       ],
  #       [
  #         [
  #           "posted_by.name",
  #           "ShortText"
  #         ],
  #         [
  #           "comment",
  #           "ShortText"
  #         ]
  #       ],
  #       [
  #         "Bob",
  #         "I've just used 'Try-Groonga' now! #groonga"
  #       ],
  #       [
  #         "Bob",
  #         "I'm come at city of New York for development camp! #groonga #travel"
  #       ]
  #     ],
  #     [
  #       [
  #         1
  #       ],
  #       [
  #         [
  #           "_key",
  #           "ShortText"
  #         ],
  #         [
  #           "_nsubrecs",
  #           "Int32"
  #         ]
  #       ],
  #       [
  #         "bob",
  #         2
  #       ]
  #     ]
  #   ]
  # ]
