Execution example::

  select --table Comments --query posted_by:bob --output_columns comment --drilldown hash_tags
  # [
  #   [
  #     0, 
  #     1337566253.89858, 
  #     0.000355720520019531
  #   ], 
  #   [
  #     [
  #       [
  #         4
  #       ], 
  #       [
  #         [
  #           "comment", 
  #           "ShortText"
  #         ]
  #       ], 
  #       [
  #         "First post. test,test..."
  #       ], 
  #       [
  #         "@alice Thanks!"
  #       ], 
  #       [
  #         "I've just used 'Try-Groonga' now! #groonga"
  #       ], 
  #       [
  #         "I'm come at city of New York for development camp! #groonga #travel"
  #       ]
  #     ], 
  #     [
  #       [
  #         2
  #       ], 
  #       [
  #         [
  #           "_key", 
  #           "ShortText"
  #         ], 
  #         [
  #           "_nsubrecs", 
  #           "Int32"
  #         ]
  #       ], 
  #       [
  #         "groonga", 
  #         2
  #       ], 
  #       [
  #         "travel", 
  #         1
  #       ]
  #     ]
  #   ]
  # ]
