Execution example::

  select Users --output_columns name,memo,_score --filter 'query("memo * 10", "groonga") || query("memo * 20", "mroonga") || query("memo * 1", "user")' --sort_keys -_score
  # [
  #   [
  #     0, 
  #     1337566253.89858, 
  #     0.000355720520019531
  #   ], 
  #   [
  #     [
  #       [
  #         5
  #       ], 
  #       [
  #         [
  #           "name", 
  #           "ShortText"
  #         ], 
  #         [
  #           "memo", 
  #           "ShortText"
  #         ], 
  #         [
  #           "_score", 
  #           "Int32"
  #         ]
  #       ], 
  #       [
  #         "Tobby", 
  #         "groonga and mroonga user. mroonga is ...", 
  #         51
  #       ], 
  #       [
  #         "Alisa", 
  #         "mroonga user", 
  #         21
  #       ], 
  #       [
  #         "Alice", 
  #         "groonga user", 
  #         11
  #       ], 
  #       [
  #         "Tom", 
  #         "nroonga user", 
  #         1
  #       ], 
  #       [
  #         "Bob", 
  #         "rroonga user", 
  #         1
  #       ]
  #     ]
  #   ]
  # ]
