Execution example::

  select Entries --match_columns content --query 'mroonga OR _key:Groonga' --query_flags NONE
  # [
  #   [
  #     0, 
  #     1337566253.89858, 
  #     0.000355720520019531
  #   ], 
  #   [
  #     [
  #       [
  #         1
  #       ], 
  #       [
  #         [
  #           "_id", 
  #           "UInt32"
  #         ], 
  #         [
  #           "_key", 
  #           "ShortText"
  #         ], 
  #         [
  #           "content", 
  #           "Text"
  #         ], 
  #         [
  #           "n_likes", 
  #           "UInt32"
  #         ], 
  #         [
  #           "tag", 
  #           "ShortText"
  #         ]
  #       ], 
  #       [
  #         3, 
  #         "Mroonga", 
  #         "I also started to use Mroonga. It's also very fast! Really fast!", 
  #         15, 
  #         "Groonga"
  #       ]
  #     ]
  #   ]
  # ]
