Execution example::

  logical_select --logical_table Entries --shard_key created_at
  # [
  #   [
  #     0,
  #     1337566253.89858,
  #     0.000355720520019531
  #   ],
  #   [
  #     [
  #       [
  #         5
  #       ],
  #       [
  #         [
  #           "_id",
  #           "UInt32"
  #         ],
  #         [
  #           "_key",
  #           "ShortText"
  #         ],
  #         [
  #           "content",
  #           "Text"
  #         ],
  #         [
  #           "created_at",
  #           "Time"
  #         ],
  #         [
  #           "n_likes",
  #           "UInt32"
  #         ],
  #         [
  #           "tag",
  #           "ShortText"
  #         ]
  #       ],
  #       [
  #         1,
  #         "The first post!",
  #         "Welcome! This is my first post!",
  #         1436281200.0,
  #         5,
  #         "Hello"
  #       ],
  #       [
  #         2,
  #         "Groonga",
  #         "I started to use Groonga. It's very fast!",
  #         1436284800.0,
  #         10,
  #         "Groonga"
  #       ],
  #       [
  #         3,
  #         "Mroonga",
  #         "I also started to use Mroonga. It's also very fast! Really fast!",
  #         1436288400.0,
  #         15,
  #         "Groonga"
  #       ],
  #       [
  #         1,
  #         "Good-bye Senna",
  #         "I migrated all Senna system!",
  #         1436367600.0,
  #         3,
  #         "Senna"
  #       ],
  #       [
  #         2,
  #         "Good-bye Tritonn",
  #         "I also migrated all Tritonn system!",
  #         1436371200.0,
  #         3,
  #         "Senna"
  #       ]
  #     ]
  #   ]
  # ]
