Execution example::

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