Execution example::

  select \
    --table Entries \
    --columns[n_likes_sum_per_tag].stage initial \
    --columns[n_likes_sum_per_tag].type UInt32 \
    --columns[n_likes_sum_per_tag].value 'window_sum(n_likes)' \
    --columns[n_likes_sum_per_tag].window.group_keys tag \
    --sort_keys _key \
    --output_columns tag,_key,n_likes,n_likes_sum_per_tag
  # [
  #   [
  #     0, 
  #     1337566253.89858, 
  #     0.000355720520019531
  #   ], 
  #   [
  #     [
  #       [
  #         5
  #       ], 
  #       [
  #         [
  #           "tag", 
  #           "ShortText"
  #         ], 
  #         [
  #           "_key", 
  #           "ShortText"
  #         ], 
  #         [
  #           "n_likes", 
  #           "UInt32"
  #         ], 
  #         [
  #           "n_likes_sum_per_tag", 
  #           "UInt32"
  #         ]
  #       ], 
  #       [
  #         "Senna", 
  #         "Good-bye Senna", 
  #         3, 
  #         6
  #       ], 
  #       [
  #         "Senna", 
  #         "Good-bye Tritonn", 
  #         3, 
  #         6
  #       ], 
  #       [
  #         "Groonga", 
  #         "Groonga", 
  #         10, 
  #         25
  #       ], 
  #       [
  #         "Groonga", 
  #         "Mroonga", 
  #         15, 
  #         25
  #       ], 
  #       [
  #         "Hello", 
  #         "The first post!", 
  #         5, 
  #         5
  #       ]
  #     ]
  #   ]
  # ]
