Execution example::

  logical_select \
    --logical_table Entries \
    --shard_key created_at \
    --limit 0 \
    --output_columns _id \
    --drilldown tag \
    --drilldown_filter "_nsubrecs > 1" \
    --drilldown_output_columns _key,_nsubrecs
  # [
  #   [
  #     0,
  #     1337566253.89858,
  #     0.000355720520019531
  #   ],
  #   [
  #     [
  #       [
  #         5
  #       ],
  #       [
  #         [
  #           "_id",
  #           "UInt32"
  #         ]
  #       ]
  #     ],
  #     [
  #       [
  #         2
  #       ],
  #       [
  #         [
  #           "_key",
  #           "ShortText"
  #         ],
  #         [
  #           "_nsubrecs",
  #           "Int32"
  #         ]
  #       ],
  #       [
  #         "Groonga",
  #         2
  #       ],
  #       [
  #         "Senna",
  #         2
  #       ]
  #     ]
  #   ]
  # ]
