Execution example::

  plugin_register functions/string
  # [[0,1337566253.89858,0.000355720520019531],true]
  logical_count \
    --logical_table Entries \
    --shard_key created_at \
    --columns[content_length].stage initial \
    --columns[content_length].type UInt32 \
    --columns[content_length].value 'string_length(content)' \
    --filter 'content_length >= 40'
  # [[0,1337566253.89858,0.000355720520019531],2]
