class Redis::Distributed

def pfmerge(dest_key, *source_key)

the observed Sets of the source HyperLogLog structures.
Merge multiple HyperLogLog values into an unique value that will approximate the cardinality of the union of 
def pfmerge(dest_key, *source_key)
  ensure_same_node(:pfmerge, [dest_key, *source_key]) do |node|
    node.pfmerge(dest_key, *source_key)
  end
end