Redis-HyperLogLog

http://content.research.neustar.biz/blog/hll.html

案例

# 往hyperloglog对象添加元素
127.0.0.1:6379> PFADD HLL1 Joe Mary King
(integer) 1
# 计算唯一元素个数
127.0.0.1:6379> PFCOUNT HLL1
(integer) 3
# 添加重复元素
127.0.0.1:6379> PFADD HLL1 King
(integer) 0
127.0.0.1:6379> PFCOUNT HLL1
(integer) 3
127.0.0.1:6379> PFADD HLL2 Mark Yur Jack King Joe
(integer) 1
127.0.0.1:6379> PFMERGE HLL HLL1 HLL2
OK
127.0.0.1:6379> PFCOUNT HLL
(integer) 6