Redis HyperLogLog

Redis HYPERLOGLOG Command

Redis HyperLogLog is a algorithm that use randomization in order to provide an approximation of the number of unique elements in a set using just a constant, and small, amount of memory.

HyperLogLog provides a very good approximation of the cardinality of a set even using a very small amount of memory around 12 kbytes per key with a standard error of 0.81% and there is no limit to the number of items you can count, unless you approach 264 items.

Example:

Following example explains how redis HyperLogLog works:

redis 127.0.0.1:6379> PFADD tutorials "redis"

1) (integer) 1

redis 127.0.0.1:6379> PFADD tutorials "mongodb"

1) (integer) 1

redis 127.0.0.1:6379> PFADD tutorials "mysql"

1) (integer) 1

redis 127.0.0.1:6379> PFCOUNT tutorials

(integer) 3

Redis HyperLogLog commands

Below given table shows some basic commands related to redis HyperLogLog: