How to use Redis HyperLogLog

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Redis has the HyperLogLog data structure to store many unique events, and it takes up a constant amount of memory. HyperLogLog is a probabilistic structure which means with a large data set, the count of the number of elements can have an error of up to 0.81%. Redis would consume a huge amount of time to process millions of items and Redis Sets can be used only in small or medium projects. Use Redis HyperLogLog instead. To write data to Redis, use the `pfadd key [element [element...].` command. To read, use pfcount key [key ...] command. Use The pfmerge command to merge several HyperLogLog keys into a single one.