Redis recently released their new data structure called the HyperLogLog. It allows us to keep a count of unique objects and only takes up a size of 12k bytes. What I don't understand is that Redis's PFCOUNT command is said to be technically a write command. Why is this the case?
Note: as a side effect of calling this function, it is possible that the HyperLogLog is modified, since the last 8 bytes encode the latest computed cardinality for caching purposes. So PFCOUNT is technically a write command.