HyperLogLog[1] — approximately count distinct elements from an extremely large set (e.g. 10⁹ elements) super efficiently. → Distinct count time complexity[2]:

HyperLogLog[1] — approximately count distinct elements from an extremely large set (e.g. 10⁹ elements) super efficiently. → Distinct count time complexity[2]: O(1) See Redis's PFCOUNT[4]. [1] https://en.wikipedia.org/wiki/HyperLogLog https://en.wikipedia.org/wiki/HyperLogLog [2] For a fixed number of registers (e.g. Redis's implementation) [3] https://redis.io/commands/pfcount/ https://redis.io/commands/pfcount/