How does HyperLogLog count unique items without storing them?
It hashes every item and examines the distribution of leading zeros in the binary hash output. Since leading zeros are rare (like flipping heads repeatedly), observing many leading zeros statistically implies you've hashed billions of distinct items.
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Count Billions in 12 KilobytesHyperLogLog estimates cardinality by reading leading zeros in hashed values, trading 1% error for fixed memory.
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