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Re:Bloom Filters: More than a space-efficient hashmap by thomasmg on Wednesday August 11, 2021 @03:38AM (#28139161)
Yes exactly. Do a bitwise AND / OR, and count the number of bits that are set. From this count, you can estimate the number of entries in the set: https://en.wikipedia.org/wiki/Bloom_filter#Approximating_the...

HyperLogLog (and variants) can do the union part as well, and need much less space than Bloom filters thought. For large sets, that is. For cardinality smaller than e.g. 100, Bloom filters are better.

Re:Bloom Filters: More than a space-efficient hashmap by fnord77 on Wednesday August 11, 2021 @07:02PM (#28149131)
yes!

Also another alternative is Theta datasketches.