Question 1006

Taking Keys Back Out

Your dataset churns constantly, so the membership guard has to support removal. Which statements about deletion-capable filters are correct?

A

Deleting from a cuckoo filter is only safe for keys that were actually inserted, since a matching fingerprint may belong to a different key

B

A counting Bloom filter uses about the same memory as a plain Bloom filter of equal capacity, since the counters replace the bits one for one

C

A counting Bloom filter replaces each bit with a small counter, so a key is removed by decrementing each of its k counters by one

D

A cuckoo filter deletes a key by clearing that key's fingerprint from whichever of its two candidate buckets currently holds it

E

A plain Bloom filter supports deletion as long as the k bits are cleared in the reverse of the order in which they were originally set