Question 1521

Merge Without Regret

Your fleet builds sketches per shard and combines them at read time. More than one of these merges is exact, meaning the combined sketch is bit-for-bit what you would have got from feeding the whole stream to a single sketch. Select every merge that is exact.

A

Two Bloom filters of identical size and hash functions, merged with a bitwise OR.

B

Two per-shard top-10 lists, concatenated and re-sorted by count to get the global top 10.

C

Two HyperLogLogs with the same mm, merged by taking the per-register maximum.

D

Two count-min sketches with identical width, depth and hash functions, merged by adding cells position by position.

E

Two HyperLogLogs intersected by taking the per-register minimum, to get the size of the overlap.