Similarly to sets, sorted sets in Redis support the set operations of union and intersection, although the time complexity of these operations for sorted sets is worse than for sets. Another problem with the sorted set operations is that when using a Redis cluster, union and intersection operations can only be used when the sorted set keys have been sharded to the same hash slot and run on the same node. The
ZINTERSTORE Redis command has a time complexity of
O(nk)+O(mlog(m)), where n is the size of the smallest sorted set; k, the total number of sorted sets being intersected, and m, the number of elements in the resulting final sorted set. Likewise, for the
ZUNIONSTORE command, the time complexity is
O(n)+O(M log(M)) ...