ZCOUNT key min max
Available since: 2.0.0
Time complexity: O(log(N)) with N being the number of elements in the sorted set.
ACL categories:
@read
@sortedset
@fast
Returns the number of elements in the sorted set at key with a score between
min and max.
The min and max arguments have the same semantic as described for
ZRANGEBYSCORE.
Note: the command has a complexity of just O(log(N)) because it uses elements ranks (see ZRANK) to get an idea of the range. Because of this there is no need to do a work proportional to the size of the range.
Return
Integer reply: the number of elements in the specified score range.