Returns the approximated cardinality computed by the HyperLogLog data
structure stored at the specified key.
When called with a single key, returns the approximated cardinality
computed by the HyperLogLog data structure stored at the specified
variable, which is 0 if the variable does not exist.
When called with multiple keys, returns the approximated cardinality
of the union of the HyperLogLogs passed, by internally merging the
HyperLogLogs stored at the provided keys into a temporary HyperLogLog.
Returns the approximated cardinality computed by the HyperLogLog data structure stored at the specified key.
When called with a single key, returns the approximated cardinality computed by the HyperLogLog data structure stored at the specified variable, which is 0 if the variable does not exist.
When called with multiple keys, returns the approximated cardinality of the union of the HyperLogLogs passed, by internally merging the HyperLogLogs stored at the provided keys into a temporary HyperLogLog.