redis pfmerge命令

PFMERGE destkey sourcekey [sourcekey …]

Merge multiple HyperLogLog values into an unique value that will approximate
the cardinality of the union of the observed Sets of the source HyperLogLog
structures.

The computed merged HyperLogLog is set to the destination variable, which is
created if does not exist (defaulting to an empty HyperLogLog).

*返回值

Simple string reply: The command just returns OK.

*例子

redis>  PFADD hll1 foo bar zap a

(integer) 1

redis>  PFADD hll2 a b c foo

(integer) 1

redis>  PFMERGE hll3 hll1 hll2

"OK"

redis>  PFCOUNT hll3

(integer) 6
redis>