pfmerge.3valkey - Man Page

PFMERGE destkey sourcekey [sourcekey...]

Merge multiple HyperLogLog values into a 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).

If the destination variable exists, it is treated as one of the source sets and its cardinality will be included in the cardinality of the computed HyperLogLog.

valkey-protocol(7) Simple string reply: OK.

O(N) to merge N HyperLogLogs, but with high constant times.

@hyperloglog @slow @write

• Available since: 2.8.9

127.0.0.1:6379> PFADD hll1 foo bar zap a
(integer) 1
127.0.0.1:6379> PFADD hll2 a b c foo
(integer) 1
127.0.0.1:6379> PFMERGE hll3 hll1 hll2
OK
127.0.0.1:6379> PFCOUNT hll3
(integer) 6

pfadd(3valkey), pfcount(3valkey), pfdebug(3valkey), pfselftest(3valkey)