PFMERGE

PFMERGE destkey [sourcekey [sourcekey ...]]

Available since:

2.8.9

Time complexity:

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

ACL categories:

@write, @hyperloglog, @slow,

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.

Return

Simple string reply: The command just returns OK.

Examples

redis> PFADD hll1 foo bar zap a
Failed to fetch
redis> PFADD hll2 a b c foo
Failed to fetch
redis> PFMERGE hll3 hll1 hll2
Failed to fetch
redis> PFCOUNT hll3
Failed to fetch