PFMERGE

The PFMERGE command merges multiple HyperLogLog values into a single destination key.

The resulting HyperLogLog approximates the cardinality of the union of all source HyperLogLogs.

Syntax

PFMERGE destkey [sourcekey [sourcekey ...]]

Parameters

• destkey - Destination HyperLogLog key
• sourcekey - One or more source HyperLogLog keys

Return

Simple string reply: OK.

Notes

• If destkey does not exist, it will be created as an empty HyperLogLog.
• If a sourcekey does not exist, it is treated as an empty HyperLogLog (ignored).

Examples

redis> PFADD hll1 element1 element2 element3 element4 element5
(integer) 1
redis> PFADD hll2 a b c d
(integer) 1
redis> PFMERGE hll_dest hll1 hll2
OK
redis> PFCOUNT hll_dest
(integer) 9