PFMERGE

{{< note >}} This command's behavior varies in clustered Redis environments. See the [multi-key operations]({{< relref "/develop/using-commands/multi-key-operations" >}}) page for more information. {{< /note >}}

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.

Examples

{{% redis-cli %}} PFADD hll1 foo bar zap a PFADD hll2 a b c foo PFMERGE hll3 hll1 hll2 PFCOUNT hll3 {{% /redis-cli %}}

Redis Software and Redis Cloud compatibility

| Redis Software | Redis Cloud | <span style="min-width: 9em; display: table-cell">Notes</span> | |:----------------------|:-----------------|:------| | <span title="Supported">✅ Standard</span> <span title="Supported"><nobr>✅ Active-Active</nobr></span> | <span title="Supported">✅ Standard</span> <span title="Supported"><nobr>✅ Active-Active</nobr></span> | |

Return information

{{< multitabs id="pfmerge-return-info" tab1="RESP2" tab2="RESP3" >}}

Simple string reply: OK.

-tab-sep-

Simple string reply: OK.

{{< /multitabs >}}