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PFCOUNT

Last updated 
PFCOUNT key [key ...]
Group
HyperLogLog
Complexity
O(1) for one key, O(N) for N keys
Arity
-2 (at least 2 words, counting the command name)
Flags
read-only
Keys
first 1, last final argument, step 1
HotKV Cloud
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On-Premise
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PFCOUNT returns the estimated number of distinct elements added to the HyperLogLog at key. With several keys it returns the estimate for their union, without changing any of them. A missing key counts as an empty HyperLogLog.

With a single key, PFCOUNT can count as a modification of the key: a WATCH on it sees the key as changed.

In a cluster, all keys must hash to the same slot.

Return value

Section titled “Return value”
Case RESP2 RESP3
Always Integer: the estimated distinct count Integer

The errors are those of PFADD: a WRONGTYPE error for a string that is not a HyperLogLog or a key of another type, and INVALIDOBJ for damaged data.

Examples

Section titled “Examples”
127.0.0.1:6379> PFADD day:1 alice bob carol
(integer) 1
127.0.0.1:6379> PFADD day:2 carol dave
(integer) 1
127.0.0.1:6379> PFCOUNT day:1
(integer) 3
127.0.0.1:6379> PFCOUNT day:1 day:2
(integer) 4
127.0.0.1:6379> PFCOUNT missing
(integer) 0

Compatibility

Section titled “Compatibility”

Same as Redis 7 and Valkey 8.

See also

Section titled “See also”

PFADD, PFMERGE