Command builders for Redis HyperLogLog probabilistic data structure.
Provides pure functions that build command lists for HyperLogLog operations,
which allow approximate cardinality estimation (counting unique elements) using
a fixed amount of memory regardless of the number of elements. Supports adding
elements (PFADD), estimating cardinality (PFCOUNT), and merging multiple
HyperLogLog keys (PFMERGE). Each function returns a plain list of strings
suitable for passing to Redis.command/2 or Redis.pipeline/2.
These functions contain no connection or networking logic -- they only construct the Redis protocol command as a list.
Examples
Track unique visitors and estimate the total count:
iex> Redis.Commands.HyperLogLog.pfadd("visitors:2026-04-01", ["user:1", "user:2", "user:3"])
["PFADD", "visitors:2026-04-01", "user:1", "user:2", "user:3"]
iex> Redis.Commands.HyperLogLog.pfcount(["visitors:2026-04-01"])
["PFCOUNT", "visitors:2026-04-01"]Merge multiple days into a weekly count:
iex> Redis.Commands.HyperLogLog.pfmerge("visitors:week:14", ["visitors:2026-04-01", "visitors:2026-04-02"])
["PFMERGE", "visitors:week:14", "visitors:2026-04-01", "visitors:2026-04-02"]Summary
Functions
Builds a PFADD command to add elements to a HyperLogLog key.
Builds a PFCOUNT command to estimate the cardinality of one or more HyperLogLog keys.
Builds a PFMERGE command to merge multiple HyperLogLog keys into a destination key.
Functions
Builds a PFADD command to add elements to a HyperLogLog key.
Redis returns 1 if the internal representation was altered (i.e., the estimated cardinality changed), 0 otherwise.
Example
iex> Redis.Commands.HyperLogLog.pfadd("unique_ips", ["10.0.0.1", "10.0.0.2"])
["PFADD", "unique_ips", "10.0.0.1", "10.0.0.2"]Builds a PFCOUNT command to estimate the cardinality of one or more HyperLogLog keys.
When given multiple keys, Redis returns the approximate cardinality of the union of all the keys without modifying them.
Example
iex> Redis.Commands.HyperLogLog.pfcount(["unique_ips"])
["PFCOUNT", "unique_ips"]Builds a PFMERGE command to merge multiple HyperLogLog keys into a destination key.
The resulting key will contain the union of all source keys. This is useful for computing aggregate cardinality over time periods or shards.
Example
iex> Redis.Commands.HyperLogLog.pfmerge("all_ips", ["ips:shard1", "ips:shard2"])
["PFMERGE", "all_ips", "ips:shard1", "ips:shard2"]