Supported Probabilistic Data Structures
Redis includes a single Probabilistic Data Structure (PDS), the HyperLogLog which is used to count distinct elements in a multiset. RedisBloom adds to redis five additional PDS.
- Bloom Filter - test for membership of elements in a set.
- Cuckoo Filter - test for membership of elements in a set.
- Count-Min Sketch - count the frequency of elements in a stream.
- TopK - maintain a list of most frequent K elements in a stream.
- T-digest Sketch - query for quantile.
Probabilistic Data Structures API
Details on module's commands can be filtered for a specific PDS.
Bloom Filter commands.
Cuckoo Filter commands.
Count-Min Sketch commands.
TopK list commands.
T-digest Sketch commands.
The details also include the syntax for the commands, where:
- Command and subcommand names are in uppercase, for example
- Optional arguments are enclosed in square brackets, for example
- Additional optional arguments, such as multiple element for insertion or query, are indicated by three period characters, for example
Commands usually require a key's name as their first argument and an element to add or to query.
Some commands has complexity
O(k) which indicated the number of hash functions. The number of hash functions is constant and complexity may be considered