1 unstable release
0.5.0 | Jun 17, 2024 |
---|
#1106 in Data structures
101 downloads per month
21KB
337 lines
bugu
An implementation of Cuckoo filter in Rust.
Cuckoo filter is a Bloom filter replacement for approximated set-membership queries. While Bloom filters are well-known space-efficient data structures to serve queries like "if item x is in a set?", they do not support deletion. Their variances to enable deletion (like counting Bloom filters) usually require much more space.
Cuckoo filters provide the flexibility to add and remove items dynamically. A cuckoo filter is based on cuckoo hashing (and therefore named as cuckoo filter). It is essentially a cuckoo hash table storing each key's fingerprint. Cuckoo hash tables can be highly compact, thus a cuckoo filter could use less space than conventional Bloom filters, for applications that require low false positive rates (< 3%).
For details about the algorithm and citations please use this article for now
"Cuckoo Filter: Better Than Bloom" by Bin Fan, Dave Andersen and Michael Kaminsky
Example usage
use bugu::CuckooFilter;
let value: &str = "hello world";
// Create cuckoo filter with default max capacity of 1000000 items
let mut cf = CuckooFilter::new();
// Add data to the filter
let success = cf.add(value).unwrap();
// success ==> Ok(())
// Lookup if data is in the filter
let success = cf.contains(value);
// success ==> true
// Test and add to the filter (if data does not exists then add)
let success = cf.test_and_add(value).unwrap();
// success ==> Ok(false)
// Remove data from the filter.
let success = cf.delete(value);
// success ==> true
Notes & TODOs
- This implementation uses a a static bucket size of 4 fingerprints and a fingerprint size of 1 byte based on my understanding of an optimal bucket/fingerprint/size ratio from the aforementioned paper.
- When the filter returns
NotEnoughSpace
, the element given is actually added to the filter, but some random other element gets removed. This could be improved by implementing a single-item eviction cache for that removed item.
Dependencies
~0.3–1MB
~11K SLoC