nomon/qf-go

go quotient filter implementation

Quotient Filter

a go implementation of the quotient filter data structure. Quotient filter is a probabilistic data structure similar to a Bloom Filter. As BF it is used to approximate set membership. It never returns false for added keys but has a probability of returning a false positive, the probability depends on the amount of remainder bits and fill rate of the filter.

Its size is 10-20% more than a bloom filter with same FP rate but it usually is faster. It also has a few additional benefits:

• Filters can be merged without rehashing keys
• Adding or checking a key requires evaluating only a single hash function
• Can be resized without rehashing

For more details, see: https://en.wikipedia.org/wiki/Quotient_filter

Interface

// Create a filter that can hold 1m elements while maintaining 1% false positive
// rate when at 1 million items length.
qf := NewProbability(1000000, 0.01)
qf.Add("key")
if !qf.Contains("key") {
  panic("False negative not possible")
}

docs

https://godoc.org/github.com/Nomon/qf-go

Credits

All credit goes to https://github.com/vedantk/quotient-filter this repo is golang port of Vedant Kumars C implementatuon.

License MIT

Additional work Copyright (c) 2016 Matti Savolainen [email protected]
Copyright 2014 Vedant Kumar [email protected]

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software. THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE..

qf-go's Issues

Do not seed

This is library client's responsibility.

Yet better, let New() optionally take rand.Source instance and fall back to global if it's nil.

implement merge

implement iterator

Implement remove

Expose .ContainsHash(uint64)

Expose a Contains() variant that uses client provided hash for efficient lookup over multiple filters.