efuse_filter

A dependency free Binary Fuse Filter Erlang NIF.

They're faster and smaller than Bloom, Cuckoo, and Xor filters.

This library is almost API compatible with the exor_filter library, and can be used as a replacement without too much hassle.

Table Of Contents

• Benchmarks
• Installation
• Example Usage
  • Basic Usage
  • Elixir Example
  • Incremental Initialization
• Custom Return Values
• Custom Hashing
• Serialization

Benchmarks

This was benchmarked with the exor_benchmark suite that compares several Erlang and Elixir bloom / xor / fuse filter implementations. The full benchmark and results can be found there.

Installation

This library requires Erlang version 24+.

This library is available on hex.pm.

rebar3

%% rebar.config

{deps, [
  %% hex.pm
  {efuse_filter, "0.1.0"},

  %% git
  {efuse_filter, {git, "git://github.com/mpope9/efuse_filter.git", {tag, "0.1.0"}}}
]}.

mix

## mix.exs

defp deps do
  [
    {:efuse_filter, "~> 0.1.0"}
  ]
end

Example Usage

Basic Usage

Filter = fuse8:new(["cat", "dog", "mouse"]),
true = fuse8:contain(Filter, "cat"),
false = fuse8:contain(Filter, "goose").

Elixir Example

alias :fuse8 as: Fuse8

# ...

true =
    [1, 2, 3, 4]
    |> Fuse8.new()
    |> Fuse8.contain(1)

Incremental Initialization

This builds a filter over multiple calls. Filters are immutable. Once finalized, more elements cannot be added.

The exor_filter stores elements using a compressed bitmap. This library uses the optimized Erlang sets version 2 module, and keeps them in Erlang memory. This library will have a higher memory footprint when initializing a filter incrementally compared to the exor_filter.

Filter0 = fuse8:new_empty(),

%% Add multiple elements.
Filter1 = fuse8:add(Filter0, [1, 2]),
Filter2 = fuse8:add(Filter1, [3, 4]),

%% Add single element.
Filter3 = fuse8:add(Filter2, 5),

Filter4 = fuse8:finalize(Filter3),

true = fuse8:contain(Filter4, 1),
false = fuse8:contain(Filter4, 6).

Custom Return Values

fuse8:contain/3 can return a custom value instead of false if the required item isn't present in the filter:

Filter = fuse8:new(["Ricky Bobby", "Cal Naughton Jr."]),
true = fuse8:contain(Filter, "Ricky Bobby", {error, not_found}),
{error, not_found} = fuse8:contain(Filter, "Reese Bobby", {error, not_found}).

Custom Hashing

By default this library uses the erlang:phash2/1 function. If you want to use your own custom hashing, pass none to the fuse8:new/2 function. Values passed to fuse8:/new and fuse8:contain need to be pre-hashed, and those functions will return a {error, pre_hashed_values_should_be_ints} error of non-integer values are passed.

Example usage:

PreHashedList = [...],
Filter = fuse8:new(PreHashedList, none),
true = fuse8:contain(Filter, hd(PreHashedList)).

Using your own hashing method has benefits. If the filter is sent between services other platforms might not have erlang:phash2/1 available. Also for larger filters, a hashing function with a larger key space might be desired. Keys in the C code are mapped to a uint64_t. Keep that in mind when choosing the hashing function.

The exor_filter supports passing a function to do the hashing. This library does not.

Serialization

Filters can be serialized using fuse8:to_bin/1 and fuse8:from_bin/1 and fuse8:from_bin/2.

Functions are provided to the filter in binary form, instead of a nif reference. This can be useful to interop with other platforms / systems. The bin returned can be used with fuse8:contain for ease of use. Example usage:

Example usage:

Filter     = fuse8:new(["test1", "test2", "test3"]),
BinFilter  = fuse8:to_bin(Filter),
true       = fuse8:contain(BinFilter, "test1"),
Filter2    = fuse8:from_bin(BinFilter),
true       = fuse8:contain(Filter2, "test1").

To use custom hashing with a serialized filter, the following fuse8:contain/4 method is provided:

Filter     = fuse8:new(["test1", "test2", "test3"]),
BinFilter  = fuse8:to_bin(Filter),
true       = fuse8:contain(BinFilter, "test1", false, none),
Filter2    = fuse8:from_bin(BinFilter, none),
true       = fuse8:contain(Filter2, "test1").

Build

$ rebar3 compile

Test

$ rebar3 eunit
$ rebar3 cover

Docs

$ rebar3 edoc