Lua Bloom Filter Module

1. Overview

A Bloom filter is a space-efficient probabilistic data structure that is used to test whether an element is a member of a set.

2. Module

2.1. Example Usage

require "bloom_filter"

local bf = bloom_filter.new(1000, 0.01)
local found = bf:query("test")
-- found == false
bf:add("test")
found = bf:query("test")
-- found == true

2.2. Functions

2.2.1. new

require "bloom_filter"
local bf = bloom_filter.new(1000, 0.01)

Import the Lua bloom_filter via the Lua 'require' function. The module is globally registered and returned by the require function.

Arguments

• items (unsigned) The maximum number of items to be inserted into the filter (must be > 1)
• probability (double) The probability of false positives (must be between 0 and 1)

Return

• bloom_filter userdata object.

2.2.2. version

require "bloom_filter"
local v = bloom_filter.version()
-- v == "1.0.0"

Returns a string with the running version of bloom_filter.

Arguments

• none

Return

• Semantic version string

2.3. Methods

2.3.1. add

local added = bf:add(key)

Adds an item to the bloom filter.

Arguments

• key (string/number) The key to add in the bloom filter.

Return

• True if the key was added, false if it already existed.

2.3.2. query

local found = bf:query(key)

Checks for the existence of the key in the bloom filter.

Arguments

• key (string/number) The key to lookup in the bloom filter.

Return

• True if the key exists, false if it doesn't.

2.3.3. count

local added = bf:count()

Returns the number of items in the bloom.

Arguments

• none

Return

• Returns the number of distinct items added to the set.

2.3.4. clear

bf:clear()

Resets the bloom filter to an empty set.

Arguments

• none

Return

• none