Class: Redis::Bloomfilter

Inherits:
Object
  • Object
show all
Defined in:
lib/redis/bloomfilter.rb,
lib/redis/bloomfilter/version.rb

Constant Summary collapse

VERSION = 
"0.0.3"

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(options = {}) ⇒ Bloomfilter

Usage: Redis::Bloomfilter.new :size => 1000, :error_rate => 0.01 It creates a bloomfilter with a capacity of 1000 items and an error rate of 1%

Raises:

  • (ArgumentError) 


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# File 'lib/redis/bloomfilter.rb', line 9

def initialize(options = {})
  @options = {
    :size         => 1000,
    :error_rate   => 0.01,
    :key_name     => 'redis-bloomfilter',
    :hash_engine  => 'md5',
    :redis        => Redis.current,
    :driver       => nil
  }.merge options

  raise ArgumentError, "options[:size] && options[:error_rate] cannot be nil" if options[:error_rate].nil? || options[:size].nil?

  #Size provided, compute hashes and bits

  @options[:size]       = options[:size]
  @options[:error_rate] = options[:error_rate] ? options[:error_rate] : @options[:error_rate]
  @options[:bits]       = Bloomfilter.optimal_m options[:size], @options[:error_rate]
  @options[:hashes]     = Bloomfilter.optimal_k options[:size], @options[:bits]

  @redis = @options[:redis] || Redis.current
  @options[:hash_engine] = options[:hash_engine] if options[:hash_engine]

  if @options[:driver].nil?
    ver = @redis.info['redis_version']

    if Gem::Version.new(ver) >= Gem::Version.new('2.6.0')
      @options[:driver] = 'lua'
    else
      @options[:driver] = 'ruby'
    end
  end

  driver_class = Redis::BloomfilterDriver.const_get(driver_name)
  @driver = driver_class.new @options
  @driver.redis = @redis 
end

Instance Attribute Details

#driver ⇒ Object (readonly)

Returns the value of attribute driver.



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# File 'lib/redis/bloomfilter.rb', line 5

def driver
  @driver
end

#options ⇒ Object (readonly)

Returns the value of attribute options.



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# File 'lib/redis/bloomfilter.rb', line 4

def options
  @options
end

Class Method Details

.optimal_k(num_of_elements, bf_size) ⇒ Object 



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# File 'lib/redis/bloomfilter.rb', line 52

def self.optimal_k num_of_elements, bf_size
  h = (Math.log(2) * (bf_size / num_of_elements)).round
  h+=1 if h == 0
  h
end

.optimal_m(num_of_elements, false_positive_rate = 0.01) ⇒ Object

Methods used to calculate M and K Taken from en.wikipedia.org/wiki/Bloom_filter#Probability_of_false_positives



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# File 'lib/redis/bloomfilter.rb', line 48

def self.optimal_m num_of_elements, false_positive_rate = 0.01
  (-1 * (num_of_elements) * Math.log(false_positive_rate) / (Math.log(2) ** 2)).round
end

.version ⇒ Object 



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# File 'lib/redis/bloomfilter/version.rb', line 4

def self.version
  "redis-bloomfilter version #{VERSION}"
end

Instance Method Details

#clear ⇒ Object

It deletes a bloomfilter



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# File 'lib/redis/bloomfilter.rb', line 73

def clear
  @driver.clear
end

#include?(key) ⇒ Boolean

It checks if a key is part of the set

Returns:

  • (Boolean) 


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# File 'lib/redis/bloomfilter.rb', line 64

def include?(key)
  @driver.include?(key)
end

#insert(data) ⇒ Object

Insert a new element



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# File 'lib/redis/bloomfilter.rb', line 59

def insert(data)
  @driver.insert data
end

#remove(key) ⇒ Object 



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# File 'lib/redis/bloomfilter.rb', line 68

def remove(key)
  @driver.remove key if @driver.respond_to? :remove
end