UUID Collision Test

#!/usr/bin/env ruby
require 'securerandom'

CURRENT_NO_DB_RECORDS = 6_146_992
FACTOR = 10
ITERATIONS = CURRENT_NO_DB_RECORDS * FACTOR

def compute_hash_frequency
  hash_counts = { }

  ITERATIONS.times do
    # The resulting size is around 4/3 the number of bytes given.
    hash = SecureRandom.urlsafe_base64(6)
    hash_counts[hash] = hash_counts.fetch(hash, 0) + 1
  end

  hash_counts
end

def check_it(hash_occurences)
  puts "Calculating Collisions..."
  actual_unique_hash_count = hash_occurences.keys.count

  puts "We expected #{ITERATIONS} results and got #{actual_unique_hash_count} unique hashes back."
  puts "Difference?: #{ITERATIONS - actual_unique_hash_count}"
  puts "Passes?: #{ITERATIONS == actual_unique_hash_count}\n\n"

  min, max = hash_occurences.keys.map { |k| k.length }.minmax
  puts "The min length of hash was #{min}, the max #{max}"
end

check_it compute_hash_frequency