Pseudo unique ID generator using a combination of memory addresses, time and random number generators. IDs are unique at worst unique 55% of the time, and at best up to 95% of the time.

generatePseudoUniqueId.lua

MAX_ID_LENGTH = 10

local generatePseudoUniqueId = function()
    local threadAddress = tostring({}):sub(10)

    local threadAddressLetters = threadAddress:gsub("%d", "")
    local threadAddressNumbers = threadAddress:gsub("[a-z]", "")

    local threadAddressNumber = tonumber(threadAddressNumbers)
    local maxNumberWidth = MAX_ID_LENGTH - threadAddressLetters:len()
    local maxRandomNumber = tonumber(string.rep("9", maxNumberWidth))

    math.randomseed(os.time() + threadAddressNumber)

    local randomNumber = math.random(maxRandomNumber)
    local idFormatString = string.format( "%s%d%s", "%s%0", maxNumberWidth, "d")

    return string.format(idFormatString, threadAddressLetters, randomNumber)
end

return generatePseudoUniqueId

test.lua

local generatePseudoUniqueId = require "generatePseudoUniqueId"

local uniqueIdCounts = {}
local minUniqueIdCount = 9999999
local maxUniqueIdCount = 0

for i=0, 1000 do
    local ids = {}

    for i=0, 10000 do
        table.insert(ids, generatePseudoUniqueId())
    end

    local uniqueIdCount = 0
    local uniqueIds = {}

    for _, id in ipairs(ids) do
        if not uniqueIds[id] then
            uniqueIdCount = uniqueIdCount + 1
        end

        uniqueIds[id] = true
    end


    io.write(string.format("%d\t", uniqueIdCount))

    table.insert(uniqueIdCounts, uniqueIdCount)

    if uniqueIdCount < minUniqueIdCount then
        minUniqueIdCount = uniqueIdCount
    end

    if uniqueIdCount > maxUniqueIdCount then
        maxUniqueIdCount = uniqueIdCount
    end
end

print()

local sum = 0

for _, uniqueIdCount in ipairs(uniqueIdCounts) do
    sum = sum + uniqueIdCount
end

print(string.format("10K IDs generated 1000 times: Min unique ID count: %f | Max unique ID count: %f | Average unique ID count: %f", 
    minUniqueIdCount,
    maxUniqueIdCount,
    sum / #uniqueIdCounts))