Redis HashTable Open Addressing, probing. Hashing, create an index based on the value of the item that needs to be stored.

1.Usage.php

<?php
// Add stuff to redis
foreach ($userIds as $uuid) {
  $this->indexer->addAtIndex("users", $uuid);
}

// later... retrieve from redis
$userID      =  "fa5352f9-fa1b-48c9-862d-1cb614cc7ed8";
$user        =   $this->indexer->getAtIndex("users", $userID);

var_dump($user);

HashIndex.php

<?php namespace App\Libraries\Analyse;

use Ramsey\Uuid\Uuid;
use App\Libraries\Redis\RedisRepository;

final class HashIndexerUuid
{
    /**
     * @var RedisRepository
     */
    private $repository;

    public function __construct(RedisRepository $redis)
    {
        $this->repository = $redis;
    }

    /**
     * Get at index
     * @param     $group
     * @param     $uuid
     * @param int $increment
     *
     * @return int
     */
    public function getAtIndex($group, $uuid, $increment = 100)
    {
        $index      = $this->lookupIndex($uuid, $increment);
        $uuidBytes  = Uuid::fromString($uuid)->getBytes();

        // When group is empty, just return 0
        if($this->repository->hlen("$group:$index:uuid") === 0) {
            return 0;
        }

        // When group contains uuid, return it
        if($this->repository->hget("$group:$index:uuid", $uuidBytes) !== null) {
            return $this->repository->hget("$group:$index:uuid", $uuidBytes);
        }

        // Else try again
        $increment = $increment + 100;
        return $this->getAtIndex($group, $uuid, $increment); // recursion
    }

    /**
     * Add at index
     * @param     $group
     * @param     $uuid
     * @param     $maxSize
     * @param int $total
     * @param int $increment
     *
     * @return string
     */
    public function addAtIndex($group, $uuid, $maxSize = 768, $total = 1, $increment = 100)
    {
        $index = $this->lookupIndex($uuid, $increment);

        if($this->repository->hlen("$group:$index:uuid") < $maxSize) {
            $this->repository->hset("$group:$index:uuid", Uuid::fromString($uuid)->getBytes(), $total);
            return "$group:$index:uuid";
        }

        $increment = $increment + 100;
        return $this->addAtIndex($group, $uuid, $maxSize, $total, $increment); // recursion
    }

    /**
     * Index lookup table for buckets that have a fixed size.
     *
     * @param     $uuid
     * @param int $increment
     *
     * @return int
     */
    private function lookupIndex($uuid, $increment = 100)
    {
        $key = substr(sha1($uuid), 1, 1);

        $lookup = [
            "a"=>10,"b"=>11,"c"=>12,"d"=>13,"e"=>15,"f"=>16,"g"=>17,"h"=>18,"i"=>19,"j"=>20,"k"=>21,"l"=>22,"m"=>23,
            "n"=>24,"o"=>25,"p"=>26,"q"=>27,"r"=>28,"s"=>29,"t"=>30,"u"=>31,"v"=>32,"w"=>33,"x"=>34,"y"=>35,"z"=>36,
            "0"=>37,"1"=>38,"2"=>39,"3"=>40,"4"=>41,"5"=>42,"6"=>43,"7"=>45,"8"=>46,"9"=>47
        ];

        return $increment+$lookup[$key];
    }
}