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<?php
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/*
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* This file is part of the Predis package.
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*
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* (c) Daniele Alessandri <suppakilla@gmail.com>
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*
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* For the full copyright and license information, please view the LICENSE
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* file that was distributed with this source code.
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*/
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require 'SharedConfigurations.php';
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// This is an implementation of an atomic client-side ZPOP using the support for
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// check-and-set (CAS) operations with MULTI/EXEC transactions, as described in
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// "WATCH explained" from http://redis.io/topics/transactions
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//
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// First, populate your database with a tiny sample data set:
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//
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// ./redis-cli
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// SELECT 15
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// ZADD zset 1 a
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// ZADD zset 2 b
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// ZADD zset 3 c
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function zpop($client, $key)
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{
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$element = null;
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$options = array(
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'cas' => true, // Initialize with support for CAS operations
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'watch' => $key, // Key that needs to be WATCHed to detect changes
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'retry' => 3, // Number of retries on aborted transactions, after
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// which the client bails out with an exception.
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);
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$client->transaction($options, function ($tx) use ($key, &$element) {
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@list($element) = $tx->zrange($key, 0, 0);
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if (isset($element)) {
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$tx->multi(); // With CAS, MULTI *must* be explicitly invoked.
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$tx->zrem($key, $element);
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}
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});
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return $element;
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}
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$client = new Predis\Client($single_server);
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$zpopped = zpop($client, 'zset');
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echo isset($zpopped) ? "ZPOPed $zpopped" : "Nothing to ZPOP!", "\n";
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