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https://github.com/predis/predis.git
synced 2026-08-18 04:01:17 +00:00
Daniele Alessandri
42 lines
1.3 KiB
PHP
42 lines
1.3 KiB
PHP
<?php
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require_once 'SharedConfigurations.php';
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/*
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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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First, populate your database with a tiny sample data set:
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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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*/
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function zpop($client, $zsetKey) {
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$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' => $zsetKey, // Key that needs to be WATCHed to detect changes
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'retry' => 3, // Number of retries on aborted transactions, after
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// which the client bails out with an exception.
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);
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$txReply = $client->multiExec($options, function($tx)
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use ($zsetKey, &$element) {
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@list($element) = $tx->zrange($zsetKey, 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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$tx->zrem($zsetKey, $element);
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}
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});
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return $element;
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}
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$redis = new Predis\Client($single_server, 'dev');
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$zpopped = zpop($redis, 'zset');
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echo isset($zpopped) ? "ZPOPed $zpopped" : "Nothing to ZPOP!", "\n";
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?>
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