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Daniele Alessandri
373d30b070
Status response objects are needed mostly to make it possible from the
client perspective to differentiate a status response with the payload
"OK" from a normale bulk reply containing "OK".
The biggest change is for commands returning +OK responses: these were
previously translated to TRUE (bool value), but they are now returned
as instances of Predis\Response\Status. Just to illustrate an example
of the possibilities with this change we will use SET since it is the
most widely used command returning +OK:
$response = $client->set('foo', 'bar');
echo $response; // 'OK'
$response == 'OK'; // TRUE
isset($response->ok); // TRUE
$response == true; // TRUE
$response === true; // FALSE
$response instanceof Predis\Response\ObjectInterface; // TRUE
$response instanceof Predis\Response\Status; // TRUE
For those checking responses returned by commands such as SET or PONG,
the breaking change basically lies in the usage of strict comparison:
doing $response === true will now evaluate to FALSE instead of TRUE.
By default Predis caches common status responses such as OK or QUEUED
to lower the memory usage when using pipelines or transactions.
53 lines
1.5 KiB
PHP
53 lines
1.5 KiB
PHP
<?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 2 b 3 c
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//
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// Then execute this script four times and see its output.
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//
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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!", PHP_EOL;
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