moodle/cache/classes/allow_temporary_caches.php
sam marshall 0b2c2a1f95 MDL-76129 upgrade: Allow caching in specific functions
During install/upgrade, caching is disabled. This change provides a
way to temporarily enable caching (using in-memory cache storage only)
within a specific function; caches are deleted afterwards.

Adding this to two locations improves install performance quite a lot.

Caching is not enabled during the parts of plugin installation that
can vary for individual plugins (install.php/upgrade.php) as these
might be relying on its absence, for example by making direct database
changes.
2022-12-22 11:05:45 +00:00

81 lines
2.9 KiB
PHP

<?php
// This file is part of Moodle - http://moodle.org/
//
// Moodle is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// Moodle is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with Moodle. If not, see <http://www.gnu.org/licenses/>.
namespace core_cache;
/**
* Create and keep an instance of this class to allow temporary caches when caches are disabled.
*
* This class works together with code in {@see cache_factory_disabled}.
*
* The intention is that temporary cache should be short-lived (not for the entire install process),
* which avoids two problems: first, that we might run out of memory for the caches, and second,
* that some code e.g. install.php/upgrade.php files, is entitled to assume that caching is not
* used and make direct database changes.
*
* @package core_cache
* @copyright 2022 The Open University
* @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
*/
class allow_temporary_caches {
/** @var int Number of references of this class; if more than 0, temporary caches are allowed */
protected static $references = 0;
/**
* Constructs an instance of this class.
*
* Temporary caches will be allowed until this instance goes out of scope. Store this token
* in a local variable, so that the caches have a limited life; do not save it outside your
* function.
*
* If cache is not disabled then normal (non-temporary) caches will be used, and this class
* does nothing.
*
* If an object of this class already exists then creating (or destroying) another one will
* have no effect.
*/
public function __construct() {
self::$references++;
}
/**
* Destroys an instance of this class.
*
* You do not need to call this manually; PHP will call it automatically when your variable
* goes out of scope. If you do need to remove your token at other times, use unset($token);
*
* If there are no other instances of this object, then all temporary caches will be discarded.
*/
public function __destruct() {
global $CFG;
require_once($CFG->dirroot . '/cache/disabledlib.php');
self::$references--;
if (self::$references === 0) {
\cache_factory_disabled::clear_temporary_caches();
}
}
/**
* Checks if temp caches are currently allowed.
*
* @return bool True if allowed
*/
public static function is_allowed(): bool {
return self::$references > 0;
}
}