cache-install.inc

<?php


/**
 * @file
 * Provides a stub cache implementation to be used during installation.
 */

/**
 * Defines a stub cache implementation to be used during installation.
 *
 * The stub implementation is needed when database access is not yet available.
 * Because Drupal's caching system never requires that cached data be present,
 * these stub functions can short-circuit the process and sidestep the need for
 * any persistent storage. Obviously, using this cache implementation during
 * normal operations would have a negative impact on performance.
 */
class DrupalFakeCache extends DrupalDatabaseCache implements DrupalCacheInterface {
    
    /**
     * Overrides DrupalDatabaseCache::get().
     */
    function get($cid) {
        return FALSE;
    }
    
    /**
     * Overrides DrupalDatabaseCache::getMultiple().
     */
    function getMultiple(&$cids) {
        return array();
    }
    
    /**
     * Overrides DrupalDatabaseCache::set().
     */
    function set($cid, $data, $expire = CACHE_PERMANENT) {
    }
    
    /**
     * Overrides DrupalDatabaseCache::clear().
     */
    function clear($cid = NULL, $wildcard = FALSE) {
        // If there is a database cache, attempt to clear it whenever possible. The
        // reason for doing this is that the database cache can accumulate data
        // during installation due to any full bootstraps that may occur at the
        // same time (for example, Ajax requests triggered by the installer). If we
        // didn't try to clear it whenever this function is called, the data in the
        // cache would become stale; for example, the installer sometimes calls
        // variable_set(), which updates the {variable} table and then clears the
        // cache to make sure that the next page request picks up the new value.
        // Not actually clearing the cache here therefore leads old variables to be
        // loaded on the first page requests after installation, which can cause
        // subtle bugs, some of which would not be fixed unless the site
        // administrator cleared the cache manually.
        try {
            if (class_exists('Database')) {
                parent::clear($cid, $wildcard);
            }
        } catch (Exception $e) {
        }
    }
    
    /**
     * Overrides DrupalDatabaseCache::isEmpty().
     */
    function isEmpty() {
        return TRUE;
    }

}