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<?php
// $Id$
/**
* A stub cache implementation to be used during the installation
* process 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 {
function get($cid) {
return FALSE;
}
function getMultiple(&$cids) {
return array();
}
function set($cid, $data, $expire = CACHE_PERMANENT, array $headers = NULL) {
}
function clear($cid = NULL, $wildcard = FALSE) {
// If there is a database cache, attempt to clear it whenever possible. The
// reason for doing this is that the database cache can accumulate data
// during installation due to any full bootstraps that may occur at the
// same time (for example, AJAX requests triggered by the installer). If we
// didn't try to clear it whenever this function is called, the data in the
// cache would become stale; for example, the installer sometimes calls
// variable_set(), which updates the {variable} table and then clears the
// cache to make sure that the next page request picks up the new value.
// Not actually clearing the cache here therefore leads old variables to be
// loaded on the first page requests after installation, which can cause
// subtle bugs, some of which would not be fixed unless the site
// administrator cleared the cache manually.
try {
if (function_exists('drupal_install_initialize_database')) {
drupal_install_initialize_database();
parent::clear($cid, $wildcard);
}
}
// If the attempt at clearing the cache causes an error, that means that
// either the database connection is not set up yet or the relevant cache
// table in the database has not yet been created, so we can safely do
// nothing here.
catch (Exception $e) {
}
}
function isEmpty() {
return TRUE;
}
}
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