From 3a2e904098a05ab06671be595c6d9afd854fb488 Mon Sep 17 00:00:00 2001
From: sam marshall <s.marshall@open.ac.uk>
Date: Thu, 2 May 2013 15:28:17 +0100
Subject: [PATCH] MDL-39472 MUC: Optimise cache::get_from_persist_cache

---
 cache/classes/helper.php  |  5 +++++
 cache/classes/loaders.php | 15 +++++++++++----
 2 files changed, 16 insertions(+), 4 deletions(-)

diff --git a/cache/classes/helper.php b/cache/classes/helper.php
index 873dbbe6279..6f30b4b2bf9 100644
--- a/cache/classes/helper.php
+++ b/cache/classes/helper.php
@@ -350,6 +350,11 @@ class cache_helper {
      * @param string $definition
      */
     protected static function ensure_ready_for_stats($store, $definition) {
+        // This function is performance-sensitive, so exit as quickly as possible
+        // if we do not need to do anything.
+        if (isset(self::$stats[$definition][$store])) {
+            return;
+        }
         if (!array_key_exists($definition, self::$stats)) {
             self::$stats[$definition] = array(
                 $store => array(
diff --git a/cache/classes/loaders.php b/cache/classes/loaders.php
index 9f7dc79bcca..6f4e680e29a 100644
--- a/cache/classes/loaders.php
+++ b/cache/classes/loaders.php
@@ -912,7 +912,8 @@ class cache implements cache_loader {
      * @return bool
      */
     protected function is_in_persist_cache($key) {
-        if (is_array($key)) {
+        // This method of checking if an array was supplied is faster than is_array.
+        if ($key === (array)$key) {
             $key = $key['key'];
         }
         // This could be written as a single line, however it has been split because the ttl check is faster than the instanceof
@@ -933,10 +934,15 @@ class cache implements cache_loader {
      * @return mixed|false The data from the persist cache or false if it wasn't there.
      */
     protected function get_from_persist_cache($key) {
-        if (is_array($key)) {
+        // This method of checking if an array was supplied is faster than is_array.
+        if ($key === (array)$key) {
             $key = $key['key'];
         }
-        if (!$this->persist || !array_key_exists($key, $this->persistcache)) {
+        // This isset check is faster than array_key_exists but will return false
+        // for null values, meaning null values will come from backing store not
+        // the persist cache. We think this okay because null usage should be
+        // very rare (see comment in MDL-39472).
+        if (!$this->persist || !isset($this->persistcache[$key])) {
             $result = false;
         } else {
             $data = $this->persistcache[$key];
@@ -976,7 +982,8 @@ class cache implements cache_loader {
      * @return bool
      */
     protected function set_in_persist_cache($key, $data) {
-        if (is_array($key)) {
+        // This method of checking if an array was supplied is faster than is_array.
+        if ($key === (array)$key) {
             $key = $key['key'];
         }
         $this->persistcache[$key] = $data;