From 4ee23c10bb365bd23ba26464268230a86e8d0700 Mon Sep 17 00:00:00 2001
From: Damien Bezborodov <dbezborodov@netspot.com.au>
Date: Wed, 25 Jun 2014 17:33:10 +0930
Subject: [PATCH] MDL-45678 assignsubmission_comments: Improve performance for
 permissions checking

---
 lang/en/cache.php       |  1 +
 lib/accesslib.php       | 19 ++++++++++++++++++-
 lib/db/caches.php       |  9 ++++++++-
 lib/enrollib.php        |  3 +++
 mod/assign/locallib.php |  8 +-------
 5 files changed, 31 insertions(+), 9 deletions(-)

diff --git a/lang/en/cache.php b/lang/en/cache.php
index 603746947aa..c033cbcaf5e 100644
--- a/lang/en/cache.php
+++ b/lang/en/cache.php
@@ -46,6 +46,7 @@ $string['cachedef_coursemodinfo'] = 'Accumulated information about modules and s
 $string['cachedef_databasemeta'] = 'Database meta information';
 $string['cachedef_eventinvalidation'] = 'Event invalidation';
 $string['cachedef_externalbadges'] = 'External badges for particular user';
+$string['cachedef_get_suspended_userids'] = 'List of suspended user identifiers per course';
 $string['cachedef_gradecondition'] = 'User grades cached for evaluating conditional availability';
 $string['cachedef_groupdata'] = 'Course group information';
 $string['cachedef_htmlpurifier'] = 'HTML Purifier - cleaned content';
diff --git a/lib/accesslib.php b/lib/accesslib.php
index abcb825587e..37a20769d9d 100644
--- a/lib/accesslib.php
+++ b/lib/accesslib.php
@@ -7445,11 +7445,21 @@ function extract_suspended_users($context, &$users, $ignoreusers=array()) {
  * or enrolment has expired or not started.
  *
  * @param context $context context in which user enrolment is checked.
+ * @param bool $context Enable or disable (default) the request cache
  * @return array list of suspended user id's.
  */
-function get_suspended_userids($context){
+function get_suspended_userids(context $context, $usecache = false) {
     global $DB;
 
+    // Check the cache first for performance reasons if enabled.
+    if ($usecache) {
+        $cache = cache::make('core', 'get_suspended_userids');
+        $susers = $cache->get($context->id);
+        if ($susers !== false) {
+            return $susers;
+        }
+    }
+
     // Get all enrolled users.
     list($sql, $params) = get_enrolled_sql($context);
     $users = $DB->get_records_sql($sql, $params);
@@ -7466,5 +7476,12 @@ function get_suspended_userids($context){
             }
         }
     }
+
+    // Cache results for the remainder of this request.
+    if ($usecache) {
+        $cache->set($context->id, $susers);
+    }
+
+    // Return.
     return $susers;
 }
diff --git a/lib/db/caches.php b/lib/db/caches.php
index c2f99cfd767..24543b9be44 100644
--- a/lib/db/caches.php
+++ b/lib/db/caches.php
@@ -221,5 +221,12 @@ $definitions = array(
         'mode' => cache_store::MODE_SESSION,
         'simplekeys' => true,
         'simpledata' => true
-    )
+    ),
+
+    // For the function get_suspended_userids() in core_access.
+    'get_suspended_userids' => array(
+        'mode' => cache_store::MODE_REQUEST,
+        'simplekeys' => true,
+        'simpledata' => true,
+    ),
 );
diff --git a/lib/enrollib.php b/lib/enrollib.php
index df880d877f0..ce130660812 100644
--- a/lib/enrollib.php
+++ b/lib/enrollib.php
@@ -1404,6 +1404,9 @@ abstract class enrol_plugin {
         $DB->update_record('user_enrolments', $ue);
         context_course::instance($instance->courseid)->mark_dirty(); // reset enrol caches
 
+        // Invalidate core_access cache for get_suspended_userids.
+        cache_helper::invalidate_by_definition('core', 'get_suspended_userids', array(), array($instance->courseid));
+
         // Trigger event.
         $event = \core\event\user_enrolment_updated::create(
                 array(
diff --git a/mod/assign/locallib.php b/mod/assign/locallib.php
index 8a33ff31144..6b475038776 100644
--- a/mod/assign/locallib.php
+++ b/mod/assign/locallib.php
@@ -128,9 +128,6 @@ class assign {
     /** @var bool whether to exclude users with inactive enrolment */
     private $showonlyactiveenrol = null;
 
-    /** @var array list of suspended user IDs in form of ([id1] => id1) */
-    public $susers = null;
-
     /** @var array cached list of participants for this assignment. The cache key will be group, showactive and the context id */
     private $participants = array();
 
@@ -6873,10 +6870,7 @@ class assign {
      * @return bool true is user is active in course.
      */
     public function is_active_user($userid) {
-        if (is_null($this->susers) && !is_null($this->context)) {
-            $this->susers = get_suspended_userids($this->context);
-        }
-        return !in_array($userid, $this->susers);
+        return !in_array($userid, get_suspended_userids($this->context, true));
     }
 }