From d34fa71df400463a6ad2feeebe077b9c70761894 Mon Sep 17 00:00:00 2001
From: sam marshall <s.marshall@open.ac.uk>
Date: Fri, 19 Aug 2016 12:56:42 +0100
Subject: [PATCH] MDL-55628 Completion: Use simpledata for completion cache

The completion cache is currently not marked as simpledata. On the
course page it is frequently retrieved hundreds of times which results
in many calls to the slow unserialize function. By making a slight
change to the data format (using arrays instead of objects) we can
mark it as simpledata, which will avoid using unserialize.
---
 lib/completionlib.php            | 51 ++++++++++++++++----------------
 lib/db/caches.php                |  1 +
 lib/tests/completionlib_test.php |  6 ++--
 3 files changed, 30 insertions(+), 28 deletions(-)

diff --git a/lib/completionlib.php b/lib/completionlib.php
index de9b8a4e639..cba3ed9707a 100644
--- a/lib/completionlib.php
+++ b/lib/completionlib.php
@@ -894,15 +894,16 @@ class completion_info {
         $usecache = $userid == $USER->id;
         $cacheddata = array();
         if ($usecache) {
+            $key = $userid . '_' . $this->course->id;
             if (!isset($this->course->cacherev)) {
                 $this->course = get_course($this->course_id);
             }
-            if ($cacheddata = $completioncache->get($userid . '_' . $this->course->id)) {
+            if ($cacheddata = $completioncache->get($key)) {
                 if ($cacheddata['cacherev'] != $this->course->cacherev) {
                     // Course structure has been changed since the last caching, forget the cache.
                     $cacheddata = array();
-                } else if (array_key_exists($cm->id, $cacheddata)) {
-                    return $cacheddata[$cm->id];
+                } else if (isset($cacheddata[$cm->id])) {
+                    return (object)$cacheddata[$cm->id];
                 }
             }
         }
@@ -921,10 +922,8 @@ class completion_info {
 
             // Reindex by cm id
             $alldata = array();
-            if ($alldatabycmc) {
-                foreach ($alldatabycmc as $data) {
-                    $alldata[$data->coursemoduleid] = $data;
-                }
+            foreach ($alldatabycmc as $data) {
+                $alldata[$data->coursemoduleid] = (array)$data;
             }
 
             // Get the module info and build up condition info for each one
@@ -932,17 +931,17 @@ class completion_info {
                 $modinfo = get_fast_modinfo($this->course, $userid);
             }
             foreach ($modinfo->cms as $othercm) {
-                if (array_key_exists($othercm->id, $alldata)) {
+                if (isset($alldata[$othercm->id])) {
                     $data = $alldata[$othercm->id];
                 } else {
                     // Row not present counts as 'not complete'
-                    $data = new StdClass;
-                    $data->id              = 0;
-                    $data->coursemoduleid  = $othercm->id;
-                    $data->userid          = $userid;
-                    $data->completionstate = 0;
-                    $data->viewed          = 0;
-                    $data->timemodified    = 0;
+                    $data = array();
+                    $data['id'] = 0;
+                    $data['coursemoduleid'] = $othercm->id;
+                    $data['userid'] = $userid;
+                    $data['completionstate'] = 0;
+                    $data['viewed'] = 0;
+                    $data['timemodified'] = 0;
                 }
                 $cacheddata[$othercm->id] = $data;
             }
@@ -954,15 +953,17 @@ class completion_info {
         } else {
             // Get single record
             $data = $DB->get_record('course_modules_completion', array('coursemoduleid'=>$cm->id, 'userid'=>$userid));
-            if ($data == false) {
+            if ($data) {
+                $data = (array)$data;
+            } else {
                 // Row not present counts as 'not complete'
-                $data = new StdClass;
-                $data->id              = 0;
-                $data->coursemoduleid  = $cm->id;
-                $data->userid          = $userid;
-                $data->completionstate = 0;
-                $data->viewed          = 0;
-                $data->timemodified    = 0;
+                $data = array();
+                $data['id'] = 0;
+                $data['coursemoduleid'] = $cm->id;
+                $data['userid'] = $userid;
+                $data['completionstate'] = 0;
+                $data['viewed'] = 0;
+                $data['timemodified'] = 0;
             }
 
             // Put in cache
@@ -971,9 +972,9 @@ class completion_info {
 
         if ($usecache) {
             $cacheddata['cacherev'] = $this->course->cacherev;
-            $completioncache->set($userid . '_' . $this->course->id, $cacheddata);
+            $completioncache->set($key, $cacheddata);
         }
-        return $cacheddata[$cm->id];
+        return (object)$cacheddata[$cm->id];
     }
 
     /**
diff --git a/lib/db/caches.php b/lib/db/caches.php
index 7d90e55efeb..b2be0c03896 100644
--- a/lib/db/caches.php
+++ b/lib/db/caches.php
@@ -221,6 +221,7 @@ $definitions = array(
     'completion' => array(
         'mode' => cache_store::MODE_APPLICATION,
         'simplekeys' => true,
+        'simpledata' => true,
         'ttl' => 3600,
         'staticacceleration' => true,
         'staticaccelerationsize' => 2, // Should be current course and site course.
diff --git a/lib/tests/completionlib_test.php b/lib/tests/completionlib_test.php
index d9a75de7af5..f00447c7cad 100644
--- a/lib/tests/completionlib_test.php
+++ b/lib/tests/completionlib_test.php
@@ -418,7 +418,7 @@ class core_completionlib_testcase extends advanced_testcase {
         $result = $c->get_data($cm);
         $this->assertEquals($sillyrecord, $result);
         $cachevalue = $cache->get('314159_42');
-        $this->assertEquals($sillyrecord, $cachevalue[13]);
+        $this->assertEquals((array)$sillyrecord, $cachevalue[13]);
 
         // 4. Current user, 'whole course', but from cache.
         $result = $c->get_data($cm, true);
@@ -443,8 +443,8 @@ class core_completionlib_testcase extends advanced_testcase {
 
         // Check the cache contents.
         $cachevalue = $cache->get('314159_42');
-        $this->assertEquals($basicrecord, $cachevalue[13]);
-        $this->assertEquals((object)array('id'=>'0', 'coursemoduleid'=>14,
+        $this->assertEquals($basicrecord, (object)$cachevalue[13]);
+        $this->assertEquals(array('id' => '0', 'coursemoduleid' => 14,
             'userid'=>314159, 'completionstate'=>0, 'viewed'=>0, 'timemodified'=>0),
             $cachevalue[14]);
     }