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

@@ -894,15 +894,16 @@ public function get_data($cm, $wholecourse = false, $userid = 0, $modinfo = null
         $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];
                 }
             }
         }
@@ -921,28 +922,26 @@ public function get_data($cm, $wholecourse = false, $userid = 0, $modinfo = null
 
             // 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
             if (empty($modinfo)) {
                 $modinfo = get_fast_modinfo($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] = $data;
             }
@@ -954,15 +953,17 @@ public function get_data($cm, $wholecourse = false, $userid = 0, $modinfo = null
         } 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 @@ public function get_data($cm, $wholecourse = false, $userid = 0, $modinfo = null
 
         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];
     }
 
     /**

lib/db/caches.php

@@ -221,6 +221,7 @@
     'completion' => array(
         'mode' => cache_store::MODE_APPLICATION,
         'simplekeys' => true,
+        'simpledata' => true,
         'ttl' => 3600,
         'staticacceleration' => true,
         'staticaccelerationsize' => 2, // Should be current course and site course.

lib/tests/completionlib_test.php

@@ -418,7 +418,7 @@ public function test_get_data() {
         $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 @@ public function test_get_data() {
 
         // 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]);
     }