MDL-38147 Improvements to caching of course categories, coursecat::get_children() improvements

- Course categories caches are purged by event now
- session cache has additional 10 minutes ttl to clear itself and accomodate for permission changes that do not trigger event purging
- additional request-level cache for coursecat::get()
- We store only children of one category in one cache key
- Function coursecat::get_children() can return results sorted and/or paginated. Added tests

course/lib.php

@@ -2649,6 +2649,7 @@ function move_courses($courseids, $categoryid) {
         }
     }
     fix_course_sortorder();
+    cache_helper::purge_by_event('changesincourse');
 
     return true;
 }
@@ -2828,6 +2829,8 @@ function create_course($data, $editoroptions = NULL) {
     course_create_sections_if_missing($course, 0);
 
     fix_course_sortorder();
+    // purge appropriate caches in case fix_course_sortorder() did not change anything
+    cache_helper::purge_by_event('changesincourse');
 
     // new context created - better mark it as dirty
     mark_context_dirty($context->path);
@@ -2908,6 +2911,8 @@ function update_course($data, $editoroptions = NULL) {
     }
 
     fix_course_sortorder();
+    // purge appropriate caches in case fix_course_sortorder() did not change anything
+    cache_helper::purge_by_event('changesincourse');
 
     // Test for and remove blocks which aren't appropriate anymore
     blocks_remove_inappropriate($course);

course/manage.php

@@ -188,6 +188,7 @@ if ($coursecat->id && $canmanage && $resort && confirm_sesskey()) {
         }
         // This should not be needed but we do it just to be safe.
         fix_course_sortorder();
+        cache_helper::purge_by_event('changesincourse');
     }
 }
 
@@ -233,6 +234,7 @@ if ((!empty($hide) or !empty($show)) && confirm_sesskey()) {
     // Set the visibility of the course. we set the old flag when user manually changes visibility of course.
     $params = array('id' => $course->id, 'visible' => $visible, 'visibleold' => $visible, 'timemodified' => time());
     $DB->update_record('course', $params);
+    cache_helper::purge_by_event('changesincourse');
     add_to_log($course->id, "course", ($visible ? 'show' : 'hide'), "edit.php?id=$course->id", $course->id);
 }
 
@@ -260,6 +262,7 @@ if ((!empty($moveup) or !empty($movedown)) && confirm_sesskey()) {
         }
         $DB->set_field('course', 'sortorder', $swapcourse->sortorder, array('id' => $movecourse->id));
         $DB->set_field('course', 'sortorder', $movecourse->sortorder, array('id' => $swapcourse->id));
+        cache_helper::purge_by_event('changesincourse');
         add_to_log($movecourse->id, "course", "move", "edit.php?id=$movecourse->id", $movecourse->id);
     }
 }

lang/en/cache.php

@@ -36,7 +36,9 @@ $string['cacheadmin'] = 'Cache administration';
 $string['cacheconfig'] = 'Configuration';
 $string['cachedef_calendar_subscriptions'] = 'Calendar subscriptions';
 $string['cachedef_config'] = 'Config settings';
-$string['cachedef_coursecat'] = 'Course categories'; 
+$string['cachedef_coursecat'] = 'Course categories lists for particular user';
+$string['cachedef_coursecatrecords'] = 'Course categories records';
+$string['cachedef_coursecattree'] = 'Course categories tree';
 $string['cachedef_databasemeta'] = 'Database meta information';
 $string['cachedef_eventinvalidation'] = 'Event invalidation';
 $string['cachedef_groupdata'] = 'Course group information';

lib/datalib.php

@@ -951,9 +951,14 @@ function fix_course_sortorder() {
 
     //WARNING: this is PHP5 only code!
 
+    // if there are any changes made to courses or categories we will trigger
+    // the cache events to purge all cached courses/categories data
+    $cacheevents = array();
+
     if ($unsorted = $DB->get_records('course_categories', array('sortorder'=>0))) {
         //move all categories that are not sorted yet to the end
         $DB->set_field('course_categories', 'sortorder', MAX_COURSES_IN_CATEGORY*MAX_COURSE_CATEGORIES, array('sortorder'=>0));
+        $cacheevents['changesincoursecat'] = true;
     }
 
     $allcats = $DB->get_records('course_categories', null, 'sortorder, id', 'id, sortorder, parent, depth, path');
@@ -993,7 +998,9 @@ function fix_course_sortorder() {
     // now walk recursively the tree and fix any problems found
     $sortorder = 0;
     $fixcontexts = array();
-    _fix_course_cats($topcats, $sortorder, 0, 0, '', $fixcontexts);
+    if (_fix_course_cats($topcats, $sortorder, 0, 0, '', $fixcontexts)) {
+        $cacheevents['changesincoursecat'] = true;
+    }
 
     // detect if there are "multiple" frontpage courses and fix them if needed
     $frontcourses = $DB->get_records('course', array('category'=>0), 'id');
@@ -1009,6 +1016,7 @@ function fix_course_sortorder() {
             $DB->set_field('course', 'category', $defaultcat->id, array('id'=>$course->id));
             $context = context_course::instance($course->id);
             $fixcontexts[$context->id] = $context;
+            $cacheevents['changesincourse'] = true;
         }
         unset($frontcourses);
     } else {
@@ -1022,6 +1030,8 @@ function fix_course_sortorder() {
         }
         context_helper::build_all_paths(false);
         unset($fixcontexts);
+        $cacheevents['changesincourse'] = true;
+        $cacheevents['changesincoursecat'] = true;
     }
 
     // release memory
@@ -1032,6 +1042,7 @@ function fix_course_sortorder() {
     // fix frontpage course sortorder
     if ($frontcourse->sortorder != 1) {
         $DB->set_field('course', 'sortorder', 1, array('id'=>$frontcourse->id));
+        $cacheevents['changesincourse'] = true;
     }
 
     // now fix the course counts in category records if needed
@@ -1056,6 +1067,7 @@ function fix_course_sortorder() {
             $str = implode(', ', $categories);
             debugging("The number of courses (category id: $str) has reached MAX_COURSES_IN_CATEGORY (" . MAX_COURSES_IN_CATEGORY . "), it will cause a sorting performance issue, please increase the value of MAX_COURSES_IN_CATEGORY in lib/datalib.php file. See tracker issue: MDL-25669", DEBUG_DEVELOPER);
         }
+        $cacheevents['changesincoursecat'] = true;
     }
 
     // now make sure that sortorders in course table are withing the category sortorder ranges
@@ -1072,6 +1084,7 @@ function fix_course_sortorder() {
                      WHERE category = ?";
             $DB->execute($sql, array($cat->sortorder, $cat->id));
         }
+        $cacheevents['changesincoursecat'] = true;
     }
     unset($fixcategories);
 
@@ -1105,6 +1118,7 @@ function fix_course_sortorder() {
             // it needs full resorting
             $fixcategories[$cat->id] = $cat;
         }
+        $cacheevents['changesincourse'] = true;
     }
     unset($gapcategories);
 
@@ -1116,13 +1130,16 @@ function fix_course_sortorder() {
             if ($course->sortorder != $cat->sortorder + $i) {
                 $course->sortorder = $cat->sortorder + $i;
                 $DB->update_record_raw('course', $course, true);
+                $cacheevents['changesincourse'] = true;
             }
             $i++;
         }
     }
 
-    $coursecatcache = cache::make('core', 'coursecat');
-    $coursecatcache->purge();
+    // advise all caches that need to be rebuilt
+    foreach (array_keys($cacheevents) as $event) {
+        cache_helper::purge_by_event($event);
+    }
 }
 
 /**
@@ -1139,12 +1156,13 @@ function fix_course_sortorder() {
  * @param int $depth
  * @param string $path
  * @param array $fixcontexts
- * @return void
+ * @return bool if changes were made
  */
 function _fix_course_cats($children, &$sortorder, $parent, $depth, $path, &$fixcontexts) {
     global $DB;
 
     $depth++;
+    $changesmade = false;
 
     foreach ($children as $cat) {
         $sortorder = $sortorder + MAX_COURSES_IN_CATEGORY;
@@ -1165,11 +1183,15 @@ function _fix_course_cats($children, &$sortorder, $parent, $depth, $path, &$fixc
         }
         if ($update) {
             $DB->update_record('course_categories', $cat, true);
+            $changesmade = true;
         }
         if (isset($cat->children)) {
-            _fix_course_cats($cat->children, $sortorder, $cat->id, $cat->depth, $cat->path, $fixcontexts);
+            if (_fix_course_cats($cat->children, $sortorder, $cat->id, $cat->depth, $cat->path, $fixcontexts)) {
+                $changesmade = true;
+            }
         }
     }
+    return $changesmade;
 }
 
 /**

lib/db/caches.php

@@ -198,10 +198,31 @@ $definitions = array(
         'persistentmaxsize' => 1,
     ),
 
-    // Used to store data for course categories
-    'coursecat' => array(
+    // Used to store the full tree of course categories
+    'coursecattree' => array(
         'mode' => cache_store::MODE_APPLICATION,
+        'persistent' => true,
+        'invalidationevents' => array(
+            'changesincoursecat',
+        )
+    ),
+    // Used to store data for course categories visible to current user. Helps to browse list of categories
+    'coursecat' => array(
+        'mode' => cache_store::MODE_SESSION,
+        'persistent' => true,
+        'invalidationevents' => array(
+            'changesincoursecat',
+            'changesincourse',
+        ),
+        'ttl' => 600,
+    ),
+    // Used to store data for course categories visible to current user. Helps to browse list of categories
+    'coursecatrecords' => array(
+        'mode' => cache_store::MODE_REQUEST,
         'simplekeys' => true,
         'persistent' => true,
+        'invalidationevents' => array(
+            'changesincoursecat',
+        ),
     ),
 );

lib/tests/coursecatlib_test.php

@@ -239,7 +239,7 @@ class coursecatlib_testcase extends advanced_testcase {
         $this->assertEquals($testdescription, $category1->description);
         $category1 = coursecat::get($category1->id);
         $this->assertEquals($testdescription, $category1->description);
-        coursecat::purge_cache();
+        cache_helper::purge_by_event('changesincoursecat');
         $category1 = coursecat::get($category1->id);
         $this->assertEquals($testdescription, $category1->description);
 
@@ -319,4 +319,44 @@ class coursecatlib_testcase extends advanced_testcase {
         $this->assertEquals(array('id' => $course4->id, 'category' => $category1->id),
                 (array)$DB->get_record_sql('SELECT id, category from {course} where id <> ?', array(SITEID)));
     }
+
+    public function test_get_children() {
+        $category1 = coursecat::create(array('name' => 'Cat1'));
+        $category2 = coursecat::create(array('name' => 'Cat2', 'parent' => $category1->id));
+        $category3 = coursecat::create(array('name' => 'Cat3', 'parent' => $category1->id, 'visible' => 0));
+        $category4 = coursecat::create(array('name' => 'Cat4', 'idnumber' => '12', 'parent' => $category1->id));
+        $category5 = coursecat::create(array('name' => 'Cat5', 'idnumber' => '11', 'parent' => $category1->id, 'visible' => 0));
+        $category6 = coursecat::create(array('name' => 'Cat6', 'idnumber' => '10', 'parent' => $category1->id));
+        $category7 = coursecat::create(array('name' => 'Cat0', 'parent' => $category1->id));
+
+        $children = $category1->get_children();
+        // user does not have the capability to view hidden categories, so the list should be
+        // 2,4,6,7
+        $this->assertEquals(array($category2->id, $category4->id, $category6->id, $category7->id), array_keys($children));
+        $this->assertEquals(4, $category1->get_children_count());
+
+        $children = $category1->get_children(array('offset' => 2));
+        $this->assertEquals(array($category6->id, $category7->id), array_keys($children));
+        $this->assertEquals(4, $category1->get_children_count());
+
+        $children = $category1->get_children(array('limit' => 2));
+        $this->assertEquals(array($category2->id, $category4->id), array_keys($children));
+
+        $children = $category1->get_children(array('offset' => 1, 'limit' => 2));
+        $this->assertEquals(array($category4->id, $category6->id), array_keys($children));
+
+        $children = $category1->get_children(array('sort' => array('name' => 1)));
+        // must be 7,2,4,6
+        $this->assertEquals(array($category7->id, $category2->id, $category4->id, $category6->id), array_keys($children));
+
+        $children = $category1->get_children(array('sort' => array('idnumber' => 1, 'name' => -1)));
+        // must be 2,7,6,4
+        $this->assertEquals(array($category2->id, $category7->id, $category6->id, $category4->id), array_keys($children));
+
+        // check that everything is all right after purging the caches
+        cache_helper::purge_by_event('changesincoursecat');
+        $children = $category1->get_children();
+        $this->assertEquals(array($category2->id, $category4->id, $category6->id, $category7->id), array_keys($children));
+        $this->assertEquals(4, $category1->get_children_count());
+    }
 }
\ No newline at end of file