commit 36ff4a498032c9ee986cec4cae03ce899d9d24b2
Author: Russell Smith <russell.smith@latrobe.edu.au>
Date:   Wed Mar 27 15:15:28 2013 +1100

    CONTRIB-4253 Grid Format: Only query mdl_log once per page
    
    mdl_log is a large slow table, instead of running a query each section
    to see if it's been updated, we now run it for the entire subject and
    cache the results.  This means more rows will be returned and the memory
    footprint increased.  However db overhead is significantly reduced.

diff --git a/course/format/grid/renderer.php b/course/format/grid/renderer.php
index 93a8a06..b136d86 100644
--- a/course/format/grid/renderer.php
+++ b/course/format/grid/renderer.php
@@ -264,6 +264,9 @@ class format_grid_renderer extends format_section_renderer_base {
             $str_edit_image_alt = get_string('editimage_alt', 'format_grid');
         }
 
+        // Get all the section information about which items should be marked with the NEW picture
+        $section_updated = $this->new_activity($course);
+
         //start at 1 to skip the summary block
         //or include the summary block if it's in the grid display
         for ($section = $this->topic0_at_top ? 1 : 0; $section <= $course->numsections; $section++) {
@@ -302,7 +305,8 @@ class format_grid_renderer extends format_section_renderer_base {
 
                 echo html_writer::tag('p', $this->section_title($thissection, $course), array('class' => 'icon_content'));
 
-                if ($this->new_activity($thissection, $course)) {
+                if (isset($section_updated[$thissection->id])) {
+                    // The section has been updated since the user last visited this course, add NEW label.
                     echo html_writer::empty_tag('img', array(
                         'class' => 'new_activity',
                         'src' => $url_pic_new_activity,
@@ -550,9 +554,11 @@ class format_grid_renderer extends format_section_renderer_base {
     }
 
 //Checks whether there has been new activity in section $section
-    private function new_activity($section, $course) {
+    private function new_activity($course) {
         global $CFG, $USER, $DB;
 
+        $sections_edited = array();
+
         if (isset($USER->lastcourseaccess[$course->id])) {
             $course->lastaccess = $USER->lastcourseaccess[$course->id];
         } else {
@@ -560,21 +566,18 @@ class format_grid_renderer extends format_section_renderer_base {
         }
 
         $sql = "SELECT id, url FROM {$CFG->prefix}log " .
-                'WHERE course = :courseid AND time > :lastaccess AND action = :edit';
+                "WHERE course = :courseid AND time > :lastaccess AND action = 'editsection'";
 
         $params = array(
             'courseid' => $course->id,
-            'lastaccess' => $course->lastaccess,
-            'edit' => 'editsection');
+            'lastaccess' => $course->lastaccess);
 
         $activity = $DB->get_records_sql($sql, $params);
         foreach ($activity as $url_obj) {
             $list = explode('=', $url_obj->url);
-
-            if ($section->id == $list[1])
-                return true;
+            $sections_edited[$list[1]] = true;
         }
-        return false;
+        return $sections_edited;
     }
 
 }