Index: lib/accesslib.php
===================================================================
RCS file: /cvsroot/moodle/moodle/lib/accesslib.php,v
retrieving revision 1.421.2.86
diff -u -r1.421.2.86 accesslib.php
--- lib/accesslib.php	8 Dec 2008 07:28:04 -0000	1.421.2.86
+++ lib/accesslib.php	8 Dec 2008 18:35:47 -0000
@@ -2435,9 +2435,13 @@
  * @param integer $level The context level, for example CONTEXT_COURSE, or CONTEXT_MODULE.
  * @param integer $instance The instance id. For $level = CONTEXT_COURSE, this would be $course->id,
  *      for $level = CONTEXT_MODULE, this would be $cm->id. And so on.
+ * @param object $rs Optional record-set. This should be a record-set resulting
+ *      from a query on the mdl_context table containing at least the fields
+ *      id, instanceid, contextlevel, path, depth. If specified, this function
+ *      just caches all that data, closes the recordset, then returns true
  * @return object The context object.
  */
-function get_context_instance($contextlevel, $instance=0) {
+function get_context_instance($contextlevel, $instance=0, $rs=null) {
 
     global $context_cache, $context_cache_id, $CFG;
     static $allowed_contexts = array(CONTEXT_SYSTEM, CONTEXT_USER, CONTEXT_COURSECAT, CONTEXT_COURSE, CONTEXT_GROUP, CONTEXT_MODULE, CONTEXT_BLOCK);
@@ -2462,6 +2466,19 @@
         error('Error: get_context_instance() called with incorrect context level "'.s($contextlevel).'"');
     }
 
+    if($rs) {
+        // When query is specified, use that query to obtain context records
+        // and automatically cache them
+        $contexts=array();
+        while($context=rs_fetch_next_record($rs)) {
+            $context_cache[$contextlevel][$context->instanceid] = $context;
+            $context_cache_id[$context->id] = $context;
+            $contexts[$context->instanceid]=$context;
+        }
+        rs_close($rs);
+        return $contexts;
+    }
+
     if (!is_array($instance)) {
     /// Check the cache
         if (isset($context_cache[$contextlevel][$instance])) {  // Already cached
@@ -2482,7 +2499,6 @@
         return $context;
     }
 
-
 /// ok, somebody wants to load several contexts to save some db queries ;-)
     $instances = $instance;
     $result = array();
Index: course/lib.php
===================================================================
RCS file: /cvsroot/moodle/moodle/course/lib.php,v
retrieving revision 1.538.2.60
diff -u -r1.538.2.60 lib.php
--- course/lib.php	8 Dec 2008 07:28:05 -0000	1.538.2.60
+++ course/lib.php	8 Dec 2008 18:35:46 -0000
@@ -1088,14 +1088,20 @@
 
     $modlurals = array();
 
-    $cmids    = array();
-    $contexts = null;
-    foreach ($info as $mod) {
-        $cmids[$mod->cm] = $mod->cm;
-    }
-    if ($cmids) {
+    if (count($info)>0) {
         // preload all module contexts with one query
-        $contexts = get_context_instance(CONTEXT_MODULE, $cmids);
+        // note that this join is faster (with large # of activities) than
+        // using an IN clause with the instance numbers
+        $contexts = get_context_instance(CONTEXT_MODULE,0,get_recordset_sql("
+SELECT 
+    x.instanceid, x.id, x.contextlevel, x.path, x.depth
+FROM 
+    {$CFG->prefix}course_modules cm
+    INNER JOIN {$CFG->prefix}context x ON x.instanceid=cm.id
+WHERE
+    cm.course={$course->id}
+    AND x.contextlevel=70 
+"));
     }
 
     foreach ($info as $mod) {