From 8a592bd55197e057596516f59a378383c54a6078 Mon Sep 17 00:00:00 2001
From: Jonathan Champ <jonathan_champ@ncsu.edu>
Date: Tue, 18 Oct 2011 17:24:59 -0400
Subject: [PATCH 1/2] MDL-29733 grade: Query for Identifying Grade Grades to
 Precreate is SLOW

---
 lib/grade/grade_item.php | 30 ++++++++++++++++++++----------
 1 file changed, 20 insertions(+), 10 deletions(-)

diff --git a/lib/grade/grade_item.php b/lib/grade/grade_item.php
index 8378b78c1f4..c485f65b8c8 100644
--- a/lib/grade/grade_item.php
+++ b/lib/grade/grade_item.php
@@ -1730,16 +1730,26 @@ class grade_item extends grade_object {
             return true; // no need to recalculate locked items
         }
 
-        // precreate grades - we need them to exist
-        $params = array($this->courseid, $this->id, $this->id);
-        $sql = "SELECT DISTINCT go.userid
-                  FROM {grade_grades} go
-                       JOIN {grade_items} gi
-                       ON (gi.id = go.itemid AND gi.courseid = ?)
-                       LEFT OUTER JOIN {grade_grades} g
-                       ON (g.userid = go.userid AND g.itemid = ?)
-                 WHERE gi.id <> ? AND g.id IS NULL";
-        if ($missing = $DB->get_records_sql($sql, $params)) {
+        if ($userid) {
+            $missing = array();
+            if (!$DB->record_exists('grade_grades', array('itemid'=>$this->id, 'userid'=>$userid))) {
+                $m = new stdClass();
+                $m->userid = $userid;
+                $missing[] = $m;
+            }
+        } else {
+            // precreate grades - we need them to exist
+            $params = array($this->courseid, $this->id);
+            $sql = "SELECT go.userid
+                      FROM {grade_grades} go
+                           JOIN {grade_items} gi
+                           ON (gi.id = go.itemid AND gi.courseid = ?)
+                     GROUP BY go.userid
+                     HAVING SUM(go.itemid = ?) = 0";
+            $missing = $DB->get_records_sql($sql, $params);
+        }
+
+        if ($missing) {
             foreach ($missing as $m) {
                 $grade = new grade_grade(array('itemid'=>$this->id, 'userid'=>$m->userid), false);
                 $grade->grade_item =& $this;

From 415b15ccd69183402ff4afab8dfc6444137fdf0d Mon Sep 17 00:00:00 2001
From: Andrew Davis <andrew@moodle.com>
Date: Fri, 24 Aug 2012 11:41:45 +0800
Subject: [PATCH 2/2] MDL-29733 grade: SQL and comment cleanup

---
 lib/grade/grade_item.php | 15 ++++++++-------
 1 file changed, 8 insertions(+), 7 deletions(-)

diff --git a/lib/grade/grade_item.php b/lib/grade/grade_item.php
index c485f65b8c8..46101926021 100644
--- a/lib/grade/grade_item.php
+++ b/lib/grade/grade_item.php
@@ -1730,6 +1730,7 @@ class grade_item extends grade_object {
             return true; // no need to recalculate locked items
         }
 
+        // Precreate grades - we need them to exist
         if ($userid) {
             $missing = array();
             if (!$DB->record_exists('grade_grades', array('itemid'=>$this->id, 'userid'=>$userid))) {
@@ -1738,14 +1739,14 @@ class grade_item extends grade_object {
                 $missing[] = $m;
             }
         } else {
-            // precreate grades - we need them to exist
-            $params = array($this->courseid, $this->id);
-            $sql = "SELECT go.userid
-                      FROM {grade_grades} go
+            // Find any users who have grades for some but not all grade items in this course
+            $params = array('gicourseid' => $this->courseid, 'ggitemid' => $this->id);
+            $sql = "SELECT gg.userid
+                      FROM {grade_grades} gg
                            JOIN {grade_items} gi
-                           ON (gi.id = go.itemid AND gi.courseid = ?)
-                     GROUP BY go.userid
-                     HAVING SUM(go.itemid = ?) = 0";
+                           ON (gi.id = gg.itemid AND gi.courseid = :gicourseid)
+                     GROUP BY gg.userid
+                     HAVING SUM(CASE WHEN gg.itemid = :ggitemid THEN 1 ELSE 0 END) = 0";
             $missing = $DB->get_records_sql($sql, $params);
         }