From 7ef965ce502ff54ebc79fae73a5a18f5f3f0030a Mon Sep 17 00:00:00 2001
From: Eric Merrill <merrill@oakland.edu>
Date: Tue, 26 Feb 2013 09:48:46 -0500
Subject: [PATCH] MDL-35127 mod_assign More efficient use of expensive database
 queries

Moving two relatively expensive DB queries so they are only executed when needed
instead of on every function call. They will still only execute once, and not
repeatedly during execution of the loop.
---
 mod/assign/lib.php | 67 ++++++++++++++++++++++++----------------------
 1 file changed, 35 insertions(+), 32 deletions(-)

diff --git a/mod/assign/lib.php b/mod/assign/lib.php
index 9b26b123614..3545586357e 100644
--- a/mod/assign/lib.php
+++ b/mod/assign/lib.php
@@ -312,38 +312,6 @@ function assign_print_overview($courses, &$htmlarray) {
     //
     list($sqlassignmentids, $assignmentidparams) = $DB->get_in_or_equal($assignmentids);
 
-    // Build up and array of unmarked submissions indexed by assignment id/ userid
-    // for use where the user has grading rights on assignment.
-    $dbparams = array_merge(array(ASSIGN_SUBMISSION_STATUS_SUBMITTED), $assignmentidparams);
-    $rs = $DB->get_recordset_sql('SELECT
-                                      s.assignment as assignment,
-                                      s.userid as userid,
-                                      s.id as id,
-                                      s.status as status,
-                                      g.timemodified as timegraded
-                                  FROM {assign_submission} s
-                                  LEFT JOIN {assign_grades} g ON
-                                      s.userid = g.userid AND
-                                      s.assignment = g.assignment
-                                  WHERE
-                                      ( g.timemodified is NULL OR
-                                      s.timemodified > g.timemodified ) AND
-                                      s.timemodified IS NOT NULL AND
-                                      s.status = ? AND
-                                      s.assignment ' . $sqlassignmentids, $dbparams);
-
-    $unmarkedsubmissions = array();
-    foreach ($rs as $rd) {
-        $unmarkedsubmissions[$rd->assignment][$rd->userid] = $rd->id;
-    }
-    $rs->close();
-
-
-    // get all user submissions, indexed by assignment id
-    $mysubmissions = $DB->get_records_sql("SELECT a.id AS assignment, a.nosubmissions AS nosubmissions, g.timemodified AS timemarked, g.grader AS grader, g.grade AS grade, s.status AS status
-                            FROM {assign} a LEFT JOIN {assign_grades} g ON g.assignment = a.id AND g.userid = ? LEFT JOIN {assign_submission} s ON s.assignment = a.id AND s.userid = ?
-                            WHERE a.id $sqlassignmentids", array_merge(array($USER->id, $USER->id), $assignmentidparams));
-
     foreach ($assignments as $assignment) {
         // Do not show assignments that are not open
         if (!in_array($assignment->id, $assignmentids)) {
@@ -361,7 +329,33 @@ function assign_print_overview($courses, &$htmlarray) {
         }
         $context = context_module::instance($assignment->coursemodule);
         if (has_capability('mod/assign:grade', $context)) {
+            if (!isset($unmarkedsubmissions)) {
+                // Build up and array of unmarked submissions indexed by assignment id/ userid
+                // for use where the user has grading rights on assignment.
+                $dbparams = array_merge(array(ASSIGN_SUBMISSION_STATUS_SUBMITTED), $assignmentidparams);
+                $rs = $DB->get_recordset_sql('SELECT
+                                                  s.assignment as assignment,
+                                                  s.userid as userid,
+                                                  s.id as id,
+                                                  s.status as status,
+                                                  g.timemodified as timegraded
+                                              FROM {assign_submission} s
+                                              LEFT JOIN {assign_grades} g ON
+                                                  s.userid = g.userid AND
+                                                  s.assignment = g.assignment
+                                              WHERE
+                                                  ( g.timemodified is NULL OR
+                                                  s.timemodified > g.timemodified ) AND
+                                                  s.timemodified IS NOT NULL AND
+                                                  s.status = ? AND
+                                                  s.assignment ' . $sqlassignmentids, $dbparams);
 
+                $unmarkedsubmissions = array();
+                foreach ($rs as $rd) {
+                    $unmarkedsubmissions[$rd->assignment][$rd->userid] = $rd->id;
+                }
+                $rs->close();
+            }
             // count how many people can submit
             $submissions = 0; // init
             if ($students = get_enrolled_users($context, 'mod/assign:view', 0, 'u.id')) {
@@ -377,6 +371,15 @@ function assign_print_overview($courses, &$htmlarray) {
                 $str .= '<div class="details"><a href="'.$link.'">'.get_string('submissionsnotgraded', 'assign', $submissions).'</a></div>';
             }
         } if (has_capability('mod/assign:submit', $context)) {
+            if (!isset($mysubmissions)) {
+                // get all user submissions, indexed by assignment id
+                $mysubmissions = $DB->get_records_sql("SELECT a.id AS assignment, a.nosubmissions AS nosubmissions, g.timemodified
+                                                           AS timemarked, g.grader AS grader, g.grade AS grade, s.status AS status
+                                                           FROM {assign} a LEFT JOIN {assign_grades} g ON g.assignment = a.id AND
+                                                           g.userid = ? LEFT JOIN {assign_submission} s ON s.assignment = a.id AND
+                                                           s.userid = ? WHERE a.id $sqlassignmentids",
+                                                        array_merge(array($USER->id, $USER->id), $assignmentidparams));
+            }
             $str .= '<div class="details">';
             $str .= get_string('mysubmission', 'assign');
             $submission = $mysubmissions[$assignment->id];