From 675c2f5341578fa7751d7ec94228deaaeb00083c Mon Sep 17 00:00:00 2001
From: "Andrew Davis (andyjdavis)" <andrew@moodle.com>
Date: Mon, 25 Jul 2011 13:46:49 +0800
Subject: [PATCH] MDL-27845 rating: split the get_ratings() query into two to
 reduce query complexity

---
 rating/lib.php | 41 ++++++++++++++++++++++++-----------------
 1 file changed, 24 insertions(+), 17 deletions(-)

diff --git a/rating/lib.php b/rating/lib.php
index f1a511e6ec3..00b30464b5e 100644
--- a/rating/lib.php
+++ b/rating/lib.php
@@ -567,22 +567,25 @@ class rating_manager {
         $params['component']    = $options->component;
         $params['ratingarea'] = $options->ratingarea;
 
-        $sql = "SELECT r.itemid, r.component, r.ratingarea, r.contextid,
-                       $aggregatestr(r.rating) AS aggrrating, COUNT(r.rating) AS numratings,
-                       ur.id, ur.userid, ur.scaleid, ur.rating AS usersrating
+        $sql = "SELECT r.itemid, r.id, r.userid, r.scaleid, r.rating AS usersrating
+                  FROM {rating} r
+                 WHERE r.userid = :userid AND
+                       r.contextid = :contextid AND
+                       r.itemid {$itemidtest} AND
+                       r.component = :component AND
+                       r.ratingarea = :ratingarea
+              ORDER BY r.itemid";
+        $userratings = $DB->get_records_sql($sql, $params);
+
+        $sql = "SELECT r.itemid, $aggregatestr(r.rating) AS aggrrating, COUNT(r.rating) AS numratings
                   FROM {rating} r
-             LEFT JOIN {rating} ur ON ur.contextid = r.contextid AND
-                                      ur.itemid = r.itemid AND
-                                      ur.component = r.component AND
-                                      ur.ratingarea = r.ratingarea AND
-                                      ur.userid = :userid
                  WHERE r.contextid = :contextid AND
                        r.itemid {$itemidtest} AND
                        r.component = :component AND
                        r.ratingarea = :ratingarea
-              GROUP BY r.itemid, r.component, r.ratingarea, r.contextid, ur.id, ur.userid, ur.scaleid
+              GROUP BY r.itemid, r.component, r.ratingarea, r.contextid
               ORDER BY r.itemid";
-        $ratingsrecords = $DB->get_records_sql($sql, $params);
+        $aggregateratings = $DB->get_records_sql($sql, $params);
 
         $ratingoptions = new stdClass;
         $ratingoptions->context = $options->context;
@@ -590,25 +593,29 @@ class rating_manager {
         $ratingoptions->ratingarea = $options->ratingarea;
         $ratingoptions->settings = $this->generate_rating_settings_object($options);
         foreach ($options->items as $item) {
-            if (array_key_exists($item->{$itemidcol}, $ratingsrecords)) {
+            if (array_key_exists($item->{$itemidcol}, $userratings)) {
                 // Note: rec->scaleid = the id of scale at the time the rating was submitted
                 // may be different from the current scale id
-                $rec = $ratingsrecords[$item->{$itemidcol}];
-                $ratingoptions->itemid = $item->{$itemidcol};
+                $rec = $userratings[$item->{$itemidcol}];
                 $ratingoptions->scaleid = $rec->scaleid;
                 $ratingoptions->userid = $rec->userid;
                 $ratingoptions->id = $rec->id;
-                $ratingoptions->aggregate = min($rec->aggrrating, $ratingoptions->settings->scale->max);
-                $ratingoptions->count = $rec->numratings;
                 $ratingoptions->rating = min($rec->usersrating, $ratingoptions->settings->scale->max);
             } else {
-                $ratingoptions->itemid = $item->{$itemidcol};
                 $ratingoptions->scaleid = null;
                 $ratingoptions->userid = null;
                 $ratingoptions->id = null;
+                $ratingoptions->rating =  null;
+            }
+            if (array_key_exists($item->{$itemidcol}, $aggregateratings)) {
+                $rec = $aggregateratings[$item->{$itemidcol}];
+                $ratingoptions->itemid = $item->{$itemidcol};
+                $ratingoptions->aggregate = min($rec->aggrrating, $ratingoptions->settings->scale->max);
+                $ratingoptions->count = $rec->numratings;
+            } else {
+                $ratingoptions->itemid = $item->{$itemidcol};
                 $ratingoptions->aggregate = null;
                 $ratingoptions->count = 0;
-                $ratingoptions->rating =  null;
             }
 
             $rating = new rating($ratingoptions);