From 3d7f23c5e92d809d50d19fdd0ea7c321ab89b98c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Petr=20S=CC=8Ckoda?= <commits@skodak.org>
Date: Mon, 13 Aug 2012 22:31:36 +0200
Subject: [PATCH] MDL-34864 improve enrol_category sync performance

---
 enrol/category/locallib.php | 15 +++++++--------
 1 file changed, 7 insertions(+), 8 deletions(-)

diff --git a/enrol/category/locallib.php b/enrol/category/locallib.php
index 6a7671b7dbd..2f4c0c1122f 100644
--- a/enrol/category/locallib.php
+++ b/enrol/category/locallib.php
@@ -265,6 +265,7 @@ function enrol_category_sync_full() {
 
     // first of all add necessary enrol instances to all courses
     $parentcat = $DB->sql_concat("cat.path", "'/%'");
+    $parentcctx = $DB->sql_concat("cctx.path", "'/%'");
     // need whole course records to be used by add_instance(), use inner view (ci) to
     // get distinct records only.
     // TODO: Moodle 2.1. Improve enrol API to accept courseid / courserec
@@ -293,12 +294,11 @@ function enrol_category_sync_full() {
     $sql = "SELECT e.*
               FROM {enrol} e
               JOIN {context} ctx ON (ctx.instanceid = e.courseid AND ctx.contextlevel = :courselevel)
-         LEFT JOIN (SELECT DISTINCT cctx.path
-                      FROM {course_categories} cc
+         LEFT JOIN ({course_categories} cc
                       JOIN {context} cctx ON (cctx.instanceid = cc.id AND cctx.contextlevel = :catlevel)
                       JOIN {role_assignments} ra ON (ra.contextid = cctx.id AND ra.roleid $roleids)
-                   ) cat ON (ctx.path LIKE $parentcat)
-             WHERE e.enrol = 'category' AND cat.path IS NULL";
+                   ) ON (ctx.path LIKE $parentcctx)
+             WHERE e.enrol = 'category' AND cc.id IS NULL";
 
     $rs = $DB->get_recordset_sql($sql, $params);
     foreach($rs as $instance) {
@@ -333,12 +333,11 @@ function enrol_category_sync_full() {
               FROM {enrol} e
               JOIN {context} ctx ON (ctx.instanceid = e.courseid AND ctx.contextlevel = :courselevel)
               JOIN {user_enrolments} ue ON (ue.enrolid = e.id)
-         LEFT JOIN (SELECT DISTINCT cctx.path, ra.userid
-                      FROM {course_categories} cc
+         LEFT JOIN ({course_categories} cc
                       JOIN {context} cctx ON (cctx.instanceid = cc.id AND cctx.contextlevel = :catlevel)
                       JOIN {role_assignments} ra ON (ra.contextid = cctx.id AND ra.roleid $roleids)
-                   ) cat ON (ctx.path LIKE $parentcat AND cat.userid = ue.userid)
-             WHERE e.enrol = 'category' AND cat.userid IS NULL";
+                   ) ON (ctx.path LIKE $parentcctx AND ra.userid = ue.userid)
+             WHERE e.enrol = 'category' AND cc.id IS NULL";
     $rs = $DB->get_recordset_sql($sql, $params);
     foreach($rs as $instance) {
         $userid = $instance->userid;