From 27c4ebdaceb9c5c9b84cb85294912edb47bd04c7 Mon Sep 17 00:00:00 2001
From: Philipp Memmel <philipp.memmel@gmail.com>
Date: Wed, 12 Mar 2025 14:59:06 +0100
Subject: [PATCH] MDL-85034 core_course: Add index to course_sections for
 mod_subsection

This is a backport of MDL-84844.
---
 lib/db/install.xml |  3 ++-
 lib/db/upgrade.php | 12 ++++++++++++
 2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/lib/db/install.xml b/lib/db/install.xml
index b7bd829f0ac..7781ac5f446 100644
--- a/lib/db/install.xml
+++ b/lib/db/install.xml
@@ -1,5 +1,5 @@
 <?xml version="1.0" encoding="UTF-8" ?>
-<XMLDB PATH="lib/db" VERSION="20240923" COMMENT="XMLDB file for core Moodle tables"
+<XMLDB PATH="lib/db" VERSION="20250506" COMMENT="XMLDB file for core Moodle tables"
     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
     xsi:noNamespaceSchemaLocation="../../lib/xmldb/xmldb.xsd"
 >
@@ -395,6 +395,7 @@
       </KEYS>
       <INDEXES>
         <INDEX NAME="course_section" UNIQUE="true" FIELDS="course, section"/>
+        <INDEX NAME="component_itemid" UNIQUE="false" FIELDS="component, itemid" COMMENT="necessary for querying delegated sections"/>
       </INDEXES>
     </TABLE>
     <TABLE NAME="course_request" COMMENT="course requests">
diff --git a/lib/db/upgrade.php b/lib/db/upgrade.php
index c96e5731eed..6a888d4b53d 100644
--- a/lib/db/upgrade.php
+++ b/lib/db/upgrade.php
@@ -1489,5 +1489,17 @@ function xmldb_main_upgrade($oldversion) {
         upgrade_main_savepoint(true, 2024100702.03);
     }
 
+    if ($oldversion < 2024100704.05) {
+        // Add index for querying delegated sections.
+        $table = new xmldb_table('course_sections');
+        $index = new xmldb_index('component_itemid', XMLDB_INDEX_NOTUNIQUE, ['component', 'itemid']);
+
+        if (!$dbman->index_exists($table, $index)) {
+            $dbman->add_index($table, $index);
+        }
+        // Main savepoint reached.
+        upgrade_main_savepoint(true, 2024100704.05);
+    }
+
     return true;
 }