From bb8ad909385a753c7c10b0e466065fcc60861b9c Mon Sep 17 00:00:00 2001
From: Justin Merrill <Justin.Merrill@ethinkeducation.com>
Date: Wed, 3 Nov 2021 12:45:41 -0400
Subject: [PATCH] MDL-72236 forum: index restructure on table forum_read

---
 mod/forum/db/install.xml |  5 ++--
 mod/forum/db/upgrade.php | 51 ++++++++++++++++++++++++++++++++++++++++
 mod/forum/version.php    |  2 +-
 3 files changed, 55 insertions(+), 3 deletions(-)

diff --git a/mod/forum/db/install.xml b/mod/forum/db/install.xml
index bbda97aba99..96c9c7067d2 100644
--- a/mod/forum/db/install.xml
+++ b/mod/forum/db/install.xml
@@ -162,9 +162,10 @@
         <KEY NAME="primary" TYPE="primary" FIELDS="id"/>
       </KEYS>
       <INDEXES>
-        <INDEX NAME="userid-forumid" UNIQUE="false" FIELDS="userid, forumid"/>
-        <INDEX NAME="userid-discussionid" UNIQUE="false" FIELDS="userid, discussionid"/>
+        <INDEX NAME="forumid-userid" UNIQUE="false" FIELDS="forumid, userid"/>
+        <INDEX NAME="discussionid-userid" UNIQUE="false" FIELDS="discussionid, userid"/>
         <INDEX NAME="postid-userid" UNIQUE="false" FIELDS="postid, userid"/>
+        <INDEX NAME="userid" UNIQUE="false" FIELDS="userid"/>
       </INDEXES>
     </TABLE>
     <TABLE NAME="forum_track_prefs" COMMENT="Tracks each users untracked forums">
diff --git a/mod/forum/db/upgrade.php b/mod/forum/db/upgrade.php
index 81ec6a9e29e..c6b87ef583e 100644
--- a/mod/forum/db/upgrade.php
+++ b/mod/forum/db/upgrade.php
@@ -284,5 +284,56 @@ function xmldb_forum_upgrade($oldversion) {
         upgrade_mod_savepoint(true, 2021101100, 'forum');
     }
 
+    if ($oldversion < 2021101101) {
+        // Remove the userid-forumid index as it gets replaces with forumid-userid.
+        $table = new xmldb_table('forum_read');
+        $index = new xmldb_index('userid-forumid', XMLDB_INDEX_NOTUNIQUE, ['userid', 'forumid']);
+
+        // Conditionally launch drop index userid-forumid.
+        if ($dbman->index_exists($table, $index)) {
+            $dbman->drop_index($table, $index);
+        }
+
+        // Remove the userid-discussionid index as it gets replaced with discussionid-userid.
+        $table = new xmldb_table('forum_read');
+        $index = new xmldb_index('userid-discussionid', XMLDB_INDEX_NOTUNIQUE, ['userid', 'discussionid']);
+
+        // Conditionally launch drop index userid-discussionid.
+        if ($dbman->index_exists($table, $index)) {
+            $dbman->drop_index($table, $index);
+        }
+
+        // Define index userid (not unique) to be added to forum_read.
+        $table = new xmldb_table('forum_read');
+        $index = new xmldb_index('userid', XMLDB_INDEX_NOTUNIQUE, ['userid']);
+
+        // Conditionally launch add index userid.
+        if (!$dbman->index_exists($table, $index)) {
+            $dbman->add_index($table, $index);
+        }
+
+        // Build replacement indexes to replace the two dropped earlier.
+        // Define index forumid-userid (not unique) to be added to forum_read.
+        $table = new xmldb_table('forum_read');
+        $index = new xmldb_index('forumid-userid', XMLDB_INDEX_NOTUNIQUE, ['forumid', 'userid']);
+
+        // Conditionally launch add index forumid-userid.
+        if (!$dbman->index_exists($table, $index)) {
+            $dbman->add_index($table, $index);
+        }
+
+        // Define index discussionid-userid (not unique) to be added to forum_read.
+        $table = new xmldb_table('forum_read');
+        $index = new xmldb_index('discussionid-userid', XMLDB_INDEX_NOTUNIQUE, ['discussionid', 'userid']);
+
+        // Conditionally launch add index discussionid-userid.
+        if (!$dbman->index_exists($table, $index)) {
+            $dbman->add_index($table, $index);
+        }
+
+        // Forum savepoint reached.
+        upgrade_mod_savepoint(true, 2021101101, 'forum');
+    }
+
     return true;
 }
diff --git a/mod/forum/version.php b/mod/forum/version.php
index f439dc21aa0..962ba41d9a4 100644
--- a/mod/forum/version.php
+++ b/mod/forum/version.php
@@ -24,6 +24,6 @@
 
 defined('MOODLE_INTERNAL') || die();
 
-$plugin->version   = 2021101100;       // The current module version (Date: YYYYMMDDXX).
+$plugin->version   = 2021101101;       // The current module version (Date: YYYYMMDDXX).
 $plugin->requires  = 2021052500;       // Requires this Moodle version.
 $plugin->component = 'mod_forum';      // Full name of the plugin (used for diagnostics)