From 5424238aa9e21233d73bc27c95db19c49c6df26d Mon Sep 17 00:00:00 2001
From: Brad Jorsch <bjorsch@wikimedia.org>
Date: Wed, 18 Sep 2019 12:44:15 -0400
Subject: [PATCH] Remove MySQL index aliasing for user_newtalk indexes

While these have not yet caused problems, we should probably deprecate
the whole confusing "index aliasing" feature. Cleaning this up needs to
be done first.

Method MWLBFactory::setSchemaAliases() is being considered private due
to the @internal notation, and so is being removed without deprecation.

Bug: T233240
Change-Id: Ib04b7bc4af53382fde01bd8550cc7e361124255f
---
 includes/ServiceWiring.php                    |  5 +---
 includes/db/MWLBFactory.php                   | 29 -------------------
 includes/installer/MysqlUpdater.php           |  1 +
 ...atch-rename-mysql-user_newtalk-indexes.sql | 10 +++++++
 4 files changed, 12 insertions(+), 33 deletions(-)
 create mode 100644 maintenance/archives/patch-rename-mysql-user_newtalk-indexes.sql

diff --git a/includes/ServiceWiring.php b/includes/ServiceWiring.php
index ab51eabd47..83847d80ae 100644
--- a/includes/ServiceWiring.php
+++ b/includes/ServiceWiring.php
@@ -207,10 +207,7 @@ return [
 		);
 		$class = MWLBFactory::getLBFactoryClass( $lbConf );
 
-		$instance = new $class( $lbConf );
-		MWLBFactory::setSchemaAliases( $instance, $mainConfig->get( 'DBtype' ) );
-
-		return $instance;
+		return new $class( $lbConf );
 	},
 
 	'EventRelayerGroup' => function ( MediaWikiServices $services ) : EventRelayerGroup {
diff --git a/includes/db/MWLBFactory.php b/includes/db/MWLBFactory.php
index ad5708a2f2..63b320e343 100644
--- a/includes/db/MWLBFactory.php
+++ b/includes/db/MWLBFactory.php
@@ -23,7 +23,6 @@
 
 use MediaWiki\Config\ServiceOptions;
 use MediaWiki\Logger\LoggerFactory;
-use Wikimedia\Rdbms\LBFactory;
 use Wikimedia\Rdbms\DatabaseDomain;
 
 /**
@@ -359,34 +358,6 @@ abstract class MWLBFactory {
 		return $class;
 	}
 
-	/**
-	 * @param LBFactory $lbFactory
-	 * @param string $dbType 'mysql', 'sqlite', etc.
-	 * @internal For use with service wiring
-	 */
-	public static function setSchemaAliases( LBFactory $lbFactory, $dbType ) {
-		if ( $dbType === 'mysql' ) {
-			/**
-			 * When SQLite indexes were introduced in r45764, it was noted that
-			 * SQLite requires index names to be unique within the whole database,
-			 * not just within a schema. As discussed in CR r45819, to avoid the
-			 * need for a schema change on existing installations, the indexes
-			 * were implicitly mapped from the new names to the old names.
-			 *
-			 * This mapping can be removed if DB patches are introduced to alter
-			 * the relevant tables in existing installations. Note that because
-			 * this index mapping applies to table creation, even new installations
-			 * of MySQL have the old names (except for installations created during
-			 * a period where this mapping was inappropriately removed, see
-			 * T154872).
-			 */
-			$lbFactory->setIndexAliases( [
-				'un_user_id' => 'user_id',
-				'un_user_ip' => 'user_ip',
-			] );
-		}
-	}
-
 	/**
 	 * Log a database deprecation warning
 	 * @param string $msg Deprecation message
diff --git a/includes/installer/MysqlUpdater.php b/includes/installer/MysqlUpdater.php
index 7d41d04616..a53a72b9d5 100644
--- a/includes/installer/MysqlUpdater.php
+++ b/includes/installer/MysqlUpdater.php
@@ -390,6 +390,7 @@ class MysqlUpdater extends DatabaseUpdater {
 				'patch-drop-archive-ar_usertext_timestamp.sql' ],
 			[ 'dropIndex', 'archive', 'usertext_timestamp', 'patch-drop-archive-usertext_timestamp.sql' ],
 			[ 'dropField', 'logging', 'log_user', 'patch-drop-user-fields.sql' ],
+			[ 'addIndex', 'user_newtalk', 'un_user_ip', 'patch-rename-mysql-user_newtalk-indexes.sql' ],
 		];
 	}
 
diff --git a/maintenance/archives/patch-rename-mysql-user_newtalk-indexes.sql b/maintenance/archives/patch-rename-mysql-user_newtalk-indexes.sql
new file mode 100644
index 0000000000..3177b4d7d3
--- /dev/null
+++ b/maintenance/archives/patch-rename-mysql-user_newtalk-indexes.sql
@@ -0,0 +1,10 @@
+-- T233240: The indexes on `user_newtalk` may be named `un_user_id`/`un_user_ip`
+-- or `user_id`/`user_ip`. At least it won't be both or mixed. Rename them to
+-- the former.
+
+-- Do not use the /*i*/ hack here!
+ALTER TABLE /*_*/user_newtalk
+	DROP INDEX user_id,
+	DROP INDEX user_ip,
+	ADD INDEX un_user_id (user_id),
+	ADD INDEX un_user_ip (user_ip);
-- 
2.20.1