fix(db): drop index on mail_mailboxes by columns instead of name

appinfo/info.xml

@@ -34,7 +34,7 @@ The rating depends on the installed text processing backend. See [the rating ove
 
 Learn more about the Nextcloud Ethical AI Rating [in our blog](https://nextcloud.com/blog/nextcloud-ethical-ai-rating/).
 	]]></description>
-	<version>5.6.0-alpha.3</version>
+	<version>5.6.0-alpha.4</version>
 	<licence>agpl</licence>
 	<author homepage="https://github.com/ChristophWurst">Christoph Wurst</author>
 	<author homepage="https://github.com/GretaD">GretaD</author>

lib/Migration/Version3500Date20231115184458.php

@@ -28,22 +28,28 @@ public function changeSchema(IOutput $output, Closure $schemaClosure, array $opt
 
 		$mailboxesTable = $schema->getTable('mail_mailboxes');
 
-		$indexNew = 'mail_mb_account_id_name_hash';
-
 		/**
-		 * Variant 1 - with table prefix
+		 * The migration "Version0161Date20190902103701" created a unique index for account_id and name without
+		 * specifying a name. Unfortunately, this resulted in different index names depending on the table
+		 * prefix, which means we now have to loop through the indexes to find the correct one.
+		 *
+		 * This migration is from 2023-11 and, by now, most people should already have it. Although it is not
+		 * recommended to change migrations after they have been released, we are still updating this
+		 * one for correctness as it was supposed to drop the index here.
+		 *
+		 * On newer versions, this will be a no-op, as creating the index
+		 * in "Version0161Date20190902103701" is commented out.
+		 *
+		 * @see \OCA\Mail\Migration\Version0161Date20190902103701::changeSchema
 		 */
-		if ($mailboxesTable->hasIndex('UNIQ_22DEBD839B6B5FBA5E237E06')) {
-			$mailboxesTable->dropIndex('UNIQ_22DEBD839B6B5FBA5E237E06');
-		}
-		/**
-		 * Variant 2 - without table prefix
-		 * @see \OCA\Mail\Migration\Version5006Date20250927130132::changeSchema
-		 */
-		if ($mailboxesTable->hasIndex('UNIQ_45754FF89B6B5FBA5E237E06')) {
-			$mailboxesTable->dropIndex('UNIQ_45754FF89B6B5FBA5E237E06');
+		foreach ($mailboxesTable->getIndexes() as $index) {
+			if ($index->isUnique() && $index->spansColumns(['account_id', 'name'])) {
+				$mailboxesTable->dropIndex($index->getName());
+			}
 		}
 
+		$indexNew = 'mail_mb_account_id_name_hash';
+
 		if (!$mailboxesTable->hasIndex($indexNew)) {
 			$mailboxesTable->addUniqueIndex(['account_id', 'name_hash'], $indexNew);
 		}

lib/Migration/Version5006Date20250927130132.php

@@ -20,20 +20,33 @@
 #[ModifyColumn(table: 'mail_mailboxes', name: 'name', type: ColumnType::STRING, description: 'Increase the column length from 255 to 1024')]
 class Version5006Date20250927130132 extends SimpleMigrationStep {
 
+	/**
+	 * @psalm-param Closure():ISchemaWrapper $schemaClosure
+	 */
 	#[Override]
 	public function changeSchema(IOutput $output, Closure $schemaClosure, array $options): ?ISchemaWrapper {
 		$schema = $schemaClosure();
 
 		$mailboxes = $schema->getTable('mail_mailboxes');
 
 		/**
-		 * Make sure the old account_id+name index is gone. The DB won't allow
-		 * the name length increase otherwise
+		 * The migration "Version0161Date20190902103701" created a unique index for account_id and name without
+		 * specifying a name. Unfortunately, this resulted in different index names depending on the table
+		 * prefix, which means we now have to loop through the indexes to find the correct one.
 		 *
+		 * The index on account_id and name were supposed to be dropped in "Version3500Date20231115184458",
+		 * but this did not work on every setup due to the name mismatch caused by different table prefixes.
+		 *
+		 * Although it is not recommended to change migrations after release,
+		 * we are updating this one with a safeguard to drop any existing index on account_id and name.
+		 *
+		 * @see \OCA\Mail\Migration\Version0161Date20190902103701::changeSchema
 		 * @see \OCA\Mail\Migration\Version3500Date20231115184458::changeSchema
 		 */
-		if ($mailboxes->hasIndex('UNIQ_45754FF89B6B5FBA5E237E06')) {
-			$mailboxes->dropIndex('UNIQ_45754FF89B6B5FBA5E237E06');
+		foreach ($mailboxes->getIndexes() as $index) {
+			if ($index->isUnique() && $index->spansColumns(['account_id', 'name'])) {
+				$mailboxes->dropIndex($index->getName());
+			}
 		}
 
 		$mailboxes->modifyColumn(

lib/Migration/Version5006Date20251015082003.php

@@ -28,9 +28,16 @@ public function changeSchema(IOutput $output, Closure $schemaClosure, array $opt
 		$schema = $schemaClosure();
 
 		/**
-		 * Make sure the old account_id+name index is gone for good
+		 * The migration "Version0161Date20190902103701" created a unique index for account_id and name without
+		 * specifying a name. Unfortunately, this resulted in different index names depending on the table
+		 * prefix, which means we now have to loop through the indexes to find the correct one.
 		 *
+		 * The index on account_id and name were supposed to be dropped in "Version3500Date20231115184458",
+		 * but this did not work on every setup due to the name mismatch caused by different table prefixes.
+		 *
+		 * @see \OCA\Mail\Migration\Version0161Date20190902103701::changeSchema
 		 * @see \OCA\Mail\Migration\Version3500Date20231115184458::changeSchema
+		 * @see \OCA\Mail\Migration\Version5006Date20250927130132::changeSchema
 		 */
 		$mailboxesTable = $schema->getTable('mail_mailboxes');
 		if (!$mailboxesTable->hasIndex('UNIQ_45754FF89B6B5FBA5E237E06')) {

lib/Migration/Version5006Date20251023191023.php

@@ -0,0 +1,60 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * SPDX-FileCopyrightText: 2025 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+namespace OCA\Mail\Migration;
+
+use Closure;
+use OCP\DB\ISchemaWrapper;
+use OCP\Migration\IOutput;
+use OCP\Migration\SimpleMigrationStep;
+use Override;
+
+class Version5006Date20251023191023 extends SimpleMigrationStep {
+
+	/**
+	 * @param Closure(): ISchemaWrapper $schemaClosure
+	 */
+	#[Override]
+	public function changeSchema(IOutput $output, Closure $schemaClosure, array $options): ?ISchemaWrapper {
+		$schema = $schemaClosure();
+
+		$mailboxes = $schema->getTable('mail_mailboxes');
+
+		/**
+		 * The migration "Version0161Date20190902103701" created a unique index for account_id and name without
+		 * specifying a name. Unfortunately, this resulted in different index names depending on the table
+		 * prefix, which means we now have to loop through the indexes to find the correct one.
+		 *
+		 * The index on account_id and name were supposed to be dropped in "Version3500Date20231115184458",
+		 * but this did not work on every setup due to the name mismatch caused by different table prefixes.
+		 *
+		 * On MySQL or MariaDB versions before 10.5, changing the length of the name column to 1024 fails if the
+		 * index on account_id and name still exists, with the error "Specified key was too long; max key length is 3072 bytes."
+		 * However, this change works on MariaDB 10.5 or newer.
+		 *
+		 * The reason is that MariaDB automatically converts a unique index using btree to hash if the key exceeds
+		 * the maximum length and is supported by the storage engine: https://mariadb.com/docs/server/mariadb-quickstart-guides/mariadb-indexes-guide#unique-index
+		 *
+		 * This means that on setups with a different table prefix using MariaDB 10.5, the index on account_id and name
+		 * might still exist. Since we don't need it, we will make another attempt to drop it here.
+		 *
+		 * @see \OCA\Mail\Migration\Version0161Date20190902103701::changeSchema
+		 * @see \OCA\Mail\Migration\Version3500Date20231115184458::changeSchema
+		 * @see \OCA\Mail\Migration\Version5006Date20250927130132::changeSchema
+		 * @see \OCA\Mail\Migration\Version5006Date20251015082003::changeSchema
+		 */
+		foreach ($mailboxes->getIndexes() as $index) {
+			if ($index->isUnique() && $index->spansColumns(['account_id', 'name'])) {
+				$mailboxes->dropIndex($index->getName());
+			}
+		}
+
+		return $schema;
+	}
+}