2 files changed, 107 insertions, 0 deletions
diff --git a/core/Migrations/Version13000Date20170718121200.php b/core/Migrations/Version13000Date20170718121200.php
index d33d489c579..35c2d1730bc 100644
--- a/core/Migrations/Version13000Date20170718121200.php
+++ b/core/Migrations/Version13000Date20170718121200.php
@@ -658,6 +658,7 @@ class Version13000Date20170718121200 extends SimpleMigrationStep {
 			$table->addIndex(['uid'], 'uid_index');
 			$table->addIndex(['type'], 'type_index');
 			$table->addIndex(['category'], 'category_index');
+			$table->addUniqueIndex(['uid', 'type', 'category'], 'unique_category_per_user');
 		}
 
 		if (!$schema->hasTable('vcategory_to_object')) {
diff --git a/core/Migrations/Version32000Date20250731062008.php b/core/Migrations/Version32000Date20250731062008.php
new file mode 100644
index 00000000000..bf15e4a0b22
--- /dev/null
+++ b/core/Migrations/Version32000Date20250731062008.php
@@ -0,0 +1,106 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * SPDX-FileCopyrightText: 2025 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+namespace OC\Core\Migrations;
+
+use Closure;
+use OCP\DB\ISchemaWrapper;
+use OCP\IDBConnection;
+use OCP\Migration\IOutput;
+use OCP\Migration\SimpleMigrationStep;
+use Override;
+
+/**
+ * Make sure vcategory entries are unique per user and type
+ * This migration will clean up existing duplicates
+ * and add a unique constraint to prevent future duplicates.
+ */
+class Version32000Date20250731062008 extends SimpleMigrationStep {
+	public function __construct(
+		private IDBConnection $connection,
+	) {
+	}
+
+	/**
+	 * @param IOutput $output
+	 * @param Closure(): ISchemaWrapper $schemaClosure
+	 * @param array $options
+	 */
+	#[Override]
+	public function preSchemaChange(IOutput $output, Closure $schemaClosure, array $options): void {
+		// Clean up duplicate categories before adding unique constraint
+		$this->cleanupDuplicateCategories($output);
+	}
+
+	/**
+	 * Clean up duplicate categories
+	 */
+	private function cleanupDuplicateCategories(IOutput $output) {
+		$output->info('Starting cleanup of duplicate vcategory records...');
+
+		// Find all categories, ordered to identify duplicates
+		$qb = $this->connection->getQueryBuilder();
+		$qb->select('id', 'uid', 'type', 'category')
+			->from('vcategory')
+			->orderBy('uid')
+			->addOrderBy('type')
+			->addOrderBy('category')
+			->addOrderBy('id');
+
+		$result = $qb->executeQuery();
+
+		$seen = [];
+		$duplicateCount = 0;
+
+		while ($category = $result->fetch()) {
+			$key = $category['uid'] . '|' . $category['type'] . '|' . $category['category'];
+			$categoryId = (int)$category['id'];
+
+			if (!isset($seen[$key])) {
+				// First occurrence - keep this one
+				$seen[$key] = $categoryId;
+				continue;
+			}
+
+			// Duplicate found
+			$keepId = $seen[$key];
+			$duplicateCount++;
+
+			$output->info("Found duplicate: keeping ID $keepId, removing ID $categoryId");
+
+			// Update object references
+			$updateQb = $this->connection->getQueryBuilder();
+			$updateQb->update('vcategory_to_object')
+				->set('categoryid', $updateQb->createNamedParameter($keepId))
+				->where($updateQb->expr()->eq('categoryid', $updateQb->createNamedParameter($categoryId)));
+
+			$affectedRows = $updateQb->executeStatement();
+			if ($affectedRows > 0) {
+				$output->info(" - Updated $affectedRows object references from category $categoryId to $keepId");
+			}
+
+			// Remove duplicate category record
+			$deleteQb = $this->connection->getQueryBuilder();
+			$deleteQb->delete('vcategory')
+				->where($deleteQb->expr()->eq('id', $deleteQb->createNamedParameter($categoryId)));
+
+			$deleteQb->executeStatement();
+			$output->info(" - Deleted duplicate category record ID $categoryId");
+
+		}
+
+		$result->closeCursor();
+
+		if ($duplicateCount === 0) {
+			$output->info('No duplicate categories found');
+		} else {
+			$output->info("Duplicate cleanup completed - processed $duplicateCount duplicates");
+		}
+	}
+}