perf(preview): Optimize migration and simplify DB layout

* Simplify migration by not moving the actual files and just updating the DB * Don't store the storageid in the preview table as it is not needed * Start adding tests Signed-off-by: Carl Schwan <carl.schwan@nextcloud.com>
2026-02-03 20:41:22 -05:00 · 2025-09-10 10:51:41 +02:00 · 2025-09-10 10:51:41 +02:00 · b0357663b9
commit b0357663b9
parent bba9667882
19 changed files with 292 additions and 368 deletions
--- a/apps/files/lib/Command/ScanAppData.php
+++ b/apps/files/lib/Command/ScanAppData.php
@ -51,6 +51,11 @@ class ScanAppData extends Base {
 	}

 	protected function scanFiles(OutputInterface $output, string $folder): int {
+		if ($folder === 'preview') {
+			$output->writeln('<error>Scanning the preview folder is not supported.</error>');
+			return self::FAILURE;
+		}
+
 		try {
 			/** @var Folder $appData */
 			$appData = $this->getAppDataFolder();
--- a/core/BackgroundJobs/MovePreviewJob.php
+++ b/core/BackgroundJobs/MovePreviewJob.php
@ -8,6 +8,7 @@ declare(strict_types=1);

 namespace OC\Core\BackgroundJobs;

+use OC\Files\SimpleFS\SimpleFile;
 use OC\Preview\Db\Preview;
 use OC\Preview\Db\PreviewMapper;
 use OC\Preview\Storage\StorageFactory;
@ -131,11 +132,12 @@ class MovePreviewJob extends TimedJob {
 			$folder = $this->appData->getFolder($internalPath);

 			/**
-			 * @var list<array{file: ISimpleFile, width: int, height: int, crop: bool, max: bool, extension: string, mtime: int, size: int}> $previewFiles
+			 * @var list<array{file: SimpleFile, width: int, height: int, crop: bool, max: bool, extension: string, mtime: int, size: int}> $previewFiles
 			 */
 			$previewFiles = [];

 			foreach ($folder->getDirectoryListing() as $previewFile) {
+				/** @var SimpleFile $previewFile */
 				[0 => $baseName, 1 => $extension] = explode('.', $previewFile->getName());
 				$nameSplit = explode('-', $baseName);

@ -173,7 +175,7 @@ class MovePreviewJob extends TimedJob {
 				foreach ($previewFiles as $previewFile) {
 					$preview = new Preview();
 					$preview->setFileId((int)$fileId);
-					$preview->setStorageId($result[0]['storage']);
+					$preview->setOldFileId($previewFile['file']->getId());
 					$preview->setEtag($result[0]['etag']);
 					$preview->setMtime($previewFile['mtime']);
 					$preview->setWidth($previewFile['width']);
--- a/core/Migrations/Version33000Date20250819110529.php
+++ b/core/Migrations/Version33000Date20250819110529.php
@ -11,12 +11,15 @@ namespace OC\Core\Migrations;
 use Closure;
 use OCP\DB\ISchemaWrapper;
 use OCP\DB\Types;
+use OCP\Migration\Attributes\CreateTable;
 use OCP\Migration\IOutput;
 use OCP\Migration\SimpleMigrationStep;

 /**
 *
 */
+#[CreateTable(table: 'preview', description: 'Holds the preview data')]
+#[CreateTable(table: 'preview_locations', description: 'Holds the preview location in an object store')]
 class Version33000Date20250819110529 extends SimpleMigrationStep {

 	/**
@ -26,21 +29,33 @@ class Version33000Date20250819110529 extends SimpleMigrationStep {
 		/** @var ISchemaWrapper $schema */
 		$schema = $schemaClosure();

+		if (!$schema->hasTable('preview_locations')) {
+			$table = $schema->createTable('preview_locations');
+			$table->addColumn('id', Types::BIGINT, ['autoincrement' => true, 'notnull' => true, 'length' => 20, 'unsigned' => true]);
+			$table->addColumn('bucket_name', Types::STRING, ['notnull' => true, 'length' => 40]);
+			$table->addColumn('object_store_name', Types::STRING, ['notnull' => true, 'length' => 40]);
+			$table->setPrimaryKey(['id']);
+		}
+
 		if (!$schema->hasTable('previews')) {
 			$table = $schema->createTable('previews');
 			$table->addColumn('id', Types::BIGINT, ['autoincrement' => true, 'notnull' => true, 'length' => 20, 'unsigned' => true]);
 			$table->addColumn('file_id', Types::BIGINT, ['notnull' => true, 'length' => 20, 'unsigned' => true]);
-			$table->addColumn('storage_id', Types::BIGINT, ['notnull' => true, 'length' => 20, 'unsigned' => true]);
+			$table->addColumn('old_file_id', Types::BIGINT, ['notnull' => false, 'length' => 20, 'unsigned' => true]);
+			$table->addColumn('location_id', Types::BIGINT, ['notnull' => false, 'length' => 20, 'unsigned' => true]);
 			$table->addColumn('width', Types::INTEGER, ['notnull' => true, 'unsigned' => true]);
 			$table->addColumn('height', Types::INTEGER, ['notnull' => true, 'unsigned' => true]);
 			$table->addColumn('mimetype', Types::INTEGER, ['notnull' => true]);
-			$table->addColumn('is_max', Types::BOOLEAN, ['notnull' => true, 'default' => false]);
-			$table->addColumn('crop', Types::BOOLEAN, ['notnull' => true, 'default' => false]);
-			$table->addColumn('etag', Types::STRING, ['notnull' => true, 'length' => 40]);
+			$table->addColumn('source_mimetype', Types::INTEGER, ['notnull' => true]);
+			$table->addColumn('max', Types::BOOLEAN, ['notnull' => true, 'default' => false]);
+			$table->addColumn('cropped', Types::BOOLEAN, ['notnull' => true, 'default' => false]);
+			$table->addColumn('encrypted', Types::BOOLEAN, ['notnull' => true, 'default' => false]);
+			$table->addColumn('etag', Types::STRING, ['notnull' => true, 'length' => 40, 'fixed' => true]);
 			$table->addColumn('mtime', Types::INTEGER, ['notnull' => true, 'unsigned' => true]);
 			$table->addColumn('size', Types::INTEGER, ['notnull' => true, 'unsigned' => true]);
 			$table->addColumn('version', Types::BIGINT, ['notnull' => true, 'default' => -1]); // can not be null otherwise unique index doesn't work
 			$table->setPrimaryKey(['id']);
+			$table->addIndex(['file_id']);
 			$table->addUniqueIndex(['file_id', 'width', 'height', 'mimetype', 'crop', 'version'], 'previews_file_uniq_idx');
 		}

--- a/lib/composer/composer/LICENSE
+++ b/lib/composer/composer/LICENSE
@ -1,3 +1,4 @@
+
 Copyright (c) Nils Adermann, Jordi Boggiano

 Permission is hereby granted, free of charge, to any person obtaining a copy
@ -17,3 +18,4 @@ AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 THE SOFTWARE.
+
--- a/lib/composer/composer/autoload_classmap.php
+++ b/lib/composer/composer/autoload_classmap.php
@ -1687,7 +1687,6 @@ return array(
    'OC\\Files\\Mount\\MountPoint' => $baseDir . '/lib/private/Files/Mount/MountPoint.php',
    'OC\\Files\\Mount\\MoveableMount' => $baseDir . '/lib/private/Files/Mount/MoveableMount.php',
    'OC\\Files\\Mount\\ObjectHomeMountProvider' => $baseDir . '/lib/private/Files/Mount/ObjectHomeMountProvider.php',
-    'OC\\Files\\Mount\\ObjectStorePreviewCacheMountProvider' => $baseDir . '/lib/private/Files/Mount/ObjectStorePreviewCacheMountProvider.php',
    'OC\\Files\\Mount\\RootMountProvider' => $baseDir . '/lib/private/Files/Mount/RootMountProvider.php',
    'OC\\Files\\Node\\File' => $baseDir . '/lib/private/Files/Node/File.php',
    'OC\\Files\\Node\\Folder' => $baseDir . '/lib/private/Files/Node/Folder.php',
--- a/lib/composer/composer/autoload_static.php
+++ b/lib/composer/composer/autoload_static.php
@ -11,32 +11,32 @@ class ComposerStaticInit749170dad3f5e7f9ca158f5a9f04f6a2
    );

    public static $prefixLengthsPsr4 = array (
-        'O' => 
+        'O' =>
        array (
            'OC\\Core\\' => 8,
            'OC\\' => 3,
            'OCP\\' => 4,
        ),
-        'N' => 
+        'N' =>
        array (
            'NCU\\' => 4,
        ),
    );

    public static $prefixDirsPsr4 = array (
-        'OC\\Core\\' => 
+        'OC\\Core\\' =>
        array (
            0 => __DIR__ . '/../../..' . '/core',
        ),
-        'OC\\' => 
+        'OC\\' =>
        array (
            0 => __DIR__ . '/../../..' . '/lib/private',
        ),
-        'OCP\\' => 
+        'OCP\\' =>
        array (
            0 => __DIR__ . '/../../..' . '/lib/public',
        ),
-        'NCU\\' => 
+        'NCU\\' =>
        array (
            0 => __DIR__ . '/../../..' . '/lib/unstable',
        ),
@ -1728,7 +1728,6 @@ class ComposerStaticInit749170dad3f5e7f9ca158f5a9f04f6a2
        'OC\\Files\\Mount\\MountPoint' => __DIR__ . '/../../..' . '/lib/private/Files/Mount/MountPoint.php',
        'OC\\Files\\Mount\\MoveableMount' => __DIR__ . '/../../..' . '/lib/private/Files/Mount/MoveableMount.php',
        'OC\\Files\\Mount\\ObjectHomeMountProvider' => __DIR__ . '/../../..' . '/lib/private/Files/Mount/ObjectHomeMountProvider.php',
-        'OC\\Files\\Mount\\ObjectStorePreviewCacheMountProvider' => __DIR__ . '/../../..' . '/lib/private/Files/Mount/ObjectStorePreviewCacheMountProvider.php',
        'OC\\Files\\Mount\\RootMountProvider' => __DIR__ . '/../../..' . '/lib/private/Files/Mount/RootMountProvider.php',
        'OC\\Files\\Node\\File' => __DIR__ . '/../../..' . '/lib/private/Files/Node/File.php',
        'OC\\Files\\Node\\Folder' => __DIR__ . '/../../..' . '/lib/private/Files/Node/Folder.php',
--- a/lib/private/Files/Mount/ObjectStorePreviewCacheMountProvider.php
+++ b/lib/private/Files/Mount/ObjectStorePreviewCacheMountProvider.php
@ -1,138 +0,0 @@
-<?php
-
-declare(strict_types=1);
-
-/**
- * SPDX-FileCopyrightText: 2020 Nextcloud GmbH and Nextcloud contributors
- * SPDX-License-Identifier: AGPL-3.0-or-later
- */
-namespace OC\Files\Mount;
-
-use OC\Files\ObjectStore\AppdataPreviewObjectStoreStorage;
-use OC\Files\ObjectStore\ObjectStoreStorage;
-use OC\Files\Storage\Wrapper\Jail;
-use OCP\Files\Config\IRootMountProvider;
-use OCP\Files\Storage\IStorageFactory;
-use OCP\IConfig;
-use Psr\Log\LoggerInterface;
-
-/**
- * Mount provider for object store app data folder for previews
- */
-class ObjectStorePreviewCacheMountProvider implements IRootMountProvider {
-	private LoggerInterface $logger;
-	/** @var IConfig */
-	private $config;
-
-	public function __construct(LoggerInterface $logger, IConfig $config) {
-		$this->logger = $logger;
-		$this->config = $config;
-	}
-
-	/**
-	 * @return MountPoint[]
-	 * @throws \Exception
-	 */
-	public function getRootMounts(IStorageFactory $loader): array {
-		if (!is_array($this->config->getSystemValue('objectstore_multibucket'))) {
-			return [];
-		}
-		if ($this->config->getSystemValue('objectstore.multibucket.preview-distribution', false) !== true) {
-			return [];
-		}
-
-		$instanceId = $this->config->getSystemValueString('instanceid', '');
-		$mountPoints = [];
-		$directoryRange = ['0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f'];
-		$i = 0;
-		foreach ($directoryRange as $parent) {
-			foreach ($directoryRange as $child) {
-				$mountPoints[] = new MountPoint(
-					AppdataPreviewObjectStoreStorage::class,
-					'/appdata_' . $instanceId . '/preview/' . $parent . '/' . $child,
-					$this->getMultiBucketObjectStore($i),
-					$loader,
-					null,
-					null,
-					self::class
-				);
-				$i++;
-			}
-		}
-
-		$rootStorageArguments = $this->getMultiBucketObjectStoreForRoot();
-		$fakeRootStorage = new ObjectStoreStorage($rootStorageArguments);
-		$fakeRootStorageJail = new Jail([
-			'storage' => $fakeRootStorage,
-			'root' => '/appdata_' . $instanceId . '/preview',
-		]);
-
-		// add a fallback location to be able to fetch existing previews from the old bucket
-		$mountPoints[] = new MountPoint(
-			$fakeRootStorageJail,
-			'/appdata_' . $instanceId . '/preview/old-multibucket',
-			null,
-			$loader,
-			null,
-			null,
-			self::class
-		);
-
-		return $mountPoints;
-	}
-
-	protected function getMultiBucketObjectStore(int $number): array {
-		$config = $this->config->getSystemValue('objectstore_multibucket');
-
-		// sanity checks
-		if (empty($config['class'])) {
-			$this->logger->error('No class given for objectstore', ['app' => 'files']);
-		}
-		if (!isset($config['arguments'])) {
-			$config['arguments'] = [];
-		}
-
-		/*
-		 * Use any provided bucket argument as prefix
-		 * and add the mapping from parent/child => bucket
-		 */
-		if (!isset($config['arguments']['bucket'])) {
-			$config['arguments']['bucket'] = '';
-		}
-
-		$config['arguments']['bucket'] .= "-preview-$number";
-
-		// instantiate object store implementation
-		$config['arguments']['objectstore'] = new $config['class']($config['arguments']);
-
-		$config['arguments']['internal-id'] = $number;
-
-		return $config['arguments'];
-	}
-
-	protected function getMultiBucketObjectStoreForRoot(): array {
-		$config = $this->config->getSystemValue('objectstore_multibucket');
-
-		// sanity checks
-		if (empty($config['class'])) {
-			$this->logger->error('No class given for objectstore', ['app' => 'files']);
-		}
-		if (!isset($config['arguments'])) {
-			$config['arguments'] = [];
-		}
-
-		/*
-		 * Use any provided bucket argument as prefix
-		 * and add the mapping from parent/child => bucket
-		 */
-		if (!isset($config['arguments']['bucket'])) {
-			$config['arguments']['bucket'] = '';
-		}
-		$config['arguments']['bucket'] .= '0';
-
-		// instantiate object store implementation
-		$config['arguments']['objectstore'] = new $config['class']($config['arguments']);
-
-		return $config['arguments'];
-	}
-}
--- a/lib/private/Files/ObjectStore/PrimaryObjectStoreConfig.php
+++ b/lib/private/Files/ObjectStore/PrimaryObjectStoreConfig.php
@ -119,12 +119,14 @@ class PrimaryObjectStoreConfig {
 				'default' => 'server1',
 				'server1' => $this->validateObjectStoreConfig($objectStoreMultiBucket),
 				'root' => 'server1',
+				'preview' => 'server1',
 			];
 		} elseif ($objectStore) {
 			if (!isset($objectStore['default'])) {
 				$objectStore = [
 					'default' => 'server1',
 					'root' => 'server1',
+					'preview' => 'server1',
 					'server1' => $objectStore,
 				];
 			}
@ -132,6 +134,10 @@ class PrimaryObjectStoreConfig {
 				$objectStore['root'] = 'default';
 			}

+			if (!isset($objectStore['preview'])) {
+				$objectStore['preview'] = 'default';
+			}
+
 			if (!is_string($objectStore['default'])) {
 				throw new InvalidObjectStoreConfigurationException('The \'default\' object storage configuration is required to be a reference to another configuration.');
 			}
--- a/lib/private/Preview/Db/Preview.php
+++ b/lib/private/Preview/Db/Preview.php
@ -17,8 +17,12 @@ use OCP\IPreview;
 /**
 * @method \int getFileId()
 * @method void setFileId(int $fileId)
- * @method \int getStorageId()
- * @method void setStorageId(\int $fileId)
+ * @method \int getOldFileId() // Old location in the file-cache table, for legacy compatibility
+ * @method void setOldFileId(int $fileId)
+ * @method \int getLocationId()
+ * @method void setLocationId(int $locationId)
+ * @method \string getBucketName()
+ * @method \string getObjectStoreName()
 * @method \int getWidth()
 * @method void setWidth(int $width)
 * @method \int getHeight()
@ -43,7 +47,11 @@ use OCP\IPreview;
 class Preview extends Entity {
 	protected ?int $fileId = null;

-	protected ?int $storageId = null;
+	protected ?int $oldFileId = null;
+
+	protected ?int $locationId = null;
+	protected ?string $bucketName = null;
+	protected ?string $objectStoreName = null;

 	protected ?int $width = null;

@ -65,7 +73,8 @@ class Preview extends Entity {

 	public function __construct() {
 		$this->addType('fileId', Types::BIGINT);
-		$this->addType('storageId', Types::BIGINT);
+		$this->addType('oldFileId', Types::BIGINT);
+		$this->addType('locationId', Types::BIGINT);
 		$this->addType('width', Types::INTEGER);
 		$this->addType('height', Types::INTEGER);
 		$this->addType('mimetype', Types::INTEGER);
@ -108,4 +117,12 @@ class Preview extends Entity {
 			IPreview::MIMETYPE_GIF => 'gif',
 		};
 	}
+
+	public function setBucketName(string $bucketName): void {
+		$this->bucketName = $bucketName;
+	}
+
+	public function setObjectStoreName(string $objectStoreName): void {
+		$this->objectStoreName = $objectStoreName;
+	}
 }
--- a/lib/private/Preview/Db/PreviewMapper.php
+++ b/lib/private/Preview/Db/PreviewMapper.php
@ -22,6 +22,7 @@ use OCP\IPreview;
 class PreviewMapper extends QBMapper {

 	private const TABLE_NAME = 'previews';
+	private const LOCATION_TABLE_NAME = 'preview_locations';

 	public function __construct(IDBConnection $db) {
 		parent::__construct($db, self::TABLE_NAME, Preview::class);
@ -34,8 +35,7 @@ class PreviewMapper extends QBMapper {
 	 */
 	public function getAvailablePreviews(array $fileIds): array {
 		$selectQb = $this->db->getQueryBuilder();
-		$selectQb->select('*')
-			->from(self::TABLE_NAME)
+		$this->joinLocation($selectQb)
 			->where(
 				$selectQb->expr()->in('file_id', $selectQb->createNamedParameter($fileIds, IQueryBuilder::PARAM_INT_ARRAY)),
 			);
@ -48,8 +48,7 @@ class PreviewMapper extends QBMapper {

 	public function getPreview(int $fileId, int $width, int $height, string $mode, int $mimetype = IPreview::MIMETYPE_JPEG): ?Preview {
 		$selectQb = $this->db->getQueryBuilder();
-		$selectQb->select('*')
-			->from(self::TABLE_NAME)
+		$this->joinLocation($selectQb)
 			->where(
 				$selectQb->expr()->eq('file_id', $selectQb->createNamedParameter($fileId)),
 				$selectQb->expr()->eq('width', $selectQb->createNamedParameter($width)),
@ -68,10 +67,9 @@ class PreviewMapper extends QBMapper {
 	 * @param int[] $fileIds
 	 * @return array<int, Preview[]>
 	 */
-	public function getByFileIds(int $storageId, array $fileIds): array {
+	public function getByFileIds(array $fileIds): array {
 		$selectQb = $this->db->getQueryBuilder();
-		$selectQb->select('*')
-			->from(self::TABLE_NAME)
+		$this->joinLocation($selectQb)
 			->where($selectQb->expr()->andX(
 				$selectQb->expr()->in('file_id', $selectQb->createNamedParameter($fileIds, IQueryBuilder::PARAM_INT_ARRAY)),
 			));
@ -85,12 +83,39 @@ class PreviewMapper extends QBMapper {
 	/**
 	 * @param int[] $previewIds
 	 */
-	public function deleteByIds(int $storageId, array $previewIds): void {
+	public function deleteByIds(array $previewIds): void {
 		$qb = $this->db->getQueryBuilder();
 		$qb->delete(self::TABLE_NAME)
 			->where($qb->expr()->andX(
-				$qb->expr()->eq('storage_id', $qb->createNamedParameter($storageId, IQueryBuilder::PARAM_INT)),
 				$qb->expr()->in('id', $qb->createNamedParameter($previewIds, IQueryBuilder::PARAM_INT_ARRAY))
 			))->executeStatement();
 	}
+
+	protected function joinLocation(IQueryBuilder $qb): IQueryBuilder {
+		return $qb->select('p.*', 'l.bucket_name', 'l.object_store_name')
+			->from(self::TABLE_NAME, 'p')
+			->join('p', 'preview_locations', 'l', $qb->expr()->eq(
+			'p.location_id', 'l.id'
+		));
+	}
+
+	public function getLocationId(string $bucket, string $objectStore): int {
+		$qb = $this->db->getQueryBuilder();
+		$result = $qb->select('id')
+			->from(self::LOCATION_TABLE_NAME)
+			->where($qb->expr()->eq('bucket_name', $qb->createNamedParameter($bucket)))
+			->andWhere($qb->expr()->eq('object_store_name', $qb->createNamedParameter($objectStore)))
+			->executeQuery();
+		$data = $result->fetchOne();
+		if ($data) {
+			return $data;
+		} else {
+			$qb->insert(self::LOCATION_TABLE_NAME)
+				->values([
+					'bucket_name' => $qb->createNamedParameter($bucket),
+					'object_store_name' => $qb->createNamedParameter($objectStore),
+				])->executeStatement();
+			return $qb->getLastInsertId();
+		}
+	}
 }
--- a/lib/private/Preview/Generator.php
+++ b/lib/private/Preview/Generator.php
@ -156,17 +156,13 @@ class Generator {

 			// Try to get a cached preview. Else generate (and store) one
 			try {
-				/** @var ISimpleFile $previewFile */
-				$previewFile = null;
-				// TODO(php8.4) replace by array_find
-				foreach ($previews as $p) {
-					if ($p->getWidth() === $width && $p->getHeight() === $height && $p->getMimetype() === $maxPreview->getMimetype() && $p->getVersion() === $previewVersion && $p->getCrop() === $crop) {
-						$previewFile = new PreviewFile($p, $this->storageFactory, $this->previewMapper);
-						break;
-					}
-				}
+				$preview = array_find($previews, fn (Preview $preview): bool => $preview->getWidth() === $width
+					&& $preview->getHeight() === $height && $preview->getMimetype() === $maxPreview->getMimetype()
+					&& $preview->getVersion() === $previewVersion && $preview->getCrop() === $crop);

-				if ($previewFile === null) {
+				if ($preview) {
+					$previewFile = new PreviewFile($preview, $this->storageFactory, $this->previewMapper);
+				} else {
 					if (!$this->previewManager->isMimeSupported($mimeType)) {
 						throw new NotFoundException();
 					}
@ -543,7 +539,6 @@ class Generator {
 	public function savePreview(File $file, int $width, int $height, bool $crop, bool $max, IImage $preview, int $version): Preview {
 		$previewEntry = new Preview();
 		$previewEntry->setFileId($file->getId());
-		$previewEntry->setStorageId((int)$file->getMountPoint()->getNumericStorageId());
 		$previewEntry->setWidth($width);
 		$previewEntry->setHeight($height);
 		$previewEntry->setVersion($version);
--- a/lib/private/Preview/Storage/LocalPreviewStorage.php
+++ b/lib/private/Preview/Storage/LocalPreviewStorage.php
@ -18,30 +18,35 @@ use OCP\IConfig;

 class LocalPreviewStorage implements IPreviewStorage {
 	private const PREVIEW_DIRECTORY = '__preview';
-
 	private readonly string $rootFolder;
+	private readonly string $instanceId;

 	public function __construct(
 		private readonly IConfig $config,
 	) {
+		$this->instanceId = $this->config->getSystemValueString('instanceid');
 		$this->rootFolder = $this->config->getSystemValue('datadirectory', OC::$SERVERROOT . '/data');
 	}

 	public function writePreview(Preview $preview, $stream): false|int {
 		$previewPath = $this->constructPath($preview);
 		$this->createParentFiles($previewPath);
-		$file = @fopen($this->rootFolder . '/' . self::PREVIEW_DIRECTORY . '/' . $previewPath, 'w');
+		$file = @fopen($this->getPreviewRootFolder() . $previewPath, 'w');
 		return fwrite($file, $stream);
 	}

 	public function readPreview(Preview $preview) {
 		$previewPath = $this->constructPath($preview);
-		return @fopen($this->rootFolder . '/' . self::PREVIEW_DIRECTORY . '/' . $previewPath, 'r');
+		return @fopen($this->getPreviewRootFolder() . $previewPath, 'r');
 	}

 	public function deletePreview(Preview $preview) {
 		$previewPath = $this->constructPath($preview);
-		@unlink($this->rootFolder . '/' . self::PREVIEW_DIRECTORY . '/' . $previewPath);
+		@unlink($this->getPreviewRootFolder() . $previewPath);
+	}
+
+	public function getPreviewRootFolder(): string {
+		return $this->rootFolder . '/appdata_' . $this->instanceId . '/preview/';
 	}

 	private function constructPath(Preview $preview): string {
@ -63,11 +68,14 @@ class LocalPreviewStorage implements IPreviewStorage {
 		$previewPath = $this->constructPath($preview);
 		$sourcePath = $this->rootFolder . '/appdata_' . $instanceId . '/preview/' . $previewPath;
 		$destinationPath = $this->rootFolder . '/' . self::PREVIEW_DIRECTORY . '/' . $previewPath;
-		if (!file_exists($sourcePath)) {
-			// legacy flat directory
-			$sourcePath = $this->rootFolder . '/appdata_' . $instanceId . '/preview/' . $preview->getFileId() . '/' . $preview->getName();
+		if (file_exists($sourcePath)) {
+			return; // No need to migrate
 		}
+
+		// legacy flat directory
+		$sourcePath = $this->rootFolder . '/appdata_' . $instanceId . '/preview/' . $preview->getFileId() . '/' . $preview->getName();
 		if (file_exists($destinationPath)) {
+			@unlink($sourcePath); // We already have a new preview, just delete the old one
 			return;
 		}
 		$this->createParentFiles($previewPath);
--- a/lib/private/Preview/Storage/ObjectStorePreviewStorage.php
+++ b/lib/private/Preview/Storage/ObjectStorePreviewStorage.php
@ -14,28 +14,29 @@ use Icewind\Streams\CountWrapper;
 use OC\Files\ObjectStore\PrimaryObjectStoreConfig;
 use OC\Files\SimpleFS\SimpleFile;
 use OC\Preview\Db\Preview;
+use OC\Preview\Db\PreviewMapper;
 use OCP\Files\NotFoundException;
 use OCP\Files\ObjectStore\IObjectStore;
 use OCP\IConfig;

 /**
- * @psalm-type ObjectStoreDefinition = array{store: IObjectStore, objectPrefix: string, config?: array}
+ * @psalm-import-type ObjectStoreConfig from PrimaryObjectStoreConfig
+ * @psalm-type ObjectStoreDefinition = array{store: IObjectStore, objectPrefix: string, config?: ObjectStoreConfig}
 */
 class ObjectStorePreviewStorage implements IPreviewStorage {

 	/**
-	 * @var array<'root'|int, ObjectStoreDefinition>
+	 * @var array<string, array<int, ObjectStoreDefinition>>
 	 */
 	private array $objectStoreCache = [];

-	private bool $isMultibucketEnabled;
 	private bool $isMultibucketPreviewDistributionEnabled;

 	public function __construct(
 		private readonly PrimaryObjectStoreConfig $objectStoreConfig,
-		readonly private IConfig $config,
+		IConfig $config,
+		readonly private PreviewMapper $previewMapper,
 	) {
-		$this->isMultibucketEnabled = is_array($config->getSystemValue('objectstore_multibucket'));
 		$this->isMultibucketPreviewDistributionEnabled = $config->getSystemValueBool('objectstore.multibucket.preview-distribution');
 	}

@ -56,6 +57,7 @@ class ObjectStorePreviewStorage implements IPreviewStorage {
 		[
 			'objectPrefix' => $objectPrefix,
 			'store' => $store,
+			'config' => $config,
 		] = $this->getObjectStoreForPreview($preview);

 		$store->writeObject($this->constructUrn($objectPrefix, $preview->getId()), $countStream);
@ -79,102 +81,72 @@ class ObjectStorePreviewStorage implements IPreviewStorage {
 	}

 	public function migratePreview(Preview $preview, SimpleFile $file): void {
-		foreach ([false, true] as $fallback) {
-			[
-				'objectPrefix' => $objectPrefix,
-				'store' => $store,
-				'config' => $config,
-			] = $this->getObjectStoreForPreview($preview, $fallback);
-
-			$oldObjectPrefix = 'urn:oid:';
-			if (isset($config['objectPrefix'])) {
-				$oldObjectPrefix = $config['objectPrefix'];
-			}
-
-			try {
-				$store->copyObject($this->constructUrn($oldObjectPrefix, $file->getId()), $this->constructUrn($objectPrefix, $preview->getId()));
-				break;
-			} catch (NotFoundException $e) {
-				if (!$fallback && $this->isMultibucketPreviewDistributionEnabled) {
-					continue;
-				}
-				throw $e;
-			}
-		}
-	}
-
-	/**
-	 * @return ObjectStoreDefinition
-	 */
-	private function getMultiBucketObjectStore(int $number): array {
-		/**
-		 * @var array{class: class-string<IObjectStore>, ...} $config
-		 */
-		$config = $this->config->getSystemValue('objectstore_multibucket');
-
-		if (!isset($config['arguments'])) {
-			$config['arguments'] = [];
-		}
-
-		/*
-		 * Use any provided bucket argument as prefix
-		 * and add the mapping from parent/child => bucket
-		 */
-		if (!isset($config['arguments']['bucket'])) {
-			$config['arguments']['bucket'] = '';
-		}
-
-		$config['arguments']['bucket'] .= "-preview-$number";
-
-		$objectPrefix = 'urn:oid:preview:';
-		if (isset($config['objectPrefix'])) {
-			$objectPrefix = $config['objectPrefix'] . 'preview:';
-		}
-
-		return [
-			'store' => new $config['class']($config['arguments']),
-			'objectPrefix' => $objectPrefix,
-			'config' => $config,
-		];
-	}
-
-	/**
-	 * @return ObjectStoreDefinition
-	 */
-	private function getRootObjectStore(): array {
-		if (!isset($this->objectStoreCache['root'])) {
-			$rootConfig = $this->objectStoreConfig->getObjectStoreConfigForRoot();
-			$objectPrefix = 'urn:oid:preview:';
-			if (isset($rootConfig['arguments']['objectPrefix'])) {
-				$objectPrefix = $rootConfig['arguments']['objectPrefix'] . 'preview:';
-			}
-			$this->objectStoreCache['root'] = [
-				'store' => $this->objectStoreConfig->buildObjectStore($rootConfig),
-				'objectPrefix' => $objectPrefix,
-			];
-		}
-		return $this->objectStoreCache['root'];
+		// Just set the Preview::bucket and Preview::objectStore
+		$this->getObjectStoreForPreview($preview, true);
 	}

 	/**
 	 * @return ObjectStoreDefinition
 	 */
 	private function getObjectStoreForPreview(Preview $preview, bool $oldFallback = false): array {
-		if (!$this->isMultibucketEnabled || !$this->isMultibucketPreviewDistributionEnabled || $oldFallback) {
-			return $this->getRootObjectStore();
+		if ($preview->getObjectStoreName() === null) {
+			$config = $this->objectStoreConfig->getObjectStoreConfiguration($oldFallback ? 'root' : 'preview');
+			$objectStoreName = $this->objectStoreConfig->resolveAlias($oldFallback ? 'root' : 'preview');
+
+			$bucketName = $config['arguments']['bucket'];
+			if ($config['arguments']['multibucket']) {
+				if ($this->isMultibucketPreviewDistributionEnabled) {
+					$oldLocationArray = str_split(substr(md5((string)$preview->getFileId()), 0, 2));
+					$bucketNumber = hexdec('0x' . $oldLocationArray[0]) * 16 + hexdec('0x' . $oldLocationArray[0]);
+					$bucketName .= '-preview-' . $bucketNumber;
+				} else {
+					$bucketName .= '0';
+				}
+			}
+			$config['arguments']['bucket'] = $bucketName;
+
+			$locationId = $this->previewMapper->getLocationId($bucketName, $objectStoreName);
+			$preview->setLocationId($locationId);
+			$preview->setObjectStoreName($objectStoreName);
+			$preview->setBucketName($bucketName);
+		} else {
+			$config = $this->objectStoreConfig->getObjectStoreConfiguration($preview->getObjectStoreName());
+			$config['arguments']['bucket'] = $bucketName = $preview->getBucketName();
+			$objectStoreName = $preview->getObjectStoreName();
 		}

-		$oldLocationArray = str_split(substr(md5((string)$preview->getFileId()), 0, 2));
-		$bucketNumber = hexdec('0x' . $oldLocationArray[0]) * 16 + hexdec('0x' . $oldLocationArray[0]);
+		$objectPrefix = $this->getObjectPrefix($preview, $config);

-		if (!isset($this->objectStoreCache[$bucketNumber])) {
-			$this->objectStoreCache[$bucketNumber] = $this->getMultiBucketObjectStore($bucketNumber);
+		if (!isset($this->objectStoreCache[$objectStoreName])) {
+			$this->objectStoreCache[$objectStoreName] = [];
+			$this->objectStoreCache[$objectStoreName][$bucketName] = [
+				'store' => $this->objectStoreConfig->buildObjectStore($config),
+				'objectPrefix' => $objectPrefix,
+				'config' => $config,
+			];
+		} elseif (!isset($this->objectStoreCache[$objectStoreName][$bucketName])) {
+			$this->objectStoreCache[$objectStoreName][$bucketName] = [
+				'store' => $this->objectStoreConfig->buildObjectStore($config),
+				'objectPrefix' => $objectPrefix,
+				'config' => $config,
+			];
 		}

-		return $this->objectStoreCache[$bucketNumber];
+		return $this->objectStoreCache[$objectStoreName][$bucketName];
 	}

 	private function constructUrn(string $objectPrefix, int $id): string {
 		return $objectPrefix . $id;
 	}
+
+	public function getObjectPrefix(Preview $preview, array $config): string {
+		if ($preview->getOldFileId()) {
+			return $config['arguments']['objectPrefix'] ?? 'uri:oid:';
+		}
+		if (isset($config['arguments']['objectPrefix'])) {
+			return $config['arguments']['objectPrefix'] . 'preview:';
+		} else {
+			return 'uri:oid:preview:';
+		}
+	}
 }
--- a/lib/private/Preview/Storage/StorageFactory.php
+++ b/lib/private/Preview/Storage/StorageFactory.php
@ -5,6 +5,7 @@ namespace OC\Preview\Storage;
 use OC\Files\ObjectStore\PrimaryObjectStoreConfig;
 use OC\Files\SimpleFS\SimpleFile;
 use OC\Preview\Db\Preview;
+use OC\Preview\Db\PreviewMapper;
 use OCP\IConfig;

 class StorageFactory implements IPreviewStorage {
@ -13,6 +14,7 @@ class StorageFactory implements IPreviewStorage {
 	public function __construct(
 		private readonly PrimaryObjectStoreConfig $objectStoreConfig,
 		private readonly IConfig $config,
+		private readonly PreviewMapper $previewMapper,
 	) {
 	}

@ -34,7 +36,7 @@ class StorageFactory implements IPreviewStorage {
 		}

 		if ($this->objectStoreConfig->hasObjectStore()) {
-			$this->backend = new ObjectStorePreviewStorage($this->objectStoreConfig, $this->config);
+			$this->backend = new ObjectStorePreviewStorage($this->objectStoreConfig, $this->config, $this->previewMapper);
 		} else {
 			$this->backend = new LocalPreviewStorage($this->config);
 		}
--- a/lib/private/Server.php
+++ b/lib/private/Server.php
@ -49,7 +49,6 @@ use OC\Files\Lock\LockManager;
 use OC\Files\Mount\CacheMountProvider;
 use OC\Files\Mount\LocalHomeMountProvider;
 use OC\Files\Mount\ObjectHomeMountProvider;
-use OC\Files\Mount\ObjectStorePreviewCacheMountProvider;
 use OC\Files\Mount\RootMountProvider;
 use OC\Files\Node\HookConnector;
 use OC\Files\Node\LazyRoot;
@ -789,7 +788,6 @@ class Server extends ServerContainer implements IServerContainer {
 			$manager->registerHomeProvider(new LocalHomeMountProvider());
 			$manager->registerHomeProvider(new ObjectHomeMountProvider($objectStoreConfig));
 			$manager->registerRootProvider(new RootMountProvider($objectStoreConfig, $config));
-			$manager->registerRootProvider(new ObjectStorePreviewCacheMountProvider($logger, $config));

 			return $manager;
 		});
--- a/tests/lib/Files/Mount/ObjectStorePreviewCacheMountProviderTest.php
+++ b/tests/lib/Files/Mount/ObjectStorePreviewCacheMountProviderTest.php
@ -1,95 +0,0 @@
-<?php
-
-declare(strict_types=1);
-/**
- * SPDX-FileCopyrightText: 2020 Nextcloud GmbH and Nextcloud contributors
- * SPDX-License-Identifier: AGPL-3.0-or-later
- */
-
-namespace Test\Files\Mount;
-
-use OC\Files\Mount\ObjectStorePreviewCacheMountProvider;
-use OC\Files\ObjectStore\S3;
-use OC\Files\Storage\StorageFactory;
-use OCP\Files\Storage\IStorageFactory;
-use OCP\IConfig;
-use PHPUnit\Framework\MockObject\MockObject;
-use Psr\Log\LoggerInterface;
-
-/**
- * @group DB
- *
- * The DB permission is needed for the fake root storage initialization
- */
-class ObjectStorePreviewCacheMountProviderTest extends \Test\TestCase {
-	/** @var ObjectStorePreviewCacheMountProvider */
-	protected $provider;
-
-	/** @var LoggerInterface|MockObject */
-	protected $logger;
-	/** @var IConfig|MockObject */
-	protected $config;
-	/** @var IStorageFactory|MockObject */
-	protected $loader;
-
-
-	protected function setUp(): void {
-		parent::setUp();
-
-		$this->logger = $this->createMock(LoggerInterface::class);
-		$this->config = $this->createMock(IConfig::class);
-		$this->loader = $this->createMock(StorageFactory::class);
-
-		$this->provider = new ObjectStorePreviewCacheMountProvider($this->logger, $this->config);
-	}
-
-	public function testNoMultibucketObjectStorage(): void {
-		$this->config->expects($this->once())
-			->method('getSystemValue')
-			->with('objectstore_multibucket')
-			->willReturn(null);
-
-		$this->assertEquals([], $this->provider->getRootMounts($this->loader));
-	}
-
-	public function testMultibucketObjectStorage(): void {
-		$objectstoreConfig = [
-			'class' => S3::class,
-			'arguments' => [
-				'bucket' => 'abc',
-				'num_buckets' => 64,
-				'key' => 'KEY',
-				'secret' => 'SECRET',
-				'hostname' => 'IP',
-				'port' => 'PORT',
-				'use_ssl' => false,
-				'use_path_style' => true,
-			],
-		];
-		$this->config->expects($this->any())
-			->method('getSystemValue')
-			->willReturnCallback(function ($config) use ($objectstoreConfig) {
-				if ($config === 'objectstore_multibucket') {
-					return $objectstoreConfig;
-				} elseif ($config === 'objectstore.multibucket.preview-distribution') {
-					return true;
-				}
-				return null;
-			});
-		$this->config->expects($this->once())
-			->method('getSystemValueString')
-			->with('instanceid')
-			->willReturn('INSTANCEID');
-
-		$mounts = $this->provider->getRootMounts($this->loader);
-
-		// 256 mounts for the subfolders and 1 for the fake root
-		$this->assertCount(257, $mounts);
-
-		// do some sanity checks if they have correct mount point paths
-		$this->assertEquals('/appdata_INSTANCEID/preview/0/0/', $mounts[0]->getMountPoint());
-		$this->assertEquals('/appdata_INSTANCEID/preview/2/5/', $mounts[37]->getMountPoint());
-		// also test the path of the fake bucket
-		$this->assertEquals('/appdata_INSTANCEID/preview/old-multibucket/', $mounts[256]->getMountPoint());
-	}
-}
--- a/tests/lib/Files/Storage/Storage.php
+++ b/tests/lib/Files/Storage/Storage.php
@ -358,6 +358,7 @@ abstract class Storage extends \Test\TestCase {
 		$this->assertTrue($this->instance->file_exists($fileName));

 		$fh = $this->instance->fopen($fileName, 'r');
+		$this->assertTrue(is_resource($fh));
 		$content = stream_get_contents($fh);
 		$this->assertEquals(file_get_contents($textFile), $content);
 	}
--- a/tests/lib/Preview/MovePreviewJobTest.php
+++ b/tests/lib/Preview/MovePreviewJobTest.php
@ -0,0 +1,32 @@
+<?php
+
+namespace lib\Preview;
+
+use OC\Core\BackgroundJobs\MovePreviewJob;
+use OCP\Files\AppData\IAppDataFactory;
+use OCP\Files\IAppData;
+use OCP\Server;
+use PHPUnit\Framework\Attributes\CoversClass;
+use PHPUnit\Framework\Attributes\TestDox;
+use Test\TestCase;
+
+/**
+ * @group DB
+ */
+#[CoversClass(MovePreviewJob::class)]
+class MovePreviewJobTest extends TestCase {
+	private IAppData $previewAppData;
+
+	public function setUp(): void {
+		parent::setUp();
+		$this->previewAppData = Server::get(IAppDataFactory::class)->get('preview');
+	}
+
+	#[TestDox("Test the migration from the legacy flat hierarchy to the new one")]
+	function testMigrationLegacyPath(): void {
+		$folder = $this->previewAppData->newFolder(5);
+		$file = $folder->newFile('64-64-crop.png', 'abcdefg');
+		$job = Server::get(MovePreviewJob::class);
+		$this->invokePrivate($job, 'run', []);
+	}
+}
--- a/tests/lib/Preview/PreviewMapperTest.php
+++ b/tests/lib/Preview/PreviewMapperTest.php
@ -0,0 +1,79 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * SPDX-FileCopyrightText: 2025 Nextcloud GmbH
+ * SPDX-FileContributor: Carl Schwan
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+namespace Test\Preview;
+
+use OC\Preview\Db\Preview;
+use OC\Preview\Db\PreviewMapper;
+use OCP\IDBConnection;
+use OCP\IPreview;
+use OCP\Server;
+use Test\TestCase;
+
+/**
+ * @group DB
+ */
+class PreviewMapperTest extends TestCase {
+	private PreviewMapper $previewMapper;
+	private IDBConnection $connection;
+
+	public function setUp(): void {
+		$this->previewMapper = Server::get(PreviewMapper::class);
+		$this->connection = Server::get(IDBConnection::class);
+	}
+
+	public function testGetAvailablePreviews() {
+		// Empty
+		$this->assertEquals([], $this->previewMapper->getAvailablePreviews([]));
+
+		// No preview available
+		$this->assertEquals([42 => []], $this->previewMapper->getAvailablePreviews([42]));
+
+		$this->createPreviewForFileId(42);
+		$previews = $this->previewMapper->getAvailablePreviews([42]);
+		$this->assertNotEmpty($previews[42]);
+		$this->assertNull($previews[42][0]->getLocationId());
+		$this->assertNull($previews[42][0]->getBucketName());
+		$this->assertNull($previews[42][0]->getObjectStoreName());
+
+		$this->createPreviewForFileId(43, 2);
+		$previews = $this->previewMapper->getAvailablePreviews([43]);
+		$this->assertNotEmpty($previews[43]);
+		$this->assertEquals('preview-2', $previews[43][0]->getBucketName());
+		$this->assertEquals('default', $previews[43][0]->getObjectStoreName());
+	}
+
+	private function createPreviewForFileId(int $fileId, ?int $bucket = null) {
+		if ($bucket) {
+			$qb = $this->connection->getQueryBuilder();
+			$qb->insert('preview_locations')
+				->values([
+					'bucket' => $qb->createNamedParameter('preview-' . $bucket),
+					'object_store' => $qb->createNamedParameter('default'),
+				]);
+			$locationId = $qb->executeStatement();
+		}
+		$preview = new Preview();
+		$preview->setFileId($fileId);
+		$preview->setCrop(true);
+		$preview->setIsMax(true);
+		$preview->setWidth(100);
+		$preview->setHeight(100);
+		$preview->setSize(100);
+		$preview->setMtime(time());
+		$preview->setMimetype(IPreview::MIMETYPE_PNG);
+		$preview->setEtag("abcdefg");
+
+		if ($locationId) {
+			$preview->setLocationId($locationId);
+		}
+		$this->previewMapper->insert($preview);
+	}
+}