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[stable33] perf(preview): bulk process preview regeneration #59234

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295 changes: 226 additions & 69 deletions lib/private/Preview/Storage/LocalPreviewStorage.php
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Original file line number Diff line number Diff line change
Expand Up @@ -16,6 +16,7 @@
use OC\Preview\Db\Preview;
use OC\Preview\Db\PreviewMapper;
use OCP\DB\Exception;
use OCP\DB\QueryBuilder\IQueryBuilder;
use OCP\Files\IMimeTypeDetector;
use OCP\Files\IMimeTypeLoader;
use OCP\Files\IRootFolder;
Expand All @@ -30,6 +31,8 @@
use RecursiveIteratorIterator;

class LocalPreviewStorage implements IPreviewStorage {
private const SCAN_BATCH_SIZE = 1000;

public function __construct(
private readonly IConfig $config,
private readonly PreviewMapper $previewMapper,
Expand Down Expand Up @@ -117,88 +120,241 @@ public function scan(): int {
if (!file_exists($this->getPreviewRootFolder())) {
return 0;
}

$scanner = new RecursiveDirectoryIterator($this->getPreviewRootFolder());
$previewsFound = 0;
$skipFiles = [];

/**
* Use an associative array keyed by path for O(1) lookup instead of
* the O(n) in_array() the original code used.
*
* @var array<string, true> $skipPaths
*/
$skipPaths = [];

/**
* Pending previews grouped by fileId. A single original file can have
* many preview variants (different sizes/formats), so we group them to
* issue one filecache lookup per original file rather than one per
* preview variant.
*
* @var array<int, list<array{preview: Preview, filePath: string, realPath: string}>> $pendingByFileId
*/
$pendingByFileId = [];

/**
* path_hash => realPath for legacy filecache entries that need to be
* cleaned up. Only populated when $checkForFileCache is true.
*
* @var array<string, string> $pendingPathHashes
*/
$pendingPathHashes = [];
$pendingCount = 0;

foreach (new RecursiveIteratorIterator($scanner) as $file) {
if ($file->isFile() && !in_array((string)$file, $skipFiles, true)) {
$preview = Preview::fromPath((string)$file, $this->mimeTypeDetector);
if ($preview === false) {
$this->logger->error('Unable to parse preview information for ' . $file->getRealPath());
continue;
}
if (!$file->isFile()) {
continue;
}

$filePath = $file->getPathname();
if (isset($skipPaths[$filePath])) {
continue;
}

$preview = Preview::fromPath($filePath, $this->mimeTypeDetector);
if ($preview === false) {
$this->logger->error('Unable to parse preview information for ' . $file->getRealPath());
continue;
}

$preview->setSize($file->getSize());
$preview->setMtime($file->getMtime());
$preview->setEncrypted(false);

$realPath = $file->getRealPath();
$pendingByFileId[$preview->getFileId()][] = [
'preview' => $preview,
'filePath' => $filePath,
'realPath' => $realPath,
];
$pendingCount++;

if ($checkForFileCache) {
$relativePath = str_replace($this->getRootFolder() . '/', '', $realPath);
$pendingPathHashes[md5($relativePath)] = $realPath;
}

if ($pendingCount >= self::SCAN_BATCH_SIZE) {
$this->connection->beginTransaction();
try {
$preview->setSize($file->getSize());
$preview->setMtime($file->getMtime());
$preview->setEncrypted(false);

$qb = $this->connection->getQueryBuilder();
$result = $qb->select('storage', 'etag', 'mimetype')
->from('filecache')
->where($qb->expr()->eq('fileid', $qb->createNamedParameter($preview->getFileId())))
->setMaxResults(1)
->runAcrossAllShards() // Unavoidable because we can't extract the storage_id from the preview name
->executeQuery()
->fetchAssociative();

if ($result === false) {
// original file is deleted
$this->logger->warning('Original file ' . $preview->getFileId() . ' was not found. Deleting preview at ' . $file->getRealPath());
@unlink($file->getRealPath());
continue;
}
$previewsFound += $this->processScanBatch($pendingByFileId, $pendingPathHashes, $checkForFileCache, $skipPaths);
$this->connection->commit();
} catch (\Exception $e) {
$this->connection->rollBack();
$this->logger->error($e->getMessage(), ['exception' => $e]);
throw $e;
}
$pendingByFileId = [];
$pendingPathHashes = [];
$pendingCount = 0;
}
}

if ($pendingCount > 0) {
$this->connection->beginTransaction();
try {
$previewsFound += $this->processScanBatch($pendingByFileId, $pendingPathHashes, $checkForFileCache, $skipPaths);
$this->connection->commit();
} catch (\Exception $e) {
$this->connection->rollBack();
$this->logger->error($e->getMessage(), ['exception' => $e]);
throw $e;
}
}

return $previewsFound;
}

/**
* Process one batch of preview files collected during scan().
*
* @param array<int, list<array{preview: Preview, filePath: string, realPath: string}>> $pendingByFileId
* @param array<string, string> $pendingPathHashes path_hash => realPath
* @param array<string, true> $skipPaths Modified in place: newly-moved paths are added so the outer iterator skips them.
*/
private function processScanBatch(
array $pendingByFileId,
array $pendingPathHashes,
bool $checkForFileCache,
array &$skipPaths,
): int {
$filecacheByFileId = $this->fetchFilecacheByFileIds(array_keys($pendingByFileId));
$legacyByPathHash = [];
if ($checkForFileCache && $pendingPathHashes !== []) {
$legacyByPathHash = $this->fetchFilecacheByPathHashes(array_keys($pendingPathHashes));
}

$previewsFound = 0;
foreach ($pendingByFileId as $fileId => $items) {
if (!isset($filecacheByFileId[$fileId])) {
// Original file has been deleted – clean up all its previews.
foreach ($items as $item) {
$this->logger->warning('Original file ' . $fileId . ' was not found. Deleting preview at ' . $item['realPath']);
@unlink($item['realPath']);
}
continue;
}

$filecacheRow = $filecacheByFileId[$fileId];
foreach ($items as $item) {
$preview = $item['preview'];

if ($checkForFileCache) {
$relativePath = str_replace($this->getRootFolder() . '/', '', $file->getRealPath());
if ($checkForFileCache) {
$relativePath = str_replace($this->getRootFolder() . '/', '', $item['realPath']);
$pathHash = md5($relativePath);
if (isset($legacyByPathHash[$pathHash])) {
$legacyRow = $legacyByPathHash[$pathHash];
$qb = $this->connection->getQueryBuilder();
$result2 = $qb->select('fileid', 'storage', 'etag', 'mimetype', 'parent')
->from('filecache')
->where($qb->expr()->eq('path_hash', $qb->createNamedParameter(md5($relativePath))))
->runAcrossAllShards()
->setMaxResults(1)
->executeQuery()
->fetchAssociative();

if ($result2 !== false) {
$qb->delete('filecache')
->where($qb->expr()->eq('fileid', $qb->createNamedParameter($result2['fileid'])))
->andWhere($qb->expr()->eq('storage', $qb->createNamedParameter($result2['storage'])))
->executeStatement();
$this->deleteParentsFromFileCache((int)$result2['parent'], (int)$result2['storage']);
}
$qb->delete('filecache')
->where($qb->expr()->eq('fileid', $qb->createNamedParameter($legacyRow['fileid'])))
->andWhere($qb->expr()->eq('storage', $qb->createNamedParameter($legacyRow['storage'])))
->executeStatement();
$this->deleteParentsFromFileCache((int)$legacyRow['parent'], (int)$legacyRow['storage']);
}
}

$preview->setStorageId((int)$result['storage']);
$preview->setEtag($result['etag']);
$preview->setSourceMimetype($this->mimeTypeLoader->getMimetypeById((int)$result['mimetype']));
$preview->generateId();
// try to insert, if that fails the preview is already in the DB
$this->previewMapper->insert($preview);
$preview->setStorageId((int)$filecacheRow['storage']);
$preview->setEtag($filecacheRow['etag']);
$preview->setSourceMimetype($this->mimeTypeLoader->getMimetypeById((int)$filecacheRow['mimetype']));
$preview->generateId();

// Move old flat preview to new format
$dirName = str_replace($this->getPreviewRootFolder(), '', $file->getPath());
if (preg_match('/[0-9a-e]\/[0-9a-e]\/[0-9a-e]\/[0-9a-e]\/[0-9a-e]\/[0-9a-e]\/[0-9a-e]\/[0-9]+/', $dirName) !== 1) {
$previewPath = $this->constructPath($preview);
$this->createParentFiles($previewPath);
$ok = rename($file->getRealPath(), $previewPath);
if (!$ok) {
throw new LogicException('Failed to move ' . $file->getRealPath() . ' to ' . $previewPath);
}

$skipFiles[] = $previewPath;
}
$this->connection->beginTransaction();
try {
$this->previewMapper->insert($preview);
$this->connection->commit();
} catch (Exception $e) {
$this->connection->rollBack();
if ($e->getReason() !== Exception::REASON_UNIQUE_CONSTRAINT_VIOLATION) {
throw $e;
}
}

// Move old flat preview to new nested directory format.
$dirName = str_replace($this->getPreviewRootFolder(), '', $item['filePath']);
if (preg_match('/[0-9a-e]\/[0-9a-e]\/[0-9a-e]\/[0-9a-e]\/[0-9a-e]\/[0-9a-e]\/[0-9a-e]\/[0-9]+/', $dirName) !== 1) {
$previewPath = $this->constructPath($preview);
$this->createParentFiles($previewPath);
$ok = rename($item['realPath'], $previewPath);
if (!$ok) {
throw new LogicException('Failed to move ' . $item['realPath'] . ' to ' . $previewPath);
}
// Mark the destination so the outer iterator skips it if it encounters the path later.
$skipPaths[$previewPath] = true;
}

$previewsFound++;
}
}

return $previewsFound;
}

/**
* Bulk-fetch filecache rows for a set of fileIds.
*
* @param int[] $fileIds
*/
private function fetchFilecacheByFileIds(array $fileIds): array {
if (empty($fileIds)) {
return [];
}

$result = [];
$qb = $this->connection->getQueryBuilder();
$qb->select('fileid', 'storage', 'etag', 'mimetype')
->from('filecache');
foreach (array_chunk($fileIds, 1000) as $chunk) {
$qb->andWhere(
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@joshtrichards joshtrichards Mar 29, 2026

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Suggested change
$qb->andWhere(
$qb->orWhere(

Though... I think it'd be more robust if separate queries are merged. Something like this?

foreach (array_chunk($fileIds, 1000) as $chunk) {
    $qb = $this->connection->getQueryBuilder();
    $qb->select('fileid', 'storage', 'etag', 'mimetype')
        ->from('filecache')
        ->where($qb->expr()->in('fileid', $qb->createNamedParameter($chunk, IQueryBuilder::PARAM_INT_ARRAY)));
    $rows = $qb->runAcrossAllShards()->executeQuery();
    while ($row = $rows->fetchAssociative()) {
        $result[(int)$row['fileid']] = $row;
    }
    $rows->closeCursor();
}

Though looking closer, isn't the foreach chunking in this function a no-op at the moment since SCAN_BATCH_SIZE in the caller currently guarantees there will already be <1000? I'd either drop the the misleading chunk support here or fix it properly so it works if >1000 are ever passed.

$qb->expr()->in('fileid', $qb->createNamedParameter($chunk, IQueryBuilder::PARAM_INT_ARRAY))
);
}
$rows = $qb->runAcrossAllShards()
->executeQuery();
while ($row = $rows->fetchAssociative()) {
$result[(int)$row['fileid']] = $row;
}
$rows->closeCursor();
return $result;
}

/**
* Bulk-fetch filecache rows for a set of path_hashes (legacy migration).
*
* @param string[] $pathHashes
*/
private function fetchFilecacheByPathHashes(array $pathHashes): array {
if (empty($pathHashes)) {
return [];
}

$result = [];
$qb = $this->connection->getQueryBuilder();
$qb->select('fileid', 'storage', 'etag', 'mimetype', 'parent', 'path_hash')
->from('filecache');
foreach (array_chunk($pathHashes, 1000) as $chunk) {
$qb->andWhere(
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@joshtrichards joshtrichards Mar 29, 2026

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Suggested change
$qb->andWhere(
$qb->orWhere(

Same commentary as above applies though.

$qb->expr()->in('path_hash', $qb->createNamedParameter($chunk, IQueryBuilder::PARAM_STR_ARRAY))
);
}
$rows = $qb->runAcrossAllShards()
->executeQuery();
while ($row = $rows->fetchAssociative()) {
$result[$row['path_hash']] = $row;
}
$rows->closeCursor();
return $result;
}

/**
* Recursive method that deletes the folder and its parent folders if it's not
* empty.
Expand All @@ -210,10 +366,11 @@ private function deleteParentsFromFileCache(int $folderId, int $storageId): void
->where($qb->expr()->eq('parent', $qb->createNamedParameter($folderId)))
->setMaxResults(1)
->runAcrossAllShards()
->executeQuery()
->fetchAssociative();
->executeQuery();
$row = $result->fetchAssociative();
$result->closeCursor();

if ($result !== false) {
if ($row !== false) {
// there are other files in the directory, don't delete yet
return;
}
Expand All @@ -225,11 +382,11 @@ private function deleteParentsFromFileCache(int $folderId, int $storageId): void
->where($qb->expr()->eq('fileid', $qb->createNamedParameter($folderId)))
->andWhere($qb->expr()->eq('storage', $qb->createNamedParameter($storageId)))
->setMaxResults(1)
->executeQuery()
->fetchAssociative();

if ($result !== false) {
$parentFolderId = (int)$result['parent'];
->executeQuery();
$row = $result->fetchAssociative();
$result->closeCursor();
if ($row !== false) {
$parentFolderId = (int)$row['parent'];

$qb = $this->connection->getQueryBuilder();
$qb->delete('filecache')
Expand Down
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