feat(scanner): enable use of a setting to disable DB transaction

while doing a files scan from storage, we may want not to use DB transactions

enable the use of a setting for that

define filescanner_no_transactions in system config to enable this (i.e. in config.php)

Signed-off-by: Matthieu Gallien <matthieu.gallien@nextcloud.com>
Signed-off-by: Louis Chmn <louis@chmn.me>

lib/private/Files/Cache/Scanner.php

@@ -19,6 +19,7 @@ use OCP\Files\Storage\IReliableEtagStorage;
 use OCP\IConfig;
 use OCP\IDBConnection;
 use OCP\Lock\ILockingProvider;
+use OC\Lock\DBLockingProvider;
 use OCP\Server;
 use Psr\Log\LoggerInterface;
 
@@ -70,9 +71,10 @@ class Scanner extends BasicEmitter implements IScanner {
 		$this->storage = $storage;
 		$this->storageId = $this->storage->getId();
 		$this->cache = $storage->getCache();
+		/** @var IConfig $config */
 		$config = Server::get(IConfig::class);
 		$this->cacheActive = !$config->getSystemValueBool('filesystem_cache_readonly', false);
-		$this->useTransactions = !$config->getSystemValueBool('filescanner_no_transactions', false);
+		$this->useTransactions = !(Server::get(ILockingProvider::class) instanceof DBLockingProvider) && !$config->getSystemValueBool('filescanner_no_transactions', false);
 		$this->lockingProvider = Server::get(ILockingProvider::class);
 		$this->connection = Server::get(IDBConnection::class);
 	}

lib/private/Files/Utils/Scanner.php

@@ -27,9 +27,11 @@ use OCP\Files\Mount\IMountPoint;
 use OCP\Files\NotFoundException;
 use OCP\Files\Storage\IStorage;
 use OCP\Files\StorageNotAvailableException;
+use OCP\IConfig;
 use OCP\IDBConnection;
 use OCP\Lock\ILockingProvider;
 use OCP\Lock\LockedException;
+use OCP\Server;
 use Psr\Log\LoggerInterface;
 
 /**
@@ -79,8 +81,10 @@ class Scanner extends PublicEmitter {
 		$this->db = $db;
 		$this->dispatcher = $dispatcher;
 		$this->logger = $logger;
+		/** @var IConfig $config */
+		$config = Server::get(IConfig::class);
 		// when DB locking is used, no DB transactions will be used
-		$this->useTransaction = !(\OC::$server->get(ILockingProvider::class) instanceof DBLockingProvider);
+		$this->useTransaction = !(Server::get(ILockingProvider::class) instanceof DBLockingProvider) && !$config->getSystemValueBool('filescanner_no_transactions', false);
 	}
 
 	/**