fix(UserMountCache): Set transaction isolation level to REPEATABLE_READ before executing insertIfNotExist without unique index

Signed-off-by: provokateurin <kate@provokateurin.de>

Author: provokateurin

lib/private/Files/Config/UserMountCache.php

@@ -7,6 +7,8 @@
  */
 namespace OC\Files\Config;
 
+use Doctrine\DBAL\Connections\PrimaryReadReplicaConnection;
+use Doctrine\DBAL\TransactionIsolationLevel;
 use OC\User\LazyUser;
 use OCP\Cache\CappedMemoryCache;
 use OCP\DB\QueryBuilder\IQueryBuilder;
@@ -99,6 +101,11 @@ public function registerMounts(IUser $user, array $mounts, ?array $mountProvider
 		$changedMounts = $this->findChangedMounts($newMounts, $cachedMounts);
 
 		if ($addedMounts || $removedMounts || $changedMounts) {
+			$isPrimary = $this->connection instanceof PrimaryReadReplicaConnection && $this->connection->isConnectedToPrimary();
+			if ($isPrimary) {
+				$this->connection->setTransactionIsolation(TransactionIsolationLevel::REPEATABLE_READ);
+			}
+
 			$this->connection->beginTransaction();
 			$userUID = $user->getUID();
 			try {
@@ -124,6 +131,10 @@ public function registerMounts(IUser $user, array $mounts, ?array $mountProvider
 			} catch (\Throwable $e) {
 				$this->connection->rollBack();
 				throw $e;
+			} finally {
+				if ($isPrimary) {
+					$this->connection->setTransactionIsolation(TransactionIsolationLevel::READ_COMMITTED);
+				}
 			}
 
 			// Only fire events after all mounts have already been adjusted in the database.