Fix causal reads in CalDAV backend

Signed-off-by: Christoph Wurst <christoph@winzerhof-wurst.at>

apps/dav/lib/CalDAV/CalDavBackend.php

@@ -64,6 +64,7 @@ use OCA\DAV\Events\CalendarUpdatedEvent;
 use OCA\DAV\Events\SubscriptionCreatedEvent;
 use OCA\DAV\Events\SubscriptionDeletedEvent;
 use OCA\DAV\Events\SubscriptionUpdatedEvent;
+use OCP\AppFramework\Db\TTransactional;
 use OCP\Calendar\Exceptions\CalendarException;
 use OCP\DB\Exception;
 use OCP\DB\QueryBuilder\IQueryBuilder;
@@ -119,6 +120,9 @@ use function time;
  * @package OCA\DAV\CalDAV
  */
 class CalDavBackend extends AbstractBackend implements SyncSupport, SubscriptionSupport, SchedulingSupport {
+
+	use TTransactional;
+
 	public const CALENDAR_TYPE_CALENDAR = 0;
 	public const CALENDAR_TYPE_SUBSCRIPTION = 1;
 
@@ -812,15 +816,19 @@ class CalDavBackend extends AbstractBackend implements SyncSupport, Subscription
 			}
 		}
 
-		$query = $this->db->getQueryBuilder();
-		$query->insert('calendars');
-		foreach ($values as $column => $value) {
-			$query->setValue($column, $query->createNamedParameter($value));
-		}
-		$query->executeStatement();
-		$calendarId = $query->getLastInsertId();
+		[$calendarId, $calendarData] = $this->atomic(function() use ($values) {
+			$query = $this->db->getQueryBuilder();
+			$query->insert('calendars');
+			foreach ($values as $column => $value) {
+				$query->setValue($column, $query->createNamedParameter($value));
+			}
+			$query->executeStatement();
+			$calendarId = $query->getLastInsertId();
+
+			$calendarData = $this->getCalendarById($calendarId);
+			return [$calendarId, $calendarData];
+		}, $this->db);
 
-		$calendarData = $this->getCalendarById($calendarId);
 		$this->dispatcher->dispatchTyped(new CalendarCreatedEvent((int)$calendarId, $calendarData));
 
 		return $calendarId;
@@ -2446,21 +2454,22 @@ class CalDavBackend extends AbstractBackend implements SyncSupport, Subscription
 			}
 		}
 
-		$valuesToInsert = [];
-
-		$query = $this->db->getQueryBuilder();
-
-		foreach (array_keys($values) as $name) {
-			$valuesToInsert[$name] = $query->createNamedParameter($values[$name]);
-		}
+		[$subscriptionId, $subscriptionRow] = $this->atomic(function() use ($values) {
+			$valuesToInsert = [];
+			$query = $this->db->getQueryBuilder();
+			foreach (array_keys($values) as $name) {
+				$valuesToInsert[$name] = $query->createNamedParameter($values[$name]);
+			}
+			$query->insert('calendarsubscriptions')
+				->values($valuesToInsert)
+				->executeStatement();
 
-		$query->insert('calendarsubscriptions')
-			->values($valuesToInsert)
-			->executeStatement();
+			$subscriptionId = $query->getLastInsertId();
 
-		$subscriptionId = $query->getLastInsertId();
+			$subscriptionRow = $this->getSubscriptionById($subscriptionId);
+			return [$subscriptionId, $subscriptionRow];
+		}, $this->db);
 
-		$subscriptionRow = $this->getSubscriptionById($subscriptionId);
 		$this->dispatcher->dispatchTyped(new SubscriptionCreatedEvent($subscriptionId, $subscriptionRow));
 
 		return $subscriptionId;