Fix UniqueConstraintViolationException while insert into oc_filecache

* fixes #6160 by not being prone to the race condition in insertIfNotExists
* fixes #12228 by not using a query that can result in a deadlock
* replaces the insertIfNotExists call with an insert which is wrapped into a try-catch block

Signed-off-by: Morris Jobke <hey@morrisjobke.de>

lib/private/Files/Cache/Cache.php

@@ -37,6 +37,7 @@
 
 namespace OC\Files\Cache;
 
+use Doctrine\DBAL\Exception\UniqueConstraintViolationException;
 use OCP\DB\QueryBuilder\IQueryBuilder;
 use Doctrine\DBAL\Driver\Statement;
 use OCP\Files\Cache\ICache;
@@ -268,12 +269,20 @@ public function insert($file, array $data) {
 			return trim($item, "`");
 		}, $queryParts);
 		$values = array_combine($queryParts, $params);
-		if (\OC::$server->getDatabaseConnection()->insertIfNotExist('*PREFIX*filecache', $values, [
-			'storage',
-			'path_hash',
-		])
-		) {
-			return (int)$this->connection->lastInsertId('*PREFIX*filecache');
+
+		try {
+			$builder = $this->connection->getQueryBuilder();
+			$builder->insert('filecache');
+
+			foreach ($values as $column => $value) {
+				$builder->setValue($column, $builder->createNamedParameter($value));
+			}
+
+			if ($builder->execute()) {
+				return (int)$this->connection->lastInsertId('*PREFIX*filecache');
+			}
+		} catch(UniqueConstraintViolationException $e) {
+			// entry exists already
 		}
 
 		// The file was created in the mean time