diff --git a/lib/private/DB/QueryBuilder/QueryBuilder.php b/lib/private/DB/QueryBuilder/QueryBuilder.php
index 3b1c48306a678..338e66ea7c5a9 100644
--- a/lib/private/DB/QueryBuilder/QueryBuilder.php
+++ b/lib/private/DB/QueryBuilder/QueryBuilder.php
@@ -1353,4 +1353,21 @@ public function quoteAlias($alias) {
 
 		return $this->helper->quoteColumnName($alias);
 	}
+
+	/**
+	 * Either appends to or replaces a single, generic query part.
+	 *
+	 * The available parts are: 'select', 'from', 'set', 'where',
+	 * 'groupBy', 'having' and 'orderBy'.
+	 *
+	 * @param string $sqlPartName
+	 * @param mixed  $sqlPart
+	 * @param bool   $append
+	 *
+	 * @return $this This QueryBuilder instance.
+	 */
+	public function add(string $sqlPartName, $sqlPart, bool $append = false) {
+		$this->queryBuilder->add($sqlPartName, $sqlPart, $append);
+		return $this;
+	}
 }
diff --git a/lib/private/Files/Cache/CacheQueryBuilder.php b/lib/private/Files/Cache/CacheQueryBuilder.php
index 774691ebc3189..f10080768d011 100644
--- a/lib/private/Files/Cache/CacheQueryBuilder.php
+++ b/lib/private/Files/Cache/CacheQueryBuilder.php
@@ -25,6 +25,7 @@
  */
 namespace OC\Files\Cache;
 
+use Doctrine\DBAL\Platforms\MySQLPlatform;
 use OC\DB\QueryBuilder\QueryBuilder;
 use OC\SystemConfig;
 use OCP\DB\QueryBuilder\IQueryBuilder;
@@ -41,12 +42,24 @@ public function __construct(IDBConnection $connection, SystemConfig $systemConfi
 		parent::__construct($connection, $systemConfig, $logger);
 	}
 
-	public function selectFileCache(string $alias = null) {
+	public function selectFileCache(string $alias = null, string $mysqlIndexHint = '') {
 		$name = $alias ? $alias : 'filecache';
 		$this->select("$name.fileid", 'storage', 'path', 'path_hash', "$name.parent", 'name', 'mimetype', 'mimepart', 'size', 'mtime',
 			'storage_mtime', 'encrypted', 'etag', 'permissions', 'checksum', 'metadata_etag', 'creation_time', 'upload_time')
-			->from('filecache', $name)
-			->leftJoin($name, 'filecache_extended', 'fe', $this->expr()->eq("$name.fileid", 'fe.fileid'));
+			->from('filecache', $name);
+		if ($mysqlIndexHint !== '' && $this->getConnection()->getDatabasePlatform() instanceof MySQLPlatform) {
+			$this->add('join', [
+				$this->quoteAlias($name) => [
+					// horrible query builder crimes to sneak in raw sql after the "FROM oc_filecache $name"
+					'joinType' => $mysqlIndexHint . ' left',
+					'joinTable' => $this->getTableName('filecache_extended'),
+					'joinAlias' => $this->quoteAlias('fe'),
+					'joinCondition' => $this->expr()->eq("$name.fileid", 'fe.fileid'),
+				],
+			], true);
+		} else {
+			$this->leftJoin($name, 'filecache_extended', 'fe', $this->expr()->eq("$name.fileid", 'fe.fileid'));
+		}
 
 		$this->alias = $name;
 
diff --git a/lib/private/Files/Cache/QuerySearchHelper.php b/lib/private/Files/Cache/QuerySearchHelper.php
index e065e95e4fd22..c3e6d91b28206 100644
--- a/lib/private/Files/Cache/QuerySearchHelper.php
+++ b/lib/private/Files/Cache/QuerySearchHelper.php
@@ -103,7 +103,13 @@ public function searchInCaches(ISearchQuery $searchQuery, array $caches): array
 
 		$builder = $this->getQueryBuilder();
 
-		$query = $builder->selectFileCache('file');
+		// mysql really likes to pick an index for sorting if it can't fully satisfy the where
+		// filter with an index, since search queries pretty much never are fully filtered by index
+		// mysql often picks an index for sorting instead of the *much* more useful index for filtering.
+		//
+		// To bypass this, we tell mysql explicitly not to use the mtime (the default order field) index,
+		// so it will instead pick an index that is actually useful.
+		$query = $builder->selectFileCache('file', 'ignore index for order by (fs_mtime)');
 
 		if ($this->searchBuilder->shouldJoinTags($searchQuery->getSearchOperation())) {
 			$user = $searchQuery->getUser();