tell mysql to ignore the sort index for search queriesbackport/32074/stable22

Signed-off-by: Robin Appelman <robin@icewind.nl>

2 files changed, 12 insertions, 1 deletions

diff --git a/lib/private/DB/QueryBuilder/QueryBuilder.php b/lib/private/DB/QueryBuilder/QueryBuilder.php
index 89265c74fae..bf5ec2f6bec 100644
--- a/lib/private/DB/QueryBuilder/QueryBuilder.php
+++ b/lib/private/DB/QueryBuilder/QueryBuilder.php
@@ -1119,7 +1119,7 @@ class QueryBuilder implements IQueryBuilder {
 	/**
 	 * Adds an ordering to the query results.
 	 *
-	 * @param string $sort The ordering expression.
+	 * @param string|ILiteral|IParameter|IQueryFunction $sort The ordering expression.
 	 * @param string $order The ordering direction.
 	 *
 	 * @return $this This QueryBuilder instance.
diff --git a/lib/private/Files/Cache/SearchBuilder.php b/lib/private/Files/Cache/SearchBuilder.php
index 003d3ac15e7..c8c442bcb8c 100644
--- a/lib/private/Files/Cache/SearchBuilder.php
+++ b/lib/private/Files/Cache/SearchBuilder.php
@@ -232,6 +232,17 @@ class SearchBuilder {
 			if ($field === 'fileid') {
 				$field = 'file.fileid';
 			}
+
+			// Mysql really likes to pick an index for sorting if it can't fully satisfy the where
+			// filter with an index, since search queries pretty much never are fully filtered by index
+			// mysql often picks an index for sorting instead of the much more useful index for filtering.
+			//
+			// By changing the order by to an expression, mysql isn't smart enough to see that it could still
+			// use the index, so it instead picks an index for the filtering
+			if ($field === 'mtime') {
+				$field = $query->func()->add($field, $query->createNamedParameter(0));
+			}
+
 			$query->addOrderBy($field, $order->getDirection());
 		}
 	}