Reduced DB contention in User::saveOptions().

Change-Id: Ic91501cd6476dae54b54b85f2f06c25bd2577c9b

diff --git a/includes/User.php b/includes/User.php
index ed97deb..eda8bc9 100644 (file)
--- a/includes/User.php
+++ b/includes/User.php
@@ -4428,8 +4428,18 @@ class User {
                }
 
                $dbw = wfGetDB( DB_MASTER );
-               $dbw->delete( 'user_properties', array( 'up_user' => $userId ), __METHOD__ );
-               $dbw->insert( 'user_properties', $insert_rows, __METHOD__ );
+               $hasRows = $dbw->selectField( 'user_properties', '1',
+                       array( 'up_user' => $userId ), __METHOD__ );
+
+               if ( $hasRows ) {
+                       // Only do this delete if there is something there. A very large portion of
+                       // calls to this function are for setting 'rememberpassword' for new accounts.
+                       // Doing this delete for new accounts with no rows in the table rougly causes
+                       // gap locks on [max user ID,+infinity) which causes high contention since many
+                       // updates will pile up on each other since they are for higher (newer) user IDs.
+                       $dbw->delete( 'user_properties', array( 'up_user' => $userId ), __METHOD__ );
+               }
+               $dbw->insert( 'user_properties', $insert_rows, __METHOD__, array( 'IGNORE' ) );
        }
 
        /**