Further optimize User::saveOptions() by doing deletes by PRIMARY KEY

* We do not care about gap locks here, just as in the case
  with new users. Races should be rare and are simply FWW.

Change-Id: Ie483a2d5df501619acbd868bf894dfc6c911a753

diff --git a/includes/User.php b/includes/User.php
index e728323..6d9f372 100644 (file)
--- a/includes/User.php
+++ b/includes/User.php
@@ -4736,28 +4736,35 @@ class User {
                        // Don't bother storing default values
                        $defaultOption = self::getDefaultOption( $key );
                        if ( ( is_null( $defaultOption ) &&
-                                       !( $value === false || is_null( $value ) ) ) ||
-                                       $value != $defaultOption ) {
+                               !( $value === false || is_null( $value ) ) ) ||
+                               $value != $defaultOption
+                       ) {
                                $insert_rows[] = array(
-                                               'up_user' => $userId,
-                                               'up_property' => $key,
-                                               'up_value' => $value,
-                                       );
+                                       'up_user' => $userId,
+                                       'up_property' => $key,
+                                       'up_value' => $value,
+                               );
                        }
                }
 
                $dbw = wfGetDB( DB_MASTER );
-               $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
+               // Find and delete any prior preference rows...
+               $res = $dbw->select( 'user_properties',
+                       array( 'up_property' ), array( 'up_user' => $userId ), __METHOD__ );
+               $priorKeys = array();
+               foreach ( $res as $row ) {
+                       $priorKeys[] = $row->up_property;
+               }
+               if ( count( $priorKeys ) ) {
+                       // Do the DELETE by PRIMARY KEY for prior rows. 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__ );
+                       // Doing a blanket per-user DELETE for new accounts with no rows in the table
+                       // causes gap locks on [max user ID,+infinity) which causes high contention since
+                       // updates will pile up on each other as they are for higher (newer) user IDs.
+                       $dbw->delete( 'user_properties',
+                               array( 'up_user' => $userId, 'up_property' => $priorKeys ), __METHOD__ );
                }
+               // Insert the new preference rows
                $dbw->insert( 'user_properties', $insert_rows, __METHOD__, array( 'IGNORE' ) );
        }