Index: includes/path.inc
===================================================================
RCS file: /cvs/drupal/drupal/includes/path.inc,v
retrieving revision 1.32
diff -u -p -r1.32 path.inc
--- includes/path.inc	4 Jan 2009 20:04:32 -0000	1.32
+++ includes/path.inc	24 Mar 2009 10:55:04 -0000
@@ -66,7 +66,7 @@ function drupal_lookup_path($action, $pa
         return $map[$path_language][$path];
       }
       // Get the most fitting result falling back with alias without language
-      $alias = db_query("SELECT dst FROM {url_alias} WHERE src = :src AND language IN(:language, '') ORDER BY language DESC", array(
+      $alias = db_query("SELECT dst FROM {url_alias} WHERE src = :src AND language IN(:language, '') ORDER BY language DESC, pid DESC", array(
         ':src' => $path,
         ':language' => $path_language))
         ->fetchField();
@@ -80,7 +80,7 @@ function drupal_lookup_path($action, $pa
       $src = '';
       if (!isset($map[$path_language]) || !($src = array_search($path, $map[$path_language]))) {
         // Get the most fitting result falling back with alias without language
-        if ($src = db_query("SELECT src FROM {url_alias} WHERE dst = :dst AND language IN(:language, '') ORDER BY language DESC", array(
+        if ($src = db_query("SELECT src FROM {url_alias} WHERE dst = :dst AND language IN(:language, '') ORDER BY language DESC, pid DESC", array(
                      ':dst' => $path,
                      ':language' => $path_language))
             ->fetchField()) {
Index: modules/system/system.install
===================================================================
RCS file: /cvs/drupal/drupal/modules/system/system.install,v
retrieving revision 1.312
diff -u -p -r1.312 system.install
--- modules/system/system.install	17 Mar 2009 15:26:29 -0000	1.312
+++ modules/system/system.install	24 Mar 2009 10:55:11 -0000
@@ -1254,11 +1254,11 @@ function system_schema() {
       ),
     ),
     'unique keys' => array(
-      'dst_language' => array('dst', 'language'),
+      'dst_language_pid' => array('dst', 'language', 'pid'),
     ),
     'primary key' => array('pid'),
     'indexes' => array(
-      'src_language' => array('src', 'language'),
+      'src_language_pid' => array('src', 'language', 'pid'),
     ),
   );
 
@@ -3203,11 +3203,15 @@ function system_update_7017() {
 }
 
 /**
- * Replace src index on the {url_alias} table with src, language.
+ * Improve indexes on the {url_alias} table.
+ *
+ * Add language and pid columns to indexes to improve performance.
  */
 function system_update_7018() {
   $ret = array();
-  db_add_index($ret, 'url_alias', 'src_language', array('src', 'language'));
+  db_drop_index($ret, 'url_alias', 'dst_language');
+  db_add_index($ret, 'url_alias', 'dst_language_pid', array('dst', 'language', 'pid'));
+  db_add_index($ret, 'url_alias', 'src_language_pid', array('src', 'language', 'pid'));
   db_drop_index($ret, 'url_alias', 'src');
 
   return $ret;