Index: modules/system/system.install
===================================================================
RCS file: /cvs/drupal/drupal/modules/system/system.install,v
retrieving revision 1.490
diff -u -p -r1.490 system.install
--- modules/system/system.install	14 Jul 2010 20:30:09 -0000	1.490
+++ modules/system/system.install	21 Jul 2010 20:46:25 -0000
@@ -1561,11 +1561,9 @@ function system_schema() {
         'default' => '',
       ),
     ),
-    'unique keys' => array(
-      'alias_language' => array('alias', 'language'),
-    ),
     'primary key' => array('pid'),
     'indexes' => array(
+      'alias_language' => array('alias', 'language'),
       'source_language' => array('source', 'language'),
     ),
   );
@@ -2554,7 +2552,7 @@ function system_update_7055() {
 }
 
 /**
- * Remove pid from indexes and unique keys of {url_alias}.
+ * Remove pid from indexes, and replace {url_alias} unique key with an index.
  */
 function system_update_7056() {
   // Drop indexes.
@@ -2562,7 +2560,7 @@ function system_update_7056() {
   db_drop_unique_key('url_alias', 'alias_language_pid');
   // Add indexes back.
   db_add_index('url_alias', 'source_language', array('source', 'language'));
-  db_add_unique_key('url_alias', 'alias_language', array('alias', 'language'));
+  db_add_index('url_alias', 'alias_language', array('alias', 'language'));
 }
 
 /**