Index: includes/path.inc
===================================================================
RCS file: /cvs/drupal/drupal/includes/path.inc,v
retrieving revision 1.36
diff -u -p -r1.36 path.inc
--- includes/path.inc	16 May 2009 19:07:02 -0000	1.36
+++ includes/path.inc	18 May 2009 23:09:35 -0000
@@ -50,6 +50,7 @@ function drupal_lookup_path($action, $pa
   $no_src = &drupal_static(__FUNCTION__ . ':no_src', array());
   $count = &drupal_static(__FUNCTION__ . ':count');
   $system_paths = &drupal_static(__FUNCTION__ . ':system_paths');
+  $whitelist = &drupal_static(__FUNCTION__ . ':whitelist');
   $no_aliases = &drupal_static(__FUNCTION__ . ':no_alias', array());
   $first_call = &drupal_static(__FUNCTION__ . ':first_call', TRUE);
 
@@ -70,9 +71,11 @@ function drupal_lookup_path($action, $pa
   elseif ($count > 0 && $path != '') {
     if ($action == 'alias') {
       // During the first call to drupal_lookup_path() per language, load the
-      // expected system paths for the page from cache.
+      // expected system paths for the page from cache and fetch the path
+      // whitelist variable.
       if ($first_call) {
         $first_call = FALSE;
+        $whitelist = variable_get('path_optimization_list', drupal_path_whitelist());
         $map[$path_language] = array();
         // Load system paths from cache.
         $cid = current_path();
@@ -93,9 +96,13 @@ function drupal_lookup_path($action, $pa
       if (isset($map[$path_language][$path])) {
         return $map[$path_language][$path];
       }
+      // If the alias is in the whitelist, return FALSE.
+      if (!drupal_match_path($path, $whitelist)) {
+        return FALSE;
+      }
       // For system paths which were not cached, query aliases individually.
-      else if (!isset($no_aliases[$path_language][$path])) {
-        // Get the most fitting result falling back with alias without language
+      if (!isset($no_aliases[$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(
           ':src' => $path,
           ':language' => $path_language
@@ -347,3 +354,19 @@ function drupal_match_path($path, $patte
 function current_path() {
   return $_GET['q'];
 }
+
+/**
+ * Helper function for drupal_lookup_path().
+ *
+ * @return
+ *  A list of system paths to be used as the default whitelist for
+ *  drupal_lookup_path(). Aliases will only be saved or looked up for system
+ *  paths matching this list.
+ *
+ */
+function drupal_path_whitelist() {
+  return 'node*
+  user*
+  taxonomy/term/*';
+}
+
Index: modules/path/path.admin.inc
===================================================================
RCS file: /cvs/drupal/drupal/modules/path/path.admin.inc,v
retrieving revision 1.21
diff -u -p -r1.21 path.admin.inc
--- modules/path/path.admin.inc	16 May 2009 15:23:16 -0000	1.21
+++ modules/path/path.admin.inc	18 May 2009 23:09:37 -0000
@@ -140,6 +140,13 @@ function path_admin_form_validate($form,
   $src = $form_state['values']['src'];
   $dst = $form_state['values']['dst'];
   $pid = isset($form_state['values']['pid']) ? $form_state['values']['pid'] : 0;
+  $whitelist = variable_get('path_optimization_list', drupal_path_whitelist());
+
+  if (!drupal_match_path($src, $whitelist)) {
+    // @TODO Offer a pointer on how to correct this.
+    form_set_error('src', t("The path '@link_path' cannot be aliased because it is skipped by default when querying path aliases.", array('@link_path' => $src)));
+  }
+
   // Language is only set if locale module is enabled, otherwise save for all languages.
   $language = isset($form_state['values']['language']) ? $form_state['values']['language'] : '';
 
Index: sites/default/default.settings.php
===================================================================
RCS file: /cvs/drupal/drupal/sites/default/default.settings.php,v
retrieving revision 1.24
diff -u -p -r1.24 default.settings.php
--- sites/default/default.settings.php	24 Apr 2009 08:16:56 -0000	1.24
+++ sites/default/default.settings.php	18 May 2009 23:09:37 -0000
@@ -330,3 +330,16 @@ $conf = array(
 # $conf['blocked_ips'] = array(
 #   'a.b.c.d',
 # );
+
+/**
+ * drupal_lookup_path() whitelist.
+ *
+ * By default, drupal_lookup_path() only queries path aliases for the paths
+ * defined by drupal_path_blacklist(). If you need to override this list, either
+ * to add or remove paths, you should uncomment the following lines to define
+ * your own string of paths to ignore. An empty value will result in all paths being
+ * queried and may incur a performance penalty
+ */
+# $conf['path_optimizaton_list'] = 'node*
+# user*
+# taxonomy/term/*';
? sites/all/modules/pqp/d7.patch