Optimize header fetching of multi-folder searches with natural (UID) sorting

program/lib/Roundcube/rcube_imap.php

@@ -955,6 +955,14 @@ class rcube_imap extends rcube_storage
             $sort_field = $this->sort_field;
             $search_set = $this->search_set;
 
+            // prepare paging
+            $cnt   = $search_set->count();
+            $from  = ($page-1) * $page_size;
+            $to    = $from + $page_size;
+            $slice_length = min($page_size, $cnt - $from);
+
+            // fetch resultset headers, sort and slice them
+            if (!empty($sort_field)) {
                 $this->sort_field = null;
                 $this->page_size = 1000;  // fetch up to 1000 matching messages per folder
                 $this->threading = false;
@@ -968,13 +976,8 @@ class rcube_imap extends rcube_storage
                     }
                 }
 
-            // do sorting and paging
-            $cnt   = $search_set->count();
-            $from  = ($page-1) * $page_size;
-            $to    = $from + $page_size;
-
                 // sort headers
-            if (!$this->threading && !empty($a_msg_headers)) {
+                if (!empty($a_msg_headers)) {
                     $a_msg_headers = $this->conn->sortHeaders($a_msg_headers, $sort_field, $this->sort_order);
                 }
 
@@ -982,8 +985,22 @@ class rcube_imap extends rcube_storage
                 $search_set->set_message_index($a_msg_headers, $sort_field, $this->sort_order);
 
                 // only return the requested part of the set
-            $slice_length  = min($page_size, $cnt - $from);
                 $a_msg_headers = array_slice(array_values($a_msg_headers), $from, $slice_length);
+            }
+            else {
+                // slice resultset first...
+                $fetch = array();
+                foreach (array_slice($search_set->get(), $from, $slice_length) as $msg_id) {
+                    list($uid, $folder) = explode('-', $msg_id, 2);
+                    $fetch[$folder][] = $uid;
+                }
+
+                // ... and fetch the requested set of headers
+                $a_msg_headers = array();
+                foreach ($fetch as $folder => $a_index) {
+                    $a_msg_headers = array_merge($a_msg_headers, array_values($this->fetch_headers($folder, $a_index)));
+                }
+            }
 
             if ($slice) {
                 $a_msg_headers = array_slice($a_msg_headers, -$slice, $slice);

program/lib/Roundcube/rcube_result_multifolder.php

@@ -168,6 +168,21 @@ class rcube_result_multifolder
         }
     }
 
+    /**
+     * Slices data set.
+     *
+     * @param $offset Offset (as for PHP's array_slice())
+     * @param $length Number of elements (as for PHP's array_slice())
+     *
+     */
+    public function slice($offset, $length)
+    {
+        $data = array_slice($this->get(), $offset, $length);
+
+        $this->index = $data;
+        $this->meta['count'] = count($data);
+    }
+
     /**
      * Filters data set. Removes elements not listed in $ids list.
      *

program/steps/mail/search.inc

@@ -108,7 +108,8 @@ if (!empty($subject)) {
 
     // search all, current or subfolders folders
     if ($scope == 'all') {
-        $mboxes = $RCMAIL->storage->list_folders_subscribed('', '*', 'mail');
+        $mboxes = $RCMAIL->storage->list_folders_subscribed('', '*', 'mail', null, true);
+        natcasesort($mboxes);  // we want natural alphabetic sorting of folders in the result set
     }
     else if ($scope == 'sub') {
         $mboxes = $RCMAIL->storage->list_folders_subscribed($mbox, '*', 'mail');