search: Significantly speed up re-indexing

This significantly speeds up the re-indexing speed for large databases. Since it is
only important to have the system reindexed--and not necessarily what order the
re-indexing happends, the sorting is really just a waste of resources and time.

This dramatically increases the performance of searching for indexable threads, for
instance, from 260900ms to about 42ms.

include/class.search.php

@@ -481,7 +481,7 @@ class MysqlSearchBackend extends SearchBackend {
             LEFT JOIN `".TABLE_PREFIX."_search` A2 ON (A1.`id` = A2.`object_id` AND A2.`object_type`='H')
             WHERE A2.`object_id` IS NULL AND (A1.poster <> 'SYSTEM')
             AND (LENGTH(A1.`title`) + LENGTH(A1.`body`) > 0)
-            ORDER BY A1.`id` DESC LIMIT 500";
+            LIMIT 500";
         if (!($res = db_query_unbuffered($sql, $auto_create)))
             return false;
 
@@ -501,7 +501,7 @@ class MysqlSearchBackend extends SearchBackend {
         $sql = "SELECT A1.`ticket_id` FROM `".TICKET_TABLE."` A1
             LEFT JOIN `".TABLE_PREFIX."_search` A2 ON (A1.`ticket_id` = A2.`object_id` AND A2.`object_type`='T')
             WHERE A2.`object_id` IS NULL
-            ORDER BY A1.`ticket_id` DESC LIMIT 300";
+            LIMIT 300";
         if (!($res = db_query_unbuffered($sql, $auto_create)))
             return false;
 
@@ -524,8 +524,7 @@ class MysqlSearchBackend extends SearchBackend {
 
         $sql = "SELECT A1.`id` FROM `".USER_TABLE."` A1
             LEFT JOIN `".TABLE_PREFIX."_search` A2 ON (A1.`id` = A2.`object_id` AND A2.`object_type`='U')
-            WHERE A2.`object_id` IS NULL
-            ORDER BY A1.`id` DESC";
+            WHERE A2.`object_id` IS NULL";
         if (!($res = db_query_unbuffered($sql, $auto_create)))
             return false;
 
@@ -550,8 +549,7 @@ class MysqlSearchBackend extends SearchBackend {
 
         $sql = "SELECT A1.`id` FROM `".ORGANIZATION_TABLE."` A1
             LEFT JOIN `".TABLE_PREFIX."_search` A2 ON (A1.`id` = A2.`object_id` AND A2.`object_type`='O')
-            WHERE A2.`object_id` IS NULL
-            ORDER BY A1.`id` DESC";
+            WHERE A2.`object_id` IS NULL";
         if (!($res = db_query_unbuffered($sql, $auto_create)))
             return false;
 
@@ -575,8 +573,7 @@ class MysqlSearchBackend extends SearchBackend {
         require_once INCLUDE_DIR . 'class.faq.php';
         $sql = "SELECT A1.`faq_id` FROM `".FAQ_TABLE."` A1
             LEFT JOIN `".TABLE_PREFIX."_search` A2 ON (A1.`faq_id` = A2.`object_id` AND A2.`object_type`='K')
-            WHERE A2.`object_id` IS NULL
-            ORDER BY A1.`faq_id` DESC";
+            WHERE A2.`object_id` IS NULL";
         if (!($res = db_query_unbuffered($sql, $auto_create)))
             return false;