#179143 by chx and agentrickard: unify update code for files, fixing postgresql bugs with it

modules/system/system.install

@@ -4221,20 +4221,8 @@ function system_update_6022() {
   db_add_index($ret, 'upload', 'vid', array('vid'));
 
   // The nid column was renamed to uid. Use the old nid to find the node's uid.
-  switch ($GLOBALS['db_type']) {
-    case 'mysql':
-    case 'mysqli':
-      $ret[] = update_sql('UPDATE {files} f JOIN {node} n ON f.uid = n.nid SET f.uid = n.uid');
-      // Use the existing vid to find the nid.
-      $ret[] = update_sql('UPDATE {upload} u JOIN {node_revisions} r ON u.vid = r.vid SET u.nid = r.nid');
-      break;
-
-    case 'pgsql':
-      $ret[] = update_sql('UPDATE {files} AS f SET uid = n.uid FROM {node} n WHERE f.uid=n.nid');
-      // Use the existing vid to find the nid.
-      $ret[] = update_sql('UPDATE {upload} AS u SET nid = r.nid FROM {node_revisions} r WHERE u.vid = r.vid');
-      break;
-  }
+  update_sql('UPDATE {files} SET uid = (SELECT n.uid FROM {node} n WHERE {files}.uid = n.nid)');
+  update_sql('UPDATE {upload} SET nid = (SELECT r.nid FROM {node_revisions} r WHERE {upload}.vid = r.vid)');
 
   // Mark all existing files as FILE_STATUS_PERMANENT.
   $ret[] = update_sql('UPDATE {files} SET status = 1');