if ( !$dbw->fieldExists( 'recentchanges', 'rc_source' ) ) {
$this->error( 'rc_source field in recentchanges table does not exist.' );
}
if ( !$dbw->fieldExists( 'recentchanges', 'rc_source' ) ) {
$this->error( 'rc_source field in recentchanges table does not exist.' );
}