An example on how to add indexes on silverstripe dataobjects

SiteTreeOptimizationDecorator.php

<?php
class SiteTreeOptimizationDecorator extends DataObjectDecorator {
  public function extraStatics() {
    return array(
      'indexes' => array(
        // Will help when fetching menu's
        'showinmenus_sort' => '(ShowInMenus,Sort)',
        // Will help when fetching a page from sitetree
        'urlsegment_sort' => '(URLSegment,Sort)',
      )
    );
  }
}

WidgetOptimizationDecorator.php

<?php
class WidgetOptimizationDecorator extends DataObjectDecorator {
  public function extraStatics() {
    return array(
      'indexes' => array(
        // Will help when fetching widget
        'parentid_sort' => '(ParentID,Sort)',
      )
    );
  }
}