silverstripe-fulltextsearch/code/search/SearchVariantSiteTreeSubsitesPolyhome.php

<?php

class SearchVariantSiteTreeSubsitesPolyhome extends SearchVariant {

	function appliesTo($class, $includeSubclasses) {
		return SearchIntrospection::has_extension($class, 'SiteTreeSubsitesPolyhome', $includeSubclasses);
	}

	function currentState() {
		 return Subsite::currentSubsiteID();
	}
	function reindexStates() {
		static $ids = null;

		if ($ids === null) {
			$ids = array(0);
			foreach (DataObject::get('Subsite') as $subsite) $ids[] = $subsite->ID;
		}

		return $ids;
	}
	function activateState($state) {
		if (Controller::has_curr()) {
			Subsite::changeSubsite($state);
		}
		else {
			// TODO: This is a nasty hack - calling Subsite::changeSubsite after request ends
			// throws error because no current controller to access session on
			$_REQUEST['SubsiteID'] = $state;
		}
	}

	function alterDefinition($base, $index) {
		$self = get_class($this);
		
		$index->filterFields['_subsite'] = array(
			'name' => '_subsite',
			'field' => '_subsite',
			'fullfield' => '_subsite',
			'base' => $base,
			'origin' => $base,
			'type' => 'Int',
			'lookup_chain' => array(array('call' => 'variant', 'variant' => $self, 'method' => 'currentState'))
		);
	}

	function alterQuery($query, $index) {
		$subsite = Subsite::currentSubsiteID();
		$query->filter('_subsite', array($subsite, SearchQuery::$missing));
	}

	static $subsites = null;

	/**
	 * We need _really_ complicated logic to find just the changed subsites (because we use versions there's no explicit
	 * deletes, just new versions with different members) so just always use all of them
	 */
	function extractManipulationWriteState(&$writes) {
		$self = get_class($this);

		foreach ($writes as $key => $write) {
			if (!$this->appliesTo($write['class'], true)) continue;

			if (self::$subsites === null) {
				$query = new SQLQuery('ID', 'Subsite');
				self::$subsites = array_merge(array('0'), $query->execute()->column());
			}

			$next = array();

			foreach ($write['statefulids'] as $i => $statefulid) {
				foreach (self::$subsites as $subsiteID) {
					$next[] = array('id' => $statefulid['id'], 'state' => array_merge($statefulid['state'], array($self => $subsiteID)));
				}
			}

			$writes[$key]['statefulids'] = $next;
		}
	}

}