--- /dev/null
+<?php
+
+namespace Drupal\search\Plugin;
+
+/**
+ * Defines an optional interface for SearchPlugin objects using an index.
+ *
+ * Plugins implementing this interface will have these methods invoked during
+ * search_cron() and via the search module administration form. Plugins not
+ * implementing this interface are assumed to be using their own methods for
+ * searching, not involving separate index tables.
+ *
+ * The user interface for managing search pages displays the indexing status for
+ * search pages implementing this interface. It also allows users to configure
+ * default settings for indexing, and refers to the "default search index". If
+ * your search page plugin uses its own indexing mechanism instead of the
+ * default search index, or overrides the default indexing settings, you should
+ * make this clear on the settings page or other documentation for your plugin.
+ *
+ * Multiple search pages can be created for each search plugin, so you will need
+ * to choose whether these search pages should share an index (in which case
+ * they must not use any search page-specific configuration while indexing) or
+ * they will have separate indexes (which will use additional server resources).
+ */
+interface SearchIndexingInterface {
+
+ /**
+ * Updates the search index for this plugin.
+ *
+ * This method is called every cron run if the plugin has been set as
+ * an active search module on the Search settings page
+ * (admin/config/search/pages). It allows your module to add items to the
+ * built-in search index using search_index(), or to add them to your module's
+ * own indexing mechanism.
+ *
+ * When implementing this method, your module should index content items that
+ * were modified or added since the last run. There is a time limit for cron,
+ * so it is advisable to limit how many items you index per run using
+ * config('search.settings')->get('index.cron_limit') or with your own
+ * setting. And since the cron run could time out and abort in the middle of
+ * your run, you should update any needed internal bookkeeping on when items
+ * have last been indexed as you go rather than waiting to the end of
+ * indexing.
+ */
+ public function updateIndex();
+
+ /**
+ * Clears the search index for this plugin.
+ *
+ * When a request is made to clear all items from the search index related to
+ * this plugin, this method will be called. If this plugin uses the default
+ * search index, this method can call search_index_clear($type) to remove
+ * indexed items from the search database.
+ *
+ * @see search_index_clear()
+ */
+ public function indexClear();
+
+ /**
+ * Marks the search index for reindexing for this plugin.
+ *
+ * When a request is made to mark all items from the search index related to
+ * this plugin for reindexing, this method will be called. If this plugin uses
+ * the default search index, this method can call
+ * search_mark_for_reindex($type) to mark the items in the search database for
+ * reindexing.
+ *
+ * @see search_mark_for_reindex()
+ */
+ public function markForReindex();
+
+ /**
+ * Reports the status of indexing.
+ *
+ * The core search module only invokes this method on active module plugins.
+ * Implementing modules do not need to check whether they are active when
+ * calculating their return values.
+ *
+ * @return array
+ * An associative array with the key-value pairs:
+ * - remaining: The number of items left to index.
+ * - total: The total number of items to index.
+ */
+ public function indexStatus();
+
+}