diff --git a/core/lib/Drupal/Core/Entity/DatabaseStorageControllerNG.php b/core/lib/Drupal/Core/Entity/DatabaseStorageControllerNG.php
index 007d6d3..975dcdc 100644
--- a/core/lib/Drupal/Core/Entity/DatabaseStorageControllerNG.php
+++ b/core/lib/Drupal/Core/Entity/DatabaseStorageControllerNG.php
@@ -235,7 +235,9 @@ protected function invokeHook($hook, EntityInterface $entity) {
   protected function mapToStorageRecord(EntityInterface $entity) {
     $record = new \stdClass();
     foreach ($this->entityInfo['schema_fields_sql']['base table'] as $name) {
-      $record->$name = $entity->$name->value;
+      if (isset($entity->$name->value)) {
+        $record->$name = $entity->$name->value;
+      }
     }
     return $record;
   }
diff --git a/core/modules/aggregator/aggregator.module b/core/modules/aggregator/aggregator.module
index 047026a..20ddec0 100644
--- a/core/modules/aggregator/aggregator.module
+++ b/core/modules/aggregator/aggregator.module
@@ -74,11 +74,11 @@ function aggregator_theme() {
       'template' => 'aggregator-summary-items',
     ),
     'aggregator_summary_item' => array(
-      'variables' => array('item' => NULL),
+      'variables' => array('aggregator_item' => NULL, 'view_mode' => NULL),
       'file' => 'aggregator.pages.inc',
     ),
     'aggregator_item' => array(
-      'variables' => array('item' => NULL),
+      'variables' => array('aggregator_item' => NULL, 'view_mode' => NULL),
       'file' => 'aggregator.pages.inc',
       'template' => 'aggregator-item',
     ),
@@ -94,6 +94,25 @@ function aggregator_theme() {
 }
 
 /**
+ * Implements hook_entity_info().
+ */
+function aggregator_entity_info() {
+  $items['aggregator_item'] = array(
+    'label' => t('Aggregator feed item'),
+    'entity class' => 'Drupal\aggregator\Item',
+    'controller class' => 'Drupal\aggregator\ItemStorageController',
+    'render controller class' => 'Drupal\aggregator\ItemRenderController',
+    'base table' => 'aggregator_item',
+    'fieldable' => TRUE,
+    'entity keys' => array(
+      'id' => 'iid',
+      'label' => 'title',
+    ),
+  );
+  return $items;
+}
+
+/**
  * Implements hook_menu().
  */
 function aggregator_menu() {
@@ -276,7 +295,7 @@ function aggregator_menu() {
  *   An aggregator category title.
  */
 function _aggregator_category_title($category) {
-  return $category['title'];
+  return $category->title;
 }
 
 /**
@@ -516,16 +535,11 @@ function aggregator_save_feed($edit) {
   elseif (!empty($edit['fid'])) {
     $iids = db_query('SELECT iid FROM {aggregator_item} WHERE fid = :fid', array(':fid' => $edit['fid']))->fetchCol();
     if ($iids) {
-      db_delete('aggregator_category_item')
-        ->condition('iid', $iids, 'IN')
-        ->execute();
+      entity_delete_multiple('aggregator_item', $iids);
     }
     db_delete('aggregator_feed')->
       condition('fid', $edit['fid'])
       ->execute();
-    db_delete('aggregator_item')
-      ->condition('fid', $edit['fid'])
-      ->execute();
     // Make sure there is no active block for this feed.
     if (module_exists('block')) {
       db_delete('block')
@@ -717,7 +731,7 @@ function aggregator_feed_load($fid) {
 function aggregator_category_load($cid) {
   $categories = &drupal_static(__FUNCTION__);
   if (!isset($categories[$cid])) {
-    $categories[$cid] = db_query('SELECT * FROM {aggregator_category} WHERE cid = :cid', array(':cid' => $cid))->fetchAssoc();
+    $categories[$cid] = db_query('SELECT * FROM {aggregator_category} WHERE cid = :cid', array(':cid' => $cid))->fetchObject();
   }
 
   return $categories[$cid];
diff --git a/core/modules/aggregator/aggregator.pages.inc b/core/modules/aggregator/aggregator.pages.inc
index 78ca5bc..01db794 100644
--- a/core/modules/aggregator/aggregator.pages.inc
+++ b/core/modules/aggregator/aggregator.pages.inc
@@ -61,7 +61,7 @@ function aggregator_page_source_form($form, $form_state, $feed) {
  * @ingroup forms
  */
 function aggregator_page_category($category) {
-  drupal_add_feed('aggregator/rss/' . $category['cid'], config('system.site')->get('name') . ' ' . t('aggregator - @title', array('@title' => $category['title'])));
+  drupal_add_feed('aggregator/rss/' . $category->cid, config('system.site')->get('name') . ' ' . t('aggregator - @title', array('@title' => $category->title)));
 
   // It is safe to include the cid in the query because it's loaded from the
   // database by aggregator_category_load().
@@ -105,20 +105,17 @@ function aggregator_page_category_form($form, $form_state, $category) {
  * @return
  *   An array of the feed items.
  */
-function aggregator_load_feed_items($type, $data = NULL) {
-  $items = array();
+function aggregator_load_feed_items($type, $data = NULL, $limit = 20) {
   switch ($type) {
     case 'sum':
       $query = db_select('aggregator_item', 'i');
       $query->join('aggregator_feed', 'f', 'i.fid = f.fid');
-      $query->fields('i');
-      $query->addField('f', 'title', 'ftitle');
-      $query->addField('f', 'link', 'flink');
+      $query->fields('i', array('iid'));
       break;
     case 'source':
       $query = db_select('aggregator_item', 'i');
       $query
-        ->fields('i')
+        ->fields('i', array('iid'))
         ->condition('i.fid', $data->fid);
       break;
     case 'category':
@@ -126,25 +123,19 @@ function aggregator_load_feed_items($type, $data = NULL) {
       $query->leftJoin('aggregator_item', 'i', 'c.iid = i.iid');
       $query->leftJoin('aggregator_feed', 'f', 'i.fid = f.fid');
       $query
-        ->fields('i')
-        ->condition('cid', $data['cid']);
-      $query->addField('f', 'title', 'ftitle');
-      $query->addField('f', 'link', 'flink');
+        ->fields('i', array('iid'))
+        ->condition('cid', $data->cid);
       break;
   }
 
   $result = $query
     ->extend('Drupal\Core\Database\Query\PagerSelectExtender')
-    ->limit(20)
+    ->limit($limit)
     ->orderBy('i.timestamp', 'DESC')
     ->orderBy('i.iid', 'DESC')
     ->execute();
 
-  foreach ($result as $item) {
-    $item->categories = db_query('SELECT c.title, c.cid FROM {aggregator_category_item} ci LEFT JOIN {aggregator_category} c ON ci.cid = c.cid WHERE ci.iid = :iid ORDER BY c.title', array(':iid' => $item->iid))->fetchAll();
-    $items[] = $item;
-  }
-
+  $items = entity_load_multiple('aggregator_item', $result->fetchCol());
   return $items;
 }
 
@@ -172,8 +163,9 @@ function _aggregator_page_list($items, $op, $feed_source = '') {
   else {
     // Assemble themed output.
     $output = $feed_source;
-    foreach ($items as $item) {
-      $output .= theme('aggregator_item', array('item' => $item));
+    if ($items) {
+      $rendered_items = entity_view_multiple($items, 'default');
+      $output .= drupal_render($rendered_items);
     }
     $output = theme('aggregator_wrapper', array('content' => $output));
   }
@@ -204,10 +196,10 @@ function aggregator_categorize_items($items, $feed_source = '') {
   $form['categories'] = array(
     '#tree' => TRUE,
   );
+  $form['items'] = entity_view_multiple($items, 'default');
   foreach ($items as $item) {
-    $form['items'][$item->iid] = array('#markup' => theme('aggregator_item', array('item' => $item)));
-    $form['categories'][$item->iid] = array();
-    $categories_result = db_query('SELECT c.cid, c.title, ci.iid FROM {aggregator_category} c LEFT JOIN {aggregator_category_item} ci ON c.cid = ci.cid AND ci.iid = :iid', array(':iid' => $item->iid));
+    $form['categories'][$item->id()] = array();
+    $categories_result = db_query('SELECT c.cid, c.title, ci.iid FROM {aggregator_category} c LEFT JOIN {aggregator_category_item} ci ON c.cid = ci.cid AND ci.iid = :iid', array(':iid' => $item->id()));
     $selected = array();
     foreach ($categories_result as $category) {
       if (!$done) {
@@ -218,7 +210,7 @@ function aggregator_categorize_items($items, $feed_source = '') {
       }
     }
     $done = TRUE;
-    $form['categories'][$item->iid] = array(
+    $form['categories'][$item->id()] = array(
       '#type' => config('aggregator.settings')->get('source.category_selector'),
       '#default_value' => $selected,
       '#options' => $categories,
@@ -319,23 +311,23 @@ function template_preprocess_aggregator_wrapper(&$variables) {
  * @see aggregator-item.tpl.php
  */
 function template_preprocess_aggregator_item(&$variables) {
-  $item = $variables['item'];
+  $item = $variables['aggregator_item'];
 
-  $variables['feed_url'] = check_url($item->link);
-  $variables['feed_title'] = check_plain($item->title);
-  $variables['content'] = aggregator_filter_xss($item->description);
+  $variables['feed_url'] = check_url($item->link->value);
+  $variables['feed_title'] = check_plain($item->title->value);
+  $variables['content'] = aggregator_filter_xss($item->description->value);
 
   $variables['source_url'] = '';
   $variables['source_title'] = '';
-  if (isset($item->ftitle) && isset($item->fid)) {
-    $variables['source_url'] = url("aggregator/sources/$item->fid");
+  if (isset($item->ftitle) && isset($item->fid->value)) {
+    $variables['source_url'] = url("aggregator/sources/$item->fid->value");
     $variables['source_title'] = check_plain($item->ftitle);
   }
-  if (date('Ymd', $item->timestamp) == date('Ymd')) {
-    $variables['source_date'] = t('%ago ago', array('%ago' => format_interval(REQUEST_TIME - $item->timestamp)));
+  if (date('Ymd', $item->timestamp->value) == date('Ymd')) {
+    $variables['source_date'] = t('%ago ago', array('%ago' => format_interval(REQUEST_TIME - $item->timestamp->value)));
   }
   else {
-    $variables['source_date'] = format_date($item->timestamp, 'custom', variable_get('date_format_medium', 'D, m/d/Y - H:i'));
+    $variables['source_date'] = format_date($item->timestamp->value, 'custom', variable_get('date_format_medium', 'D, m/d/Y - H:i'));
   }
 
   $variables['categories'] = array();
@@ -358,9 +350,8 @@ function aggregator_page_sources() {
     $summary_items = array();
     $aggregator_summary_items = config('aggregator.settings')->get('source.list_max');
     if ($aggregator_summary_items) {
-      $items = db_query_range('SELECT i.title, i.timestamp, i.link FROM {aggregator_item} i WHERE i.fid = :fid ORDER BY i.timestamp DESC', 0, $aggregator_summary_items, array(':fid' => $feed->fid));
-      foreach ($items as $item) {
-        $summary_items[] = theme('aggregator_summary_item', array('item' => $item));
+      if ($items = aggregator_load_feed_items('source', $feed, $aggregator_summary_items)) {
+        $summary_items = entity_view_multiple($items, 'summary');
       }
     }
     $feed->url = url('aggregator/sources/' . $feed->fid);
@@ -380,13 +371,12 @@ function aggregator_page_categories() {
   $result = db_query('SELECT c.cid, c.title, c.description FROM {aggregator_category} c LEFT JOIN {aggregator_category_item} ci ON c.cid = ci.cid LEFT JOIN {aggregator_item} i ON ci.iid = i.iid GROUP BY c.cid, c.title, c.description');
 
   $output = '';
+  $summary_items = array();
   foreach ($result as $category) {
     $aggregator_summary_items = config('aggregator.settings')->get('source.list_max');
     if ($aggregator_summary_items) {
-      $summary_items = array();
-      $items = db_query_range('SELECT i.title, i.timestamp, i.link, f.title as feed_title, f.link as feed_link FROM {aggregator_category_item} ci LEFT JOIN {aggregator_item} i ON i.iid = ci.iid LEFT JOIN {aggregator_feed} f ON i.fid = f.fid WHERE ci.cid = :cid ORDER BY i.timestamp DESC', 0, $aggregator_summary_items, array(':cid' => $category->cid));
-      foreach ($items as $item) {
-        $summary_items[] = theme('aggregator_summary_item', array('item' => $item));
+      if ($items = aggregator_load_feed_items('category', $category, $aggregator_summary_items)) {
+        $summary_items = entity_view_multiple($items, 'summary');
       }
     }
     $category->url = url('aggregator/categories/' . $category->cid);
@@ -527,7 +517,11 @@ function theme_aggregator_page_opml($variables) {
  */
 function template_preprocess_aggregator_summary_items(&$variables) {
   $variables['title'] = check_plain($variables['source']->title);
-  $variables['summary_list'] = theme('item_list', array('items' => $variables['summary_items']));
+  $rendered_items = array();
+  foreach (element_children($variables['summary_items']) as $key) {
+    $rendered_items[] = drupal_render($variables['summary_items'][$key]);
+  }
+  $variables['summary_list'] = theme('item_list', array('items' => $rendered_items));
   $variables['source_url'] = $variables['source']->url;
 }
 
@@ -537,19 +531,19 @@ function template_preprocess_aggregator_summary_items(&$variables) {
  * @see aggregator-summary-item.tpl.php
  */
 function template_preprocess_aggregator_summary_item(&$variables) {
-  $item = $variables['item'];
+  $item = $variables['aggregator_item'];
 
-  $variables['item_url'] = l(check_plain($item->title), check_url(url($item->link, array('absolute' => TRUE))), array(
+  $variables['item_url'] = l(check_plain($item->label()), check_url(url($item->link->value, array('absolute' => TRUE))), array(
     'attributes' => array(
       'class' => array('feed-item-url',),
     ),
   ));
   $variables['item_age'] = theme('datetime', array(
     'attributes' => array(
-      'datetime' => format_date($item->timestamp, 'html_datetime', '', 'UTC'),
+      'datetime' => format_date($item->timestamp->value, 'html_datetime', '', 'UTC'),
       'class' => array('feed-item-age',),
     ),
-    'text' => t('%age old', array('%age' => format_interval(REQUEST_TIME - $item->timestamp))),
+    'text' => t('%age old', array('%age' => format_interval(REQUEST_TIME - $item->timestamp->value))),
     'html' => TRUE,
   ));
 }
diff --git a/core/modules/aggregator/aggregator.processor.inc b/core/modules/aggregator/aggregator.processor.inc
index b333a96..05b9d2b 100644
--- a/core/modules/aggregator/aggregator.processor.inc
+++ b/core/modules/aggregator/aggregator.processor.inc
@@ -22,26 +22,46 @@ function aggregator_aggregator_process($feed) {
   if (is_object($feed)) {
     if (is_array($feed->items)) {
       foreach ($feed->items as $item) {
+        // @todo: The default entity render controller always returns an empty
+        //   array, which is ignored in aggregator_save_item() currently. Should
+        //   probably be fixed.
+        if (empty($item['title'])) {
+          continue;
+        }
+
         // Save this item. Try to avoid duplicate entries as much as possible. If
         // we find a duplicate entry, we resolve it and pass along its ID is such
         // that we can update it if needed.
         if (!empty($item['guid'])) {
-          $entry = db_query("SELECT iid, timestamp FROM {aggregator_item} WHERE fid = :fid AND guid = :guid", array(':fid' => $feed->fid, ':guid' => $item['guid']))->fetchObject();
+          $values = array('fid' => $feed->fid, 'guid' => $item['guid']);
         }
         elseif ($item['link'] && $item['link'] != $feed->link && $item['link'] != $feed->url) {
-          $entry = db_query("SELECT iid, timestamp FROM {aggregator_item} WHERE fid = :fid AND link = :link", array(':fid' => $feed->fid, ':link' => $item['link']))->fetchObject();
+          $values = array('fid' => $feed->fid, 'link' => $item['link']);
+        }
+        else {
+          $values = array('fid' => $feed->fid, 'title' => $item['title']);
+        }
+
+        // Try to load an existing entry.
+        if ($entry = entity_load_multiple_by_properties('aggregator_item', $values)) {
+          $entry = reset($entry);
         }
         else {
-          $entry = db_query("SELECT iid, timestamp FROM {aggregator_item} WHERE fid = :fid AND title = :title", array(':fid' => $feed->fid, ':title' => $item['title']))->fetchObject();
+          $entry = entity_create('aggregator_item', array());
         }
-        if (!$item['timestamp']) {
-          $item['timestamp'] = isset($entry->timestamp) ? $entry->timestamp : REQUEST_TIME;
+        if ($item['timestamp']) {
+          $entry->timestamp->value = $item['timestamp'];
         }
 
         // Make sure the item title and author fit in the 255 varchar column.
-        $item['title'] = truncate_utf8($item['title'], 255, TRUE, TRUE);
-        $item['author'] = truncate_utf8($item['author'], 255, TRUE, TRUE);
-        aggregator_save_item(array('iid' => (isset($entry->iid) ? $entry->iid : ''), 'fid' => $feed->fid, 'timestamp' => $item['timestamp'], 'title' => $item['title'], 'link' => $item['link'], 'author' => $item['author'], 'description' => $item['description'], 'guid' => $item['guid']));
+        $entry->title->value = truncate_utf8($item['title'], 255, TRUE, TRUE);
+        $entry->author->value = truncate_utf8($item['author'], 255, TRUE, TRUE);
+
+        $entry->fid->value = $feed->fid;
+        $entry->link->value = $item['link'];
+        $entry->description->value = $item['description'];
+        $entry->guid->value = $item['guid'];
+        $entry->save();
       }
     }
   }
@@ -52,14 +72,7 @@ function aggregator_aggregator_process($feed) {
  */
 function aggregator_aggregator_remove($feed) {
   $iids = db_query('SELECT iid FROM {aggregator_item} WHERE fid = :fid', array(':fid' => $feed->fid))->fetchCol();
-  if ($iids) {
-    db_delete('aggregator_category_item')
-      ->condition('iid', $iids, 'IN')
-      ->execute();
-  }
-  db_delete('aggregator_item')
-    ->condition('fid', $feed->fid)
-    ->execute();
+  entity_delete_multiple('aggregator_item', $iids);
 
   drupal_set_message(t('The news items from %site have been removed.', array('%site' => $feed->title)));
 }
@@ -139,48 +152,6 @@ function _aggregator_characters($length) {
 }
 
 /**
- * Adds/edits/deletes an aggregator item.
- *
- * @param $edit
- *   An associative array describing the item to be added/edited/deleted.
- */
-function aggregator_save_item($edit) {
-  if ($edit['title'] && empty($edit['iid'])) {
-    $edit['iid'] = db_insert('aggregator_item')
-      ->fields(array(
-        'title' => $edit['title'],
-        'link' => $edit['link'],
-        'author' => $edit['author'],
-        'description' => $edit['description'],
-        'guid' => $edit['guid'],
-        'timestamp' => $edit['timestamp'],
-        'fid' => $edit['fid'],
-      ))
-      ->execute();
-  }
-  if ($edit['iid'] && !$edit['title']) {
-    db_delete('aggregator_item')
-      ->condition('iid', $edit['iid'])
-      ->execute();
-    db_delete('aggregator_category_item')
-      ->condition('iid', $edit['iid'])
-      ->execute();
-  }
-  elseif ($edit['title'] && $edit['link']) {
-    // file the items in the categories indicated by the feed
-    $result = db_query('SELECT cid FROM {aggregator_category_feed} WHERE fid = :fid', array(':fid' => $edit['fid']));
-    foreach ($result as $category) {
-      db_merge('aggregator_category_item')
-        ->key(array(
-          'iid' => $edit['iid'],
-          'cid' => $category->cid,
-        ))
-        ->execute();
-    }
-  }
-}
-
-/**
  * Expires items from a feed depending on expiration settings.
  *
  * @param $feed
@@ -198,12 +169,7 @@ function aggregator_expire($feed) {
     ))
     ->fetchCol();
     if ($iids) {
-      db_delete('aggregator_category_item')
-        ->condition('iid', $iids, 'IN')
-        ->execute();
-      db_delete('aggregator_item')
-        ->condition('iid', $iids, 'IN')
-        ->execute();
+      entity_delete_multiple('aggregator_item', $iids);
     }
   }
 }
diff --git a/core/modules/aggregator/lib/Drupal/aggregator/Item.php b/core/modules/aggregator/lib/Drupal/aggregator/Item.php
new file mode 100644
index 0000000..b70ea1e
--- /dev/null
+++ b/core/modules/aggregator/lib/Drupal/aggregator/Item.php
@@ -0,0 +1,36 @@
+<?php
+
+/**
+ * @file
+ * Definition of Drupal\aggregator\Item.
+ */
+
+namespace Drupal\aggregator;
+
+use Drupal\Core\Entity\ContentEntityInterface;
+use Drupal\Core\Entity\EntityNG;
+
+/**
+ * Defines the aggregator item entity class.
+ */
+class Item extends EntityNG implements ContentEntityInterface {
+
+  public function __construct(array $values, $entity_type) {
+    parent::__construct($values, $entity_type);
+  }
+
+  /**
+   * Implements Drupal\Core\Entity\EntityInterface::id().
+   */
+  public function id() {
+    return $this->get('iid')->value;
+  }
+
+  /**
+   * Implements Drupal\Core\Entity\EntityInterface::label().
+   */
+  public function label($langcode = NULL) {
+    return $this->title->value;
+  }
+}
+
diff --git a/core/modules/aggregator/lib/Drupal/aggregator/ItemRenderController.php b/core/modules/aggregator/lib/Drupal/aggregator/ItemRenderController.php
new file mode 100644
index 0000000..298c285
--- /dev/null
+++ b/core/modules/aggregator/lib/Drupal/aggregator/ItemRenderController.php
@@ -0,0 +1,31 @@
+<?php
+
+/**
+ * @file
+ * Definition of Drupal\aggregator\ItemRenderController.
+ */
+
+namespace Drupal\aggregator;
+
+use Drupal\Core\Entity\EntityInterface;
+use Drupal\Core\Entity\EntityRenderController;
+
+/**
+ * Render controller for aggregators.
+ */
+class ItemRenderController extends EntityRenderController {
+
+  /**
+   * Overrides Drupal\Core\Entity\EntityRenderController::getBuildDefaults().
+   */
+  protected function getBuildDefaults(EntityInterface $entity, $view_mode, $langcode) {
+    $defaults = parent::getBuildDefaults($entity, $view_mode, $langcode);
+
+    // Use a different template for the summary view mode.
+    if ($view_mode == 'summary') {
+      $defaults['#theme'] = 'aggregator_summary_item';
+    }
+    return $defaults;
+  }
+
+}
diff --git a/core/modules/aggregator/lib/Drupal/aggregator/ItemStorageController.php b/core/modules/aggregator/lib/Drupal/aggregator/ItemStorageController.php
new file mode 100644
index 0000000..46d220f
--- /dev/null
+++ b/core/modules/aggregator/lib/Drupal/aggregator/ItemStorageController.php
@@ -0,0 +1,118 @@
+<?php
+
+/**
+ * @file
+ * Definition of Drupal\aggregator\ItemStorageController.
+ */
+
+namespace Drupal\aggregator;
+
+use Drupal\Core\Entity\DatabaseStorageControllerNG;
+use Drupal\Core\Entity\EntityInterface;
+
+/**
+ * Controller class for aggregators items.
+ *
+ * This extends the Drupal\Core\Entity\DatabaseStorageController class, adding
+ * required special handling for feed item entities.
+ */
+class ItemStorageController extends DatabaseStorageControllerNG {
+
+  /**
+   * Overrides Drupal\Core\Entity\DataBaseStorageController::__construct().
+   */
+  public function create(array $values) {
+    $entity = parent::create($values);
+
+    // Set an initial timestamp, this will be overwritten if known.
+    $entity->timestamp->value = REQUEST_TIME;
+    return $entity;
+  }
+
+  /**
+   * Overrides Drupal\Core\Entity\DataBaseStorageController::attachLoad().
+   */
+  protected function attachLoad(&$queried_entities, $load_revision = FALSE) {
+    parent::attachLoad($queried_entities, $load_revision);
+    foreach ($queried_entities as $item) {
+      $item->categories = db_query('SELECT c.title, c.cid FROM {aggregator_category_item} ci LEFT JOIN {aggregator_category} c ON ci.cid = c.cid WHERE ci.iid = :iid ORDER BY c.title', array(':iid' => $item->id()))->fetchAll();
+    }
+  }
+
+  /**
+   * Overrides Drupal\Core\Entity\DataBaseStorageController::preDelete().
+   */
+  protected function preDelete($entities) {
+    parent::preDelete($entities);
+
+    db_delete('aggregator_category_item')
+      ->condition('iid', array_keys($entities), 'IN')
+      ->execute();
+  }
+
+  /**
+   * Overrides Drupal\Core\Entity\DataBaseStorageController::postSave().
+   */
+  protected function postSave(EntityInterface $entity, $update) {
+    parent::postSave($entity, $update);
+
+    $result = db_query('SELECT cid FROM {aggregator_category_feed} WHERE fid = :fid', array(':fid' => $entity->fid->value));
+    foreach ($result as $category) {
+      db_merge('aggregator_category_item')
+        ->key(array(
+          'iid' => $entity->id(),
+          'cid' => $category->cid,
+        ))
+        ->execute();
+    }
+  }
+
+  /**
+   * Implements Drupal\Core\Entity\DataBaseStorageControllerNG::baseFieldDefinitions().
+   */
+  public function baseFieldDefinitions() {
+    $fields['iid'] = array(
+      'label' => t('ID'),
+      'description' => t('The ID of the aggregor item.'),
+      'type' => 'integer_field',
+      'read-only' => TRUE,
+    );
+    $fields['fid'] = array(
+      'label' => t('Aggregator feed ID'),
+      'description' => t('The ID of the aggregator feed.'),
+      'type' => 'integer_field',
+    );
+    $fields['title'] = array(
+      'label' => t('Title'),
+      'description' => t('The title of the feed item.'),
+      'type' => 'string_field',
+    );
+    $fields['link'] = array(
+      'label' => t('Link'),
+      'description' => t('The link of the feed item.'),
+      'type' => 'string_field',
+    );
+    $fields['author'] = array(
+      'label' => t('Author'),
+      'description' => t('The author of the feed item.'),
+      'type' => 'string_field',
+    );
+    $fields['description'] = array(
+      'label' => t('Description'),
+      'description' => t('The body of the feed item.'),
+      'type' => 'string_field',
+    );
+    $fields['timestamp'] = array(
+      'label' => t('Posted timestamp'),
+      'description' => t('Posted date of the feed item, as a Unix timestamp.'),
+      'type' => 'integer_field',
+    );
+    $fields['guid'] = array(
+      'label' => t('GUID'),
+      'description' => t('Unique identifier for the feed item.'),
+      'type' => 'string_field',
+    );
+    return $fields;
+  }
+
+}