diff --git a/core/lib/Drupal/Core/Config/DatabaseStorage.php b/core/lib/Drupal/Core/Config/DatabaseStorage.php
index 930eea1..175e2d4 100644
--- a/core/lib/Drupal/Core/Config/DatabaseStorage.php
+++ b/core/lib/Drupal/Core/Config/DatabaseStorage.php
@@ -181,7 +181,7 @@ protected function ensureTableExists()  {
   /**
    * Defines the schema for the configuration table.
    */
-  protected static function schemaDefinition() {
+  public static function schemaDefinition() {
     $schema = array(
       'description' => 'The base table for configuration data.',
       'fields' => array(
diff --git a/core/lib/Drupal/Core/Config/Entity/ConfigEntityBase.php b/core/lib/Drupal/Core/Config/Entity/ConfigEntityBase.php
index 08e7e19..72460a2 100644
--- a/core/lib/Drupal/Core/Config/Entity/ConfigEntityBase.php
+++ b/core/lib/Drupal/Core/Config/Entity/ConfigEntityBase.php
@@ -323,12 +323,14 @@ public function preSave(EntityStorageInterface $storage) {
 
     // Ensure this entity's UUID does not exist with a different ID, regardless
     // of whether it's new or updated.
-    $matching_entities = $storage->getQuery()
-      ->condition('uuid', $this->uuid())
-      ->execute();
-    $matched_entity = reset($matching_entities);
-    if (!empty($matched_entity) && ($matched_entity != $this->id()) && $matched_entity != $this->getOriginalId()) {
-      throw new ConfigDuplicateUUIDException("Attempt to save a configuration entity '{$this->id()}' with UUID '{$this->uuid()}' when this UUID is already used for '$matched_entity'");
+    if ($uuid = $this->uuid()) {
+      $matching_entities = $storage->getQuery()
+        ->condition('uuid', $uuid)
+        ->execute();
+      $matched_entity = reset($matching_entities);
+      if (!empty($matched_entity) && ($matched_entity != $this->id()) && $matched_entity != $this->getOriginalId()) {
+        throw new ConfigDuplicateUUIDException("Attempt to save a configuration entity '{$this->id()}' with UUID '$uuid' when this UUID is already used for '$matched_entity'");
+      }
     }
 
     // If this entity is not new, load the original entity for comparison.
diff --git a/core/lib/Drupal/Core/Field/FieldItemInterface.php b/core/lib/Drupal/Core/Field/FieldItemInterface.php
index a257dd0..14cf9e9 100644
--- a/core/lib/Drupal/Core/Field/FieldItemInterface.php
+++ b/core/lib/Drupal/Core/Field/FieldItemInterface.php
@@ -98,7 +98,7 @@ public function getEntity();
   /**
    * Gets the langcode of the field values held in the object.
    *
-   * @return string
+   * @return $langcode
    *   The langcode.
    */
   public function getLangcode();
diff --git a/core/lib/Drupal/Core/Field/FieldItemListInterface.php b/core/lib/Drupal/Core/Field/FieldItemListInterface.php
index 2266c9c..e8bba02 100644
--- a/core/lib/Drupal/Core/Field/FieldItemListInterface.php
+++ b/core/lib/Drupal/Core/Field/FieldItemListInterface.php
@@ -44,7 +44,7 @@ public function setLangcode($langcode);
   /**
    * Gets the langcode of the field values held in the object.
    *
-   * @return string
+   * @return $langcode
    *   The langcode.
    */
   public function getLangcode();
diff --git a/core/lib/Drupal/Core/KeyValueStore/DatabaseStorage.php b/core/lib/Drupal/Core/KeyValueStore/DatabaseStorage.php
index aca4f31..4954a52 100644
--- a/core/lib/Drupal/Core/KeyValueStore/DatabaseStorage.php
+++ b/core/lib/Drupal/Core/KeyValueStore/DatabaseStorage.php
@@ -5,6 +5,7 @@
 use Drupal\Component\Serialization\SerializationInterface;
 use Drupal\Core\Database\Query\Merge;
 use Drupal\Core\Database\Connection;
+use Drupal\Core\Database\SchemaObjectExistsException;
 use Drupal\Core\DependencyInjection\DependencySerializationTrait;
 
 /**
@@ -61,10 +62,16 @@ public function __construct($collection, SerializationInterface $serializer, Con
    * {@inheritdoc}
    */
   public function has($key) {
-    return (bool) $this->connection->query('SELECT 1 FROM {' . $this->connection->escapeTable($this->table) . '} WHERE collection = :collection AND name = :key', array(
-      ':collection' => $this->collection,
-      ':key' => $key,
-    ))->fetchField();
+    try {
+      return (bool) $this->connection->query('SELECT 1 FROM {' . $this->connection->escapeTable($this->table) . '} WHERE collection = :collection AND name = :key', array(
+        ':collection' => $this->collection,
+        ':key' => $key,
+      ))->fetchField();
+    }
+    catch (\Exception $e) {
+      $this->catchException($e);
+      return FALSE;
+    }
   }
 
   /**
@@ -84,6 +91,7 @@ public function getMultiple(array $keys) {
       // @todo: Perhaps if the database is never going to be available,
       // key/value requests should return FALSE in order to allow exception
       // handling to occur but for now, keep it an array, always.
+      $this->catchException($e);
     }
     return $values;
   }
@@ -92,7 +100,14 @@ public function getMultiple(array $keys) {
    * {@inheritdoc}
    */
   public function getAll() {
-    $result = $this->connection->query('SELECT name, value FROM {' . $this->connection->escapeTable($this->table) . '} WHERE collection = :collection', array(':collection' => $this->collection));
+    try {
+      $result = $this->connection->query('SELECT name, value FROM {' . $this->connection->escapeTable($this->table) . '} WHERE collection = :collection', array(':collection' => $this->collection));
+    }
+    catch (\Exception $e) {
+      $this->catchException($e);
+      $result = [];
+    }
+
     $values = array();
 
     foreach ($result as $item) {
@@ -107,40 +122,75 @@ public function getAll() {
    * {@inheritdoc}
    */
   public function set($key, $value) {
-    $this->connection->merge($this->table)
-      ->keys(array(
-        'name' => $key,
-        'collection' => $this->collection,
-      ))
-      ->fields(array('value' => $this->serializer->encode($value)))
-      ->execute();
+    $try_again = FALSE;
+    try {
+      $this->connection->merge($this->table)
+        ->keys(array(
+          'name' => $key,
+          'collection' => $this->collection,
+        ))
+        ->fields(array('value' => $this->serializer->encode($value)))
+        ->execute();
+    }
+    catch (\Exception $e) {
+      // If there was an exception, try to create the table.
+      if (!$try_again = $this->ensureTableExists()) {
+        // If the exception happened for other reason than the missing bin
+        // table, propagate the exception.
+        throw $e;
+      }
+    }
+    // Now that the bin has been created, try again if necessary.
+    if ($try_again) {
+      $this->set($key, $value);
+    }
   }
 
   /**
    * {@inheritdoc}
    */
   public function setIfNotExists($key, $value) {
-    $result = $this->connection->merge($this->table)
-      ->insertFields(array(
-        'collection' => $this->collection,
-        'name' => $key,
-        'value' => $this->serializer->encode($value),
-      ))
-      ->condition('collection', $this->collection)
-      ->condition('name', $key)
-      ->execute();
-    return $result == Merge::STATUS_INSERT;
+    $try_again = FALSE;
+    try {
+      $result = $this->connection->merge($this->table)
+        ->insertFields(array(
+          'collection' => $this->collection,
+          'name' => $key,
+          'value' => $this->serializer->encode($value),
+        ))
+        ->condition('collection', $this->collection)
+        ->condition('name', $key)
+        ->execute();
+      return $result == Merge::STATUS_INSERT;
+    }
+    catch (\Exception $e) {
+      // If there was an exception, try to create the table.
+      if (!$try_again = $this->ensureTableExists()) {
+        // If the exception happened for other reason than the missing bin
+        // table, propagate the exception.
+        throw $e;
+      }
+    }
+    // Now that the bin has been created, try again if necessary.
+    if ($try_again) {
+      return $this->setIfNotExists($key, $value);
+    }
   }
 
   /**
    * {@inheritdoc}
    */
   public function rename($key, $new_key) {
-    $this->connection->update($this->table)
-      ->fields(array('name' => $new_key))
-      ->condition('collection', $this->collection)
-      ->condition('name', $key)
-      ->execute();
+    try {
+      $this->connection->update($this->table)
+        ->fields(array('name' => $new_key))
+        ->condition('collection', $this->collection)
+        ->condition('name', $key)
+        ->execute();
+    }
+    catch (\Exception $e) {
+      $this->catchException($e);
+    }
   }
 
   /**
@@ -149,20 +199,101 @@ public function rename($key, $new_key) {
   public function deleteMultiple(array $keys) {
     // Delete in chunks when a large array is passed.
     while ($keys) {
+      try {
+        $this->connection->delete($this->table)
+          ->condition('name', array_splice($keys, 0, 1000), 'IN')
+          ->condition('collection', $this->collection)
+          ->execute();
+      }
+      catch (\Exception $e) {
+        $this->catchException($e);
+      }
+    }
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function deleteAll() {
+    try {
       $this->connection->delete($this->table)
-        ->condition('name', array_splice($keys, 0, 1000), 'IN')
         ->condition('collection', $this->collection)
         ->execute();
     }
+    catch (\Exception $e) {
+      $this->catchException($e);
+    }
   }
 
   /**
-   * {@inheritdoc}
+   * Check if the batch table exists and create it if not.
    */
-  public function deleteAll() {
-    $this->connection->delete($this->table)
-      ->condition('collection', $this->collection)
-      ->execute();
+  protected function ensureTableExists() {
+    try {
+      $database_schema = $this->connection->schema();
+      if (!$database_schema->tableExists($this->table)) {
+        $database_schema->createTable($this->table, $this->schemaDefinition());
+        return TRUE;
+      }
+    }
+    // If another process has already created the batch table, attempting to
+    // recreate it will throw an exception. In this case just catch the
+    // exception and do nothing.
+    catch (SchemaObjectExistsException $e) {
+      return TRUE;
+    }
+    return FALSE;
+  }
+
+
+  /**
+   * Act on an exception when batch might be stale.
+   *
+   * If the table does not yet exist, that's fine, but if the table exists and
+   * yet the query failed, then the batch is stale and the exception needs
+   * to propagate.
+   *
+   * @param \Exception $e
+   *   The exception.
+   *
+   * @throws \Exception
+   */
+  protected function catchException(\Exception $e) {
+    if ($this->connection->schema()->tableExists($this->table)) {
+      throw $e;
+    }
+  }
+
+  /**
+   * Defines the schema for the key_value table.
+   */
+  public static function schemaDefinition() {
+    return [
+      'description' => 'Generic key-value storage table. See the state system for an example.',
+      'fields' => [
+        'collection' => [
+          'description' => 'A named collection of key and value pairs.',
+          'type' => 'varchar_ascii',
+          'length' => 128,
+          'not null' => TRUE,
+          'default' => '',
+        ],
+        'name' => [
+          'description' => 'The key of the key-value pair. As KEY is a SQL reserved keyword, name was chosen instead.',
+          'type' => 'varchar_ascii',
+          'length' => 128,
+          'not null' => TRUE,
+          'default' => '',
+        ],
+        'value' => [
+          'description' => 'The value.',
+          'type' => 'blob',
+          'not null' => TRUE,
+          'size' => 'big',
+        ],
+      ],
+      'primary key' => ['collection', 'name'],
+    ];
   }
 
 }
diff --git a/core/lib/Drupal/Core/KeyValueStore/DatabaseStorageExpirable.php b/core/lib/Drupal/Core/KeyValueStore/DatabaseStorageExpirable.php
index 9f3b428..64397f2 100644
--- a/core/lib/Drupal/Core/KeyValueStore/DatabaseStorageExpirable.php
+++ b/core/lib/Drupal/Core/KeyValueStore/DatabaseStorageExpirable.php
@@ -34,71 +34,122 @@ public function __construct($collection, SerializationInterface $serializer, Con
    * {@inheritdoc}
    */
   public function has($key) {
-    return (bool) $this->connection->query('SELECT 1 FROM {' . $this->connection->escapeTable($this->table) . '} WHERE collection = :collection AND name = :key AND expire > :now', array(
-      ':collection' => $this->collection,
-      ':key' => $key,
-      ':now' => REQUEST_TIME,
-    ))->fetchField();
+    try {
+      return (bool) $this->connection->query('SELECT 1 FROM {' . $this->connection->escapeTable($this->table) . '} WHERE collection = :collection AND name = :key AND expire > :now', array(
+        ':collection' => $this->collection,
+        ':key' => $key,
+        ':now' => REQUEST_TIME,
+      ))->fetchField();
+    }
+    catch (\Exception $e) {
+      $this->catchException($e);
+      return FALSE;
+    }
   }
 
   /**
    * {@inheritdoc}
    */
   public function getMultiple(array $keys) {
-    $values = $this->connection->query(
-      'SELECT name, value FROM {' . $this->connection->escapeTable($this->table) . '} WHERE expire > :now AND name IN ( :keys[] ) AND collection = :collection',
-      array(
-        ':now' => REQUEST_TIME,
-        ':keys[]' => $keys,
-        ':collection' => $this->collection,
-      ))->fetchAllKeyed();
-    return array_map(array($this->serializer, 'decode'), $values);
+    try {
+      $values = $this->connection->query(
+        'SELECT name, value FROM {' . $this->connection->escapeTable($this->table) . '} WHERE expire > :now AND name IN ( :keys[] ) AND collection = :collection',
+        array(
+          ':now' => REQUEST_TIME,
+          ':keys[]' => $keys,
+          ':collection' => $this->collection,
+        ))->fetchAllKeyed();
+      return array_map(array($this->serializer, 'decode'), $values);
+    }
+    catch (\Exception $e) {
+      // @todo: Perhaps if the database is never going to be available,
+      // key/value requests should return FALSE in order to allow exception
+      // handling to occur but for now, keep it an array, always.
+      $this->catchException($e);
+    }
+    return [];
   }
 
   /**
    * {@inheritdoc}
    */
   public function getAll() {
-    $values = $this->connection->query(
-      'SELECT name, value FROM {' . $this->connection->escapeTable($this->table) . '} WHERE collection = :collection AND expire > :now',
-      array(
-        ':collection' => $this->collection,
-        ':now' => REQUEST_TIME
-      ))->fetchAllKeyed();
-    return array_map(array($this->serializer, 'decode'), $values);
+    try {
+      $values = $this->connection->query(
+        'SELECT name, value FROM {' . $this->connection->escapeTable($this->table) . '} WHERE collection = :collection AND expire > :now',
+        array(
+          ':collection' => $this->collection,
+          ':now' => REQUEST_TIME
+        ))->fetchAllKeyed();
+      return array_map(array($this->serializer, 'decode'), $values);
+    }
+    catch (\Exception $e) {
+      $this->catchException($e);
+    }
+    return [];
   }
 
   /**
    * {@inheritdoc}
    */
   function setWithExpire($key, $value, $expire) {
-    $this->connection->merge($this->table)
-      ->keys(array(
-        'name' => $key,
-        'collection' => $this->collection,
-      ))
-      ->fields(array(
-        'value' => $this->serializer->encode($value),
-        'expire' => REQUEST_TIME + $expire,
-      ))
-      ->execute();
+    $try_again = FALSE;
+    try {
+      $this->connection->merge($this->table)
+        ->keys(array(
+          'name' => $key,
+          'collection' => $this->collection,
+        ))
+        ->fields(array(
+          'value' => $this->serializer->encode($value),
+          'expire' => REQUEST_TIME + $expire,
+        ))
+        ->execute();
+    }
+    catch (\Exception $e) {
+      // If there was an exception, try to create the table.
+      if (!$try_again = $this->ensureTableExists()) {
+        // If the exception happened for other reason than the missing bin
+        // table, propagate the exception.
+        throw $e;
+      }
+    }
+    // Now that the bin has been created, try again if necessary.
+    if ($try_again) {
+      $this->setWithExpire($key, $value, $expire);
+    }
   }
 
   /**
    * {@inheritdoc}
    */
   function setWithExpireIfNotExists($key, $value, $expire) {
-    $result = $this->connection->merge($this->table)
-      ->insertFields(array(
-        'collection' => $this->collection,
-        'name' => $key,
-        'value' => $this->serializer->encode($value),
-        'expire' => REQUEST_TIME + $expire,
-      ))
-      ->condition('collection', $this->collection)
-      ->condition('name', $key)
-      ->execute();
-    return $result == Merge::STATUS_INSERT;
+    $try_again = FALSE;
+    try {
+      $result = $this->connection->merge($this->table)
+        ->insertFields(array(
+          'collection' => $this->collection,
+          'name' => $key,
+          'value' => $this->serializer->encode($value),
+          'expire' => REQUEST_TIME + $expire,
+        ))
+        ->condition('collection', $this->collection)
+        ->condition('name', $key)
+        ->execute();
+      return $result == Merge::STATUS_INSERT;
+    }
+    catch (\Exception $e) {
+      // If there was an exception, try to create the table.
+      if (!$try_again = $this->ensureTableExists()) {
+        // If the exception happened for other reason than the missing bin
+        // table, propagate the exception.
+        throw $e;
+      }
+    }
+    // Now that the bin has been created, try again if necessary.
+    if ($try_again) {
+      return $this->setWithExpireIfNotExists($key, $value, $expire);
+    }
   }
 
   /**
@@ -117,4 +168,47 @@ public function deleteMultiple(array $keys) {
     parent::deleteMultiple($keys);
   }
 
+  /**
+   * Defines the schema for the key_value_expire table.
+   */
+  public static function schemaDefinition() {
+    return [
+      'description' => 'Generic key/value storage table with an expiration.',
+      'fields' => [
+        'collection' => [
+          'description' => 'A named collection of key and value pairs.',
+          'type' => 'varchar_ascii',
+          'length' => 128,
+          'not null' => TRUE,
+          'default' => '',
+        ],
+        'name' => [
+          // KEY is an SQL reserved word, so use 'name' as the key's field name.
+          'description' => 'The key of the key/value pair.',
+          'type' => 'varchar_ascii',
+          'length' => 128,
+          'not null' => TRUE,
+          'default' => '',
+        ],
+        'value' => [
+          'description' => 'The value of the key/value pair.',
+          'type' => 'blob',
+          'not null' => TRUE,
+          'size' => 'big',
+        ],
+        'expire' => [
+          'description' => 'The time since Unix epoch in seconds when this item expires. Defaults to the maximum possible time.',
+          'type' => 'int',
+          'not null' => TRUE,
+          'default' => 2147483647,
+        ],
+      ],
+      'primary key' => ['collection', 'name'],
+      'indexes' => [
+        'all' => ['name', 'collection', 'expire'],
+        'expire' => ['expire'],
+      ],
+    ];
+  }
+
 }
diff --git a/core/modules/field/tests/src/Kernel/FieldKernelTestBase.php b/core/modules/field/tests/src/Kernel/FieldKernelTestBase.php
index c864de8..b3660f2 100644
--- a/core/modules/field/tests/src/Kernel/FieldKernelTestBase.php
+++ b/core/modules/field/tests/src/Kernel/FieldKernelTestBase.php
@@ -47,7 +47,7 @@ protected function setUp() {
 
     $this->installEntitySchema('entity_test');
     $this->installEntitySchema('user');
-    $this->installSchema('system', ['sequences', 'key_value']);
+    $this->installSchema('system', ['sequences']);
 
     // Set default storage backend and configure the theme system.
     $this->installConfig(array('field', 'system'));
diff --git a/core/modules/file/src/Entity/File.php b/core/modules/file/src/Entity/File.php
index 6fd0cc7..0c34871 100644
--- a/core/modules/file/src/Entity/File.php
+++ b/core/modules/file/src/Entity/File.php
@@ -186,11 +186,7 @@ public static function preCreate(EntityStorageInterface $storage, array &$values
   public function preSave(EntityStorageInterface $storage) {
     parent::preSave($storage);
 
-    // The file itself might not exist or be available right now.
-    $uri = $this->getFileUri();
-    if ($size = @filesize($uri)) {
-      $this->setSize($size);
-    }
+    $this->setSize(filesize($this->getFileUri()));
   }
 
   /**
diff --git a/core/modules/file/src/Tests/FileManagedFileElementTest.php b/core/modules/file/src/Tests/FileManagedFileElementTest.php
index 07102a0..f5d5be3 100644
--- a/core/modules/file/src/Tests/FileManagedFileElementTest.php
+++ b/core/modules/file/src/Tests/FileManagedFileElementTest.php
@@ -171,27 +171,4 @@ public function testManagedFileRemoved() {
     $this->assertRaw('The file referenced by the Managed <em>file &amp; butter</em> field does not exist.');
   }
 
-  /**
-   * Ensure a file entity can be saved when the file does not exist on disk.
-   */
-  public function testFileRemovedFromDisk() {
-    $this->drupalGet('file/test/1/0/1');
-    $test_file = $this->getTestFile('text');
-    $file_field_name = 'files[nested_file][]';
-
-    $edit = [$file_field_name => drupal_realpath($test_file->getFileUri())];
-    $this->drupalPostForm(NULL, $edit, t('Upload'));
-    $this->drupalPostForm(NULL, array(), t('Save'));
-
-    $fid = $this->getLastFileId();
-    /** @var $file \Drupal\file\FileInterface */
-    $file = $this->container->get('entity_type.manager')->getStorage('file')->load($fid);
-    $file->setPermanent();
-    $file->save();
-    $this->assertTrue(file_unmanaged_delete($file->getFileUri()));
-    $file->save();
-    $this->assertTrue($file->isPermanent());
-    $file->delete();
-  }
-
 }
diff --git a/core/modules/language/src/ContentLanguageSettingsInterface.php b/core/modules/language/src/ContentLanguageSettingsInterface.php
index 7e1211d..3bb3d5d 100644
--- a/core/modules/language/src/ContentLanguageSettingsInterface.php
+++ b/core/modules/language/src/ContentLanguageSettingsInterface.php
@@ -39,7 +39,7 @@ public function setTargetBundle($target_bundle);
    * @param string $default_langcode
    *   The default language code.
    *
-   * @return $this
+   * @return $this;
    */
   public function setDefaultLangcode($default_langcode);
 
diff --git a/core/modules/simpletest/src/WebTestBase.php b/core/modules/simpletest/src/WebTestBase.php
index ebf52e4..35d2324 100644
--- a/core/modules/simpletest/src/WebTestBase.php
+++ b/core/modules/simpletest/src/WebTestBase.php
@@ -2631,7 +2631,7 @@ protected function assertNoResponse($code, $message = '', $group = 'Browser') {
    * @param $override_server_vars
    *   An array of server variables to override.
    *
-   * @return \Symfony\Component\HttpFoundation\Request
+   * @return $request
    *   The mocked request object.
    */
   protected function prepareRequestForGenerator($clean_urls = TRUE, $override_server_vars = array()) {
diff --git a/core/modules/system/src/Tests/KeyValueStore/DatabaseStorageTest.php b/core/modules/system/src/Tests/KeyValueStore/DatabaseStorageTest.php
index b433ac1..c8d7fe4 100644
--- a/core/modules/system/src/Tests/KeyValueStore/DatabaseStorageTest.php
+++ b/core/modules/system/src/Tests/KeyValueStore/DatabaseStorageTest.php
@@ -19,11 +19,6 @@ class DatabaseStorageTest extends StorageTestBase {
    */
   public static $modules = array('system');
 
-  protected function setUp() {
-    parent::setUp();
-    $this->installSchema('system', array('key_value'));
-  }
-
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/system/src/Tests/Path/UrlAliasFixtures.php b/core/modules/system/src/Tests/Path/UrlAliasFixtures.php
index a527fc5..1f71690 100644
--- a/core/modules/system/src/Tests/Path/UrlAliasFixtures.php
+++ b/core/modules/system/src/Tests/Path/UrlAliasFixtures.php
@@ -2,6 +2,7 @@
 
 namespace Drupal\system\Tests\Path;
 
+use Drupal\Core\KeyValueStore\DatabaseStorage;
 use Drupal\Core\Database\Connection;
 use Drupal\Core\Path\AliasStorage;
 
@@ -89,7 +90,7 @@ public function tableDefinition() {
     $schema = system_schema();
 
     $tables['url_alias'] = AliasStorage::schemaDefinition();
-    $tables['key_value'] = $schema['key_value'];
+    $tables['key_value'] = DatabaseStorage::schemaDefinition();
 
     return $tables;
   }
diff --git a/core/modules/system/src/Tests/Update/DbDumpTest.php b/core/modules/system/src/Tests/Update/DbDumpTest.php
index 3a6a927..0f7685a 100644
--- a/core/modules/system/src/Tests/Update/DbDumpTest.php
+++ b/core/modules/system/src/Tests/Update/DbDumpTest.php
@@ -83,10 +83,7 @@ protected function setUp() {
     $this->skipTests = Database::getConnection()->databaseType() !== 'mysql';
 
     // Create some schemas so our export contains tables.
-    $this->installSchema('system', [
-      'key_value_expire',
-      'sessions',
-    ]);
+    $this->installSchema('system', ['sessions']);
     $this->installSchema('dblog', ['watchdog']);
     $this->installEntitySchema('block_content');
     $this->installEntitySchema('user');
@@ -126,7 +123,6 @@ protected function setUp() {
       'cache_discovery',
       'cache_entity',
       'file_managed',
-      'key_value_expire',
       'menu_link_content',
       'menu_link_content_data',
       'sequences',
diff --git a/core/modules/system/system.install b/core/modules/system/system.install
index cdaeba6..29ab966 100644
--- a/core/modules/system/system.install
+++ b/core/modules/system/system.install
@@ -855,71 +855,6 @@ function system_install() {
  * Implements hook_schema().
  */
 function system_schema() {
-  $schema['key_value'] = array(
-    'description' => 'Generic key-value storage table. See the state system for an example.',
-    'fields' => array(
-      'collection' => array(
-        'description' => 'A named collection of key and value pairs.',
-        'type' => 'varchar_ascii',
-        'length' => 128,
-        'not null' => TRUE,
-        'default' => '',
-      ),
-      'name' => array(
-        'description' => 'The key of the key-value pair. As KEY is a SQL reserved keyword, name was chosen instead.',
-        'type' => 'varchar_ascii',
-        'length' => 128,
-        'not null' => TRUE,
-        'default' => '',
-      ),
-      'value' => array(
-        'description' => 'The value.',
-        'type' => 'blob',
-        'not null' => TRUE,
-        'size' => 'big',
-      ),
-    ),
-    'primary key' => array('collection', 'name'),
-  );
-
-  $schema['key_value_expire'] = array(
-    'description' => 'Generic key/value storage table with an expiration.',
-    'fields' => array(
-      'collection' => array(
-        'description' => 'A named collection of key and value pairs.',
-        'type' => 'varchar_ascii',
-        'length' => 128,
-        'not null' => TRUE,
-        'default' => '',
-      ),
-      'name' => array(
-        // KEY is an SQL reserved word, so use 'name' as the key's field name.
-        'description' => 'The key of the key/value pair.',
-        'type' => 'varchar_ascii',
-        'length' => 128,
-        'not null' => TRUE,
-        'default' => '',
-      ),
-      'value' => array(
-        'description' => 'The value of the key/value pair.',
-        'type' => 'blob',
-        'not null' => TRUE,
-        'size' => 'big',
-      ),
-      'expire' => array(
-        'description' => 'The time since Unix epoch in seconds when this item expires. Defaults to the maximum possible time.',
-        'type' => 'int',
-        'not null' => TRUE,
-        'default' => 2147483647,
-      ),
-    ),
-    'primary key' => array('collection', 'name'),
-    'indexes' => array(
-      'all' => array('name', 'collection', 'expire'),
-      'expire' => array('expire'),
-    ),
-  );
-
   $schema['sequences'] = array(
     'description' => 'Stores IDs.',
     'fields' => array(
diff --git a/core/modules/views/src/Plugin/views/query/QueryPluginBase.php b/core/modules/views/src/Plugin/views/query/QueryPluginBase.php
index e896660..5dfa0a0 100644
--- a/core/modules/views/src/Plugin/views/query/QueryPluginBase.php
+++ b/core/modules/views/src/Plugin/views/query/QueryPluginBase.php
@@ -160,7 +160,7 @@ public function getLimit() {
    * @param $where
    *   'where' or 'having'.
    *
-   * @return
+   * @return $group
    *   The group ID generated.
    */
   public function setWhereGroup($type = 'AND', $group = NULL, $where = 'where') {
diff --git a/core/modules/views/src/Plugin/views/query/Sql.php b/core/modules/views/src/Plugin/views/query/Sql.php
index 321ebf5..43b4a44 100644
--- a/core/modules/views/src/Plugin/views/query/Sql.php
+++ b/core/modules/views/src/Plugin/views/query/Sql.php
@@ -337,7 +337,7 @@ public function addRelationship($alias, JoinPluginBase $join, $base, $link_point
    * @param $alias
    *   A specific alias to use, rather than the default alias.
    *
-   * @return string
+   * @return $alias
    *   The alias of the table; this alias can be used to access information
    *   about the table and should always be used to refer to the table when
    *   adding parts to the query. Or FALSE if the table was not able to be
@@ -376,7 +376,7 @@ public function addTable($table, $relationship = NULL, JoinPluginBase $join = NU
    * @param $alias
    *   A specific alias to use, rather than the default alias.
    *
-   * @return string
+   * @return $alias
    *   The alias of the table; this alias can be used to access information
    *   about the table and should always be used to refer to the table when
    *   adding parts to the query. Or FALSE if the table was not able to be
@@ -723,7 +723,7 @@ public function getTableInfo($table) {
    *   - aggregate: Set to TRUE to indicate that this value should be
    *     aggregated in a GROUP BY.
    *
-   * @return string
+   * @return $name
    *   The name that this field can be referred to as. Usually this is the alias.
    */
   public function addField($table, $field, $alias = '', $params = array()) {
diff --git a/core/phpcs.xml.dist b/core/phpcs.xml.dist
index 15416ee..aa93c42 100644
--- a/core/phpcs.xml.dist
+++ b/core/phpcs.xml.dist
@@ -45,6 +45,7 @@
   <rule ref="Drupal.Commenting.FileComment"/>
   <rule ref="Drupal.Commenting.FunctionComment">
     <exclude name="Drupal.Commenting.FunctionComment.IncorrectTypeHint"/>
+    <exclude name="Drupal.Commenting.FunctionComment.$InReturnType"/>
     <exclude name="Drupal.Commenting.FunctionComment.InvalidNoReturn"/>
     <exclude name="Drupal.Commenting.FunctionComment.InvalidReturn"/>
     <exclude name="Drupal.Commenting.FunctionComment.InvalidReturnNotVoid"/>
diff --git a/core/tests/Drupal/KernelTests/Core/Entity/EntityAutocompleteTest.php b/core/tests/Drupal/KernelTests/Core/Entity/EntityAutocompleteTest.php
index f03599d..f9c3051 100644
--- a/core/tests/Drupal/KernelTests/Core/Entity/EntityAutocompleteTest.php
+++ b/core/tests/Drupal/KernelTests/Core/Entity/EntityAutocompleteTest.php
@@ -33,14 +33,6 @@ class EntityAutocompleteTest extends EntityKernelTestBase {
   protected $bundle = 'entity_test';
 
   /**
-   * {@inheritdoc}
-   */
-  protected function setUp() {
-    parent::setUp();
-    $this->installSchema('system', ['key_value']);
-  }
-
-  /**
    * Tests autocompletion edge cases with slashes in the names.
    */
   function testEntityReferenceAutocompletion() {
diff --git a/core/tests/Drupal/KernelTests/Core/Entity/FieldWidgetConstraintValidatorTest.php b/core/tests/Drupal/KernelTests/Core/Entity/FieldWidgetConstraintValidatorTest.php
index 50d173b..81c33d6 100644
--- a/core/tests/Drupal/KernelTests/Core/Entity/FieldWidgetConstraintValidatorTest.php
+++ b/core/tests/Drupal/KernelTests/Core/Entity/FieldWidgetConstraintValidatorTest.php
@@ -23,7 +23,6 @@ class FieldWidgetConstraintValidatorTest extends KernelTestBase {
   protected function setUp() {
     parent::setUp();
 
-    $this->installSchema('system', ['key_value']);
     $this->container->get('router.builder')->rebuild();
 
     $this->installEntitySchema('user');
diff --git a/core/tests/Drupal/Tests/Core/Config/Entity/ConfigEntityStorageTest.php b/core/tests/Drupal/Tests/Core/Config/Entity/ConfigEntityStorageTest.php
index 2c4a01b..f86e667 100644
--- a/core/tests/Drupal/Tests/Core/Config/Entity/ConfigEntityStorageTest.php
+++ b/core/tests/Drupal/Tests/Core/Config/Entity/ConfigEntityStorageTest.php
@@ -525,6 +525,7 @@ public function testSaveMismatch() {
     $config_object = $this->getMockBuilder('Drupal\Core\Config\Config')
       ->disableOriginalConstructor()
       ->getMock();
+
     $config_object->expects($this->atLeastOnce())
       ->method('isNew')
       ->will($this->returnValue(TRUE));
@@ -539,14 +540,16 @@ public function testSaveMismatch() {
       ->with('the_config_prefix.foo')
       ->will($this->returnValue($config_object));
 
+    $uuid = '7C1821EF-A96F-4BF0-B654-F683532EECB3';
     $this->entityQuery->expects($this->once())
       ->method('condition')
+      ->with('uuid', $uuid)
       ->will($this->returnSelf());
     $this->entityQuery->expects($this->once())
       ->method('execute')
       ->will($this->returnValue(array('baz')));
 
-    $entity = $this->getMockEntity(array('id' => 'foo'));
+    $entity = $this->getMockEntity(array('id' => 'foo', 'uuid' => $uuid));
     $this->entityStorage->save($entity);
   }
 
@@ -591,7 +594,8 @@ public function testSaveNoMismatch() {
       ->method('execute')
       ->will($this->returnValue(array('baz')));
 
-    $entity = $this->getMockEntity(array('id' => 'foo'));
+    $uuid = '7C1821EF-A96F-4BF0-B654-F683532EECB3';
+    $entity = $this->getMockEntity(array('id' => 'foo', 'uuid' => $uuid));
     $entity->setOriginalId('baz');
     $entity->enforceIsNew();
     $this->entityStorage->save($entity);