diff -u b/core/lib/Drupal/Core/Entity/Schema/ContentEntitySchemaHandler.php b/core/lib/Drupal/Core/Entity/Schema/ContentEntitySchemaHandler.php
--- b/core/lib/Drupal/Core/Entity/Schema/ContentEntitySchemaHandler.php
+++ b/core/lib/Drupal/Core/Entity/Schema/ContentEntitySchemaHandler.php
@@ -7,6 +7,7 @@
 
 namespace Drupal\Core\Entity\Schema;
 
+use Drupal\Core\Database\Connection;
 use Drupal\Core\Entity\ContentEntityDatabaseStorage;
 use Drupal\Core\Entity\ContentEntityTypeInterface;
 use Drupal\Core\Entity\EntityManagerInterface;
@@ -45,6 +46,20 @@
   protected $schema;
 
   /**
+   * The database connection to be used.
+   *
+   * @var \Drupal\Core\Database\Connection
+   */
+  protected $database;
+
+  /**
+   * A callable to invoke at the end of getEntitySchema().
+   *
+   * @var callable|NULL
+   */
+  protected $entitySchemaCustomizer;
+
+  /**
    * Constructs a ContentEntitySchemaHandler.
    *
    * @param \Drupal\Core\Entity\EntityManagerInterface $entity_manager
@@ -53,11 +68,17 @@
    *   The entity type.
    * @param \Drupal\Core\Entity\ContentEntityDatabaseStorage $storage
    *   The storage of the entity type. This must be an SQL-based storage.
+   * @param \Drupal\Core\Database\Connection $database
+   *   The database connection to be used.
+   * @param callable|NULL $entity_schema_customizer
+   *   (optional) A callable to invoke at the end of getEntitySchema().
    */
-  public function __construct(EntityManagerInterface $entity_manager, ContentEntityTypeInterface $entity_type, ContentEntityDatabaseStorage $storage) {
+  public function __construct(EntityManagerInterface $entity_manager, ContentEntityTypeInterface $entity_type, ContentEntityDatabaseStorage $storage, Connection $database, callable $entity_schema_customizer = NULL) {
     $this->entityType = $entity_type;
     $this->fieldStorageDefinitions = $entity_manager->getFieldStorageDefinitions($entity_type->id());
     $this->storage = $storage;
+    $this->database = $database;
+    $this->entitySchemaCustomizer = $entity_schema_customizer;
   }
 
   /**
@@ -125,6 +146,10 @@
         $this->processRevisionDataTable($schema[$tables['revision_data_table']]);
       }
 
+      // Perform additional customizations.
+      if (isset($this->entitySchemaCustomizer)) {
+        $schema = call_user_func($this->entitySchemaCustomizer, $schema);
+      }
       $this->schema[$entity_type_id] = $schema;
     }
 
reverted:
--- b/core/modules/aggregator/src/FeedSchemaHandler.php
+++ /dev/null
@@ -1,41 +0,0 @@
-<?php
-
-/**
- * @file
- * Contains \Drupal\aggregator\FeedSchemaHandler.
- */
-
-namespace Drupal\aggregator;
-
-use Drupal\Core\Entity\ContentEntityTypeInterface;
-use Drupal\Core\Entity\Schema\ContentEntitySchemaHandler;
-
-/**
- * Defines the feed schema handler.
- */
-class FeedSchemaHandler extends ContentEntitySchemaHandler {
-
-  /**
-   * {@inheritdoc}
-   */
-  protected function getEntitySchema(ContentEntityTypeInterface $entity_type, $reset = FALSE) {
-    $schema = parent::getEntitySchema($entity_type, $reset);
-
-    // Marking the respective fields as NOT NULL makes the indexes more
-    // performant.
-    $schema['aggregator_feed']['fields']['url']['not null'] = TRUE;
-    $schema['aggregator_feed']['fields']['queued']['not null'] = TRUE;
-    $schema['aggregator_feed']['fields']['title']['not null'] = TRUE;
-
-    $schema['aggregator_feed']['indexes'] += array(
-      'aggregator_feed__url'  => array(array('url', 255)),
-      'aggregator_feed__queued' => array('queued'),
-    );
-    $schema['aggregator_feed']['unique keys'] += array(
-      'aggregator_feed__title' => array('title'),
-    );
-
-    return $schema;
-  }
-
-}
diff -u b/core/modules/aggregator/src/FeedStorage.php b/core/modules/aggregator/src/FeedStorage.php
--- b/core/modules/aggregator/src/FeedStorage.php
+++ b/core/modules/aggregator/src/FeedStorage.php
@@ -7,8 +7,8 @@
 
 namespace Drupal\aggregator;
 
-use Drupal\aggregator\FeedInterface;
 use Drupal\Core\Entity\ContentEntityDatabaseStorage;
+use Drupal\Core\Entity\Schema\ContentEntitySchemaHandler;
 
 /**
  * Controller class for aggregator's feeds.
@@ -23,7 +23,22 @@
    */
   protected function schemaHandler() {
     if (!isset($this->schemaHandler)) {
-      $this->schemaHandler = new FeedSchemaHandler($this->entityManager, $this->entityType, $this, $this->database);
+      $this->schemaHandler = new ContentEntitySchemaHandler($this->entityManager, $this->entityType, $this, $this->database, function ($schema) {
+        // Marking the respective fields as NOT NULL makes the indexes more
+        // performant.
+        $schema['aggregator_feed']['fields']['url']['not null'] = TRUE;
+        $schema['aggregator_feed']['fields']['queued']['not null'] = TRUE;
+        $schema['aggregator_feed']['fields']['title']['not null'] = TRUE;
+
+        $schema['aggregator_feed']['indexes'] += array(
+          'aggregator_feed__url'  => array(array('url', 255)),
+          'aggregator_feed__queued' => array('queued'),
+        );
+        $schema['aggregator_feed']['unique keys'] += array(
+          'aggregator_feed__title' => array('title'),
+        );
+        return $schema;
+      });
     }
     return $this->schemaHandler;
   }
reverted:
--- b/core/modules/aggregator/src/ItemSchemaHandler.php
+++ /dev/null
@@ -1,41 +0,0 @@
-<?php
-
-/**
- * @file
- * Contains \Drupal\aggregator\ItemSchemaHandler.
- */
-
-namespace Drupal\aggregator;
-
-use Drupal\Core\Entity\ContentEntityTypeInterface;
-use Drupal\Core\Entity\Schema\ContentEntitySchemaHandler;
-
-/**
- * Defines the item schema handler.
- */
-class ItemSchemaHandler extends ContentEntitySchemaHandler {
-
-  /**
-   * {@inheritdoc}
-   */
-  protected function getEntitySchema(ContentEntityTypeInterface $entity_type, $reset = FALSE) {
-    $schema = parent::getEntitySchema($entity_type, $reset);
-
-    // Marking the respective fields as NOT NULL makes the indexes more
-    // performant.
-    $schema['aggregator_item']['fields']['timestamp']['not null'] = TRUE;
-
-    $schema['aggregator_item']['indexes'] += array(
-      'aggregator_item__timestamp' => array('timestamp'),
-    );
-    $schema['aggregator_item']['foreign keys'] += array(
-      'aggregator_item__aggregator_feed' => array(
-        'table' => 'aggregator_feed',
-        'columns' => array('fid' => 'fid'),
-      ),
-    );
-
-    return $schema;
-  }
-
-}
diff -u b/core/modules/aggregator/src/ItemStorage.php b/core/modules/aggregator/src/ItemStorage.php
--- b/core/modules/aggregator/src/ItemStorage.php
+++ b/core/modules/aggregator/src/ItemStorage.php
@@ -9,6 +9,7 @@
 
 use Drupal\Core\Entity\ContentEntityDatabaseStorage;
 use Drupal\Core\Entity\Query\QueryInterface;
+use Drupal\Core\Entity\Schema\ContentEntitySchemaHandler;
 
 /**
  * Controller class for aggregators items.
@@ -23,7 +24,22 @@
    */
   protected function schemaHandler() {
     if (!isset($this->schemaHandler)) {
-      $this->schemaHandler = new ItemSchemaHandler($this->entityManager, $this->entityType, $this, $this->database);
+      $this->schemaHandler = new ContentEntitySchemaHandler($this->entityManager, $this->entityType, $this, $this->database, function ($schema) {
+        // Marking the respective fields as NOT NULL makes the indexes more
+        // performant.
+        $schema['aggregator_item']['fields']['timestamp']['not null'] = TRUE;
+
+        $schema['aggregator_item']['indexes'] += array(
+          'aggregator_item__timestamp' => array('timestamp'),
+        );
+        $schema['aggregator_item']['foreign keys'] += array(
+          'aggregator_item__aggregator_feed' => array(
+            'table' => 'aggregator_feed',
+            'columns' => array('fid' => 'fid'),
+          ),
+        );
+        return $schema;
+      });
     }
     return $this->schemaHandler;
   }
reverted:
--- b/core/modules/block_content/src/BlockContentSchemaHandler.php
+++ /dev/null
@@ -1,35 +0,0 @@
-<?php
-
-/**
- * @file
- * Contains \Drupal\block_content\BlockContentSchemaHandler.
- */
-
-namespace Drupal\block_content;
-
-use Drupal\Core\Entity\ContentEntityTypeInterface;
-use Drupal\Core\Entity\Schema\ContentEntitySchemaHandler;
-
-/**
- * Defines the block content schema handler.
- */
-class BlockContentSchemaHandler extends ContentEntitySchemaHandler {
-
-  /**
-   * {@inheritdoc}
-   */
-  protected function getEntitySchema(ContentEntityTypeInterface $entity_type, $reset = FALSE) {
-    $schema = parent::getEntitySchema($entity_type, $reset);
-
-    // Marking the respective fields as NOT NULL makes the indexes more
-    // performant.
-    $schema['block_content_field_data']['fields']['info']['not null'] = TRUE;
-
-    $schema['block_content_field_data']['unique keys'] += array(
-      'block_content__info' => array('info', 'langcode'),
-    );
-
-    return $schema;
-  }
-
-}
diff -u b/core/modules/block_content/src/BlockContentStorage.php b/core/modules/block_content/src/BlockContentStorage.php
--- b/core/modules/block_content/src/BlockContentStorage.php
+++ b/core/modules/block_content/src/BlockContentStorage.php
@@ -8,6 +8,7 @@
 namespace Drupal\block_content;
 
 use Drupal\Core\Entity\ContentEntityDatabaseStorage;
+use Drupal\Core\Entity\Schema\ContentEntitySchemaHandler;
 
 /**
  * Provides storage for the 'block_content' entity type.
@@ -19,7 +20,16 @@
    */
   protected function schemaHandler() {
     if (!isset($this->schemaHandler)) {
-      $this->schemaHandler = new BlockContentSchemaHandler($this->entityManager, $this->entityType, $this, $this->database);
+      $this->schemaHandler = new ContentEntitySchemaHandler($this->entityManager, $this->entityType, $this, $this->database, function ($schema) {
+        // Marking the respective fields as NOT NULL makes the indexes more
+        // performant.
+        $schema['block_content_field_data']['fields']['info']['not null'] = TRUE;
+
+        $schema['block_content_field_data']['unique keys'] += array(
+          'block_content__info' => array('info', 'langcode'),
+        );
+        return $schema;
+      });
     }
     return $this->schemaHandler;
   }
reverted:
--- b/core/modules/comment/src/CommentSchemaHandler.php
+++ /dev/null
@@ -1,60 +0,0 @@
-<?php
-
-/**
- * @file
- * Contains \Drupal\comment\CommentSchemaHandler.
- */
-
-namespace Drupal\comment;
-
-use Drupal\Core\Entity\ContentEntityTypeInterface;
-use Drupal\Core\Entity\Schema\ContentEntitySchemaHandler;
-
-/**
- * Defines the comment schema handler.
- */
-class CommentSchemaHandler extends ContentEntitySchemaHandler {
-
-  /**
-   * {@inheritdoc}
-   */
-  protected function getEntitySchema(ContentEntityTypeInterface $entity_type, $reset = FALSE) {
-    $schema = parent::getEntitySchema($entity_type, $reset);
-
-    // Marking the respective fields as NOT NULL makes the indexes more
-    // performant.
-    $schema['comment_field_data']['fields']['created']['not null'] = TRUE;
-    $schema['comment_field_data']['fields']['thread']['not null'] = TRUE;
-
-    unset($schema['comment_field_data']['indexes']['comment_field__pid__target_id']);
-    unset($schema['comment_field_data']['indexes']['comment_field__entity_id__target_id']);
-    $schema['comment_field_data']['indexes'] += array(
-      'comment__status_pid' => array('pid', 'status'),
-      'comment__num_new' => array(
-        'entity_id',
-        'entity_type',
-        'comment_type',
-        'status',
-        'created',
-        'cid',
-        'thread',
-      ),
-      'comment__entity_langcode' => array(
-        'entity_id',
-        'entity_type',
-        'comment_type',
-        'default_langcode',
-      ),
-      'comment__created' => array('created'),
-    );
-    $schema['comment_field_data']['foreign keys'] += array(
-      'comment__author' => array(
-        'table' => 'users',
-        'columns' => array('uid' => 'uid'),
-      ),
-    );
-
-    return $schema;
-  }
-
-}
diff -u b/core/modules/comment/src/CommentStorage.php b/core/modules/comment/src/CommentStorage.php
--- b/core/modules/comment/src/CommentStorage.php
+++ b/core/modules/comment/src/CommentStorage.php
@@ -14,6 +14,7 @@
 use Drupal\Core\Entity\EntityInterface;
 use Drupal\Core\Entity\EntityManagerInterface;
 use Drupal\Core\Entity\EntityTypeInterface;
+use Drupal\Core\Entity\Schema\ContentEntitySchemaHandler;
 use Drupal\Core\Session\AccountInterface;
 use Symfony\Component\DependencyInjection\ContainerInterface;
 
@@ -323,7 +324,41 @@
    */
   protected function schemaHandler() {
     if (!isset($this->schemaHandler)) {
-      $this->schemaHandler = new CommentSchemaHandler($this->entityManager, $this->entityType, $this, $this->database);
+      $this->schemaHandler = new ContentEntitySchemaHandler($this->entityManager, $this->entityType, $this, $this->database, function ($schema) {
+        // Marking the respective fields as NOT NULL makes the indexes more
+        // performant.
+        $schema['comment_field_data']['fields']['created']['not null'] = TRUE;
+        $schema['comment_field_data']['fields']['thread']['not null'] = TRUE;
+
+        unset($schema['comment_field_data']['indexes']['comment_field__pid__target_id']);
+        unset($schema['comment_field_data']['indexes']['comment_field__entity_id__target_id']);
+        $schema['comment_field_data']['indexes'] += array(
+          'comment__status_pid' => array('pid', 'status'),
+          'comment__num_new' => array(
+            'entity_id',
+            'entity_type',
+            'comment_type',
+            'status',
+            'created',
+            'cid',
+            'thread',
+          ),
+          'comment__entity_langcode' => array(
+            'entity_id',
+            'entity_type',
+            'comment_type',
+            'default_langcode',
+          ),
+          'comment__created' => array('created'),
+        );
+        $schema['comment_field_data']['foreign keys'] += array(
+          'comment__author' => array(
+            'table' => 'users',
+            'columns' => array('uid' => 'uid'),
+          ),
+        );
+        return $schema;
+      });
     }
     return $this->schemaHandler;
   }
reverted:
--- b/core/modules/file/src/FileSchemaHandler.php
+++ /dev/null
@@ -1,43 +0,0 @@
-<?php
-
-/**
- * @file
- * Contains \Drupal\file\FileSchemaHandler.
- */
-
-namespace Drupal\file;
-
-use Drupal\Core\Entity\ContentEntityTypeInterface;
-use Drupal\Core\Entity\Schema\ContentEntitySchemaHandler;
-
-/**
- * Defines the file schema handler.
- */
-class FileSchemaHandler extends ContentEntitySchemaHandler {
-
-  /**
-   * {@inheritdoc}
-   */
-  protected function getEntitySchema(ContentEntityTypeInterface $entity_type, $reset = FALSE) {
-    $schema = parent::getEntitySchema($entity_type, $reset);
-
-    // Marking the respective fields as NOT NULL makes the indexes more
-    // performant.
-    $schema['file_managed']['fields']['status']['not null'] = TRUE;
-    $schema['file_managed']['fields']['changed']['not null'] = TRUE;
-    $schema['file_managed']['fields']['uri']['not null'] = TRUE;
-
-    // @todo There should be a 'binary' field type or setting.
-    $schema['file_managed']['fields']['uri']['binary'] = TRUE;
-    $schema['file_managed']['indexes'] += array(
-      'file__status' => array('status'),
-      'file__changed' => array('changed'),
-    );
-    $schema['file_managed']['unique keys'] += array(
-      'file__uri' => array('uri'),
-    );
-
-    return $schema;
-  }
-
-}
diff -u b/core/modules/file/src/FileStorage.php b/core/modules/file/src/FileStorage.php
--- b/core/modules/file/src/FileStorage.php
+++ b/core/modules/file/src/FileStorage.php
@@ -8,6 +8,7 @@
 namespace Drupal\file;
 
 use Drupal\Core\Entity\ContentEntityDatabaseStorage;
+use Drupal\Core\Entity\Schema\ContentEntitySchemaHandler;
 
 /**
  * File storage for files.
@@ -32,7 +33,24 @@
    */
   protected function schemaHandler() {
     if (!isset($this->schemaHandler)) {
-      $this->schemaHandler = new FileSchemaHandler($this->entityManager, $this->entityType, $this, $this->database);
+      $this->schemaHandler = new ContentEntitySchemaHandler($this->entityManager, $this->entityType, $this, $this->database, function ($schema) {
+        // Marking the respective fields as NOT NULL makes the indexes more
+        // performant.
+        $schema['file_managed']['fields']['status']['not null'] = TRUE;
+        $schema['file_managed']['fields']['changed']['not null'] = TRUE;
+        $schema['file_managed']['fields']['uri']['not null'] = TRUE;
+
+        // @todo There should be a 'binary' field type or setting.
+        $schema['file_managed']['fields']['uri']['binary'] = TRUE;
+        $schema['file_managed']['indexes'] += array(
+          'file__status' => array('status'),
+          'file__changed' => array('changed'),
+        );
+        $schema['file_managed']['unique keys'] += array(
+          'file__uri' => array('uri'),
+        );
+        return $schema;
+      });
     }
     return $this->schemaHandler;
   }
reverted:
--- b/core/modules/node/src/NodeSchemaHandler.php
+++ /dev/null
@@ -1,64 +0,0 @@
-<?php
-
-/**
- * @file
- * Contains \Drupal\node\NodeSchemaHandler.
- */
-
-namespace Drupal\node;
-
-use Drupal\Core\Entity\ContentEntityTypeInterface;
-use Drupal\Core\Entity\Schema\ContentEntitySchemaHandler;
-
-/**
- * Defines the node schema handler.
- */
-class NodeSchemaHandler extends ContentEntitySchemaHandler {
-
-  /**
-   * {@inheritdoc}
-   */
-  protected function getEntitySchema(ContentEntityTypeInterface $entity_type, $reset = FALSE) {
-    $schema = parent::getEntitySchema($entity_type, $reset);
-
-    // Marking the respective fields as NOT NULL makes the indexes more
-    // performant.
-    $schema['node_field_data']['fields']['changed']['not null'] = TRUE;
-    $schema['node_field_data']['fields']['created']['not null'] = TRUE;
-    $schema['node_field_data']['fields']['default_langcode']['not null'] = TRUE;
-    $schema['node_field_data']['fields']['promote']['not null'] = TRUE;
-    $schema['node_field_data']['fields']['status']['not null'] = TRUE;
-    $schema['node_field_data']['fields']['sticky']['not null'] = TRUE;
-    $schema['node_field_data']['fields']['title']['not null'] = TRUE;
-    $schema['node_field_revision']['fields']['default_langcode']['not null'] = TRUE;
-
-    // @todo Revisit index definitions in https://drupal.org/node/2015277.
-    $schema['node_revision']['indexes'] += array(
-      'node__langcode' => array('langcode'),
-    );
-    $schema['node_revision']['foreign keys'] += array(
-      'node__revision_author' => array(
-        'table' => 'users',
-        'columns' => array('revision_uid' => 'uid'),
-      ),
-    );
-
-    $schema['node_field_data']['indexes'] += array(
-      'node__changed' => array('changed'),
-      'node__created' => array('created'),
-      'node__default_langcode' => array('default_langcode'),
-      'node__langcode' => array('langcode'),
-      'node__frontpage' => array('promote', 'status', 'sticky', 'created'),
-      'node__status_type' => array('status', 'type', 'nid'),
-      'node__title_type' => array('title', array('type', 4)),
-    );
-
-    $schema['node_field_revision']['indexes'] += array(
-      'node__default_langcode' => array('default_langcode'),
-      'node__langcode' => array('langcode'),
-    );
-
-    return $schema;
-  }
-
-}
diff -u b/core/modules/node/src/NodeStorage.php b/core/modules/node/src/NodeStorage.php
--- b/core/modules/node/src/NodeStorage.php
+++ b/core/modules/node/src/NodeStorage.php
@@ -8,6 +8,7 @@
 namespace Drupal\node;
 
 use Drupal\Core\Entity\ContentEntityDatabaseStorage;
+use Drupal\Core\Entity\Schema\ContentEntitySchemaHandler;
 use Drupal\Core\Session\AccountInterface;
 use Drupal\Core\Language\LanguageInterface;
 
@@ -64,7 +65,45 @@
    */
   protected function schemaHandler() {
     if (!isset($this->schemaHandler)) {
-      $this->schemaHandler = new NodeSchemaHandler($this->entityManager, $this->entityType, $this, $this->database);
+      $this->schemaHandler = new ContentEntitySchemaHandler($this->entityManager, $this->entityType, $this, $this->database, function ($schema) {
+        // Marking the respective fields as NOT NULL makes the indexes more
+        // performant.
+        $schema['node_field_data']['fields']['changed']['not null'] = TRUE;
+        $schema['node_field_data']['fields']['created']['not null'] = TRUE;
+        $schema['node_field_data']['fields']['default_langcode']['not null'] = TRUE;
+        $schema['node_field_data']['fields']['promote']['not null'] = TRUE;
+        $schema['node_field_data']['fields']['status']['not null'] = TRUE;
+        $schema['node_field_data']['fields']['sticky']['not null'] = TRUE;
+        $schema['node_field_data']['fields']['title']['not null'] = TRUE;
+        $schema['node_field_revision']['fields']['default_langcode']['not null'] = TRUE;
+
+        // @todo Revisit index definitions in https://drupal.org/node/2015277.
+        $schema['node_revision']['indexes'] += array(
+          'node__langcode' => array('langcode'),
+        );
+        $schema['node_revision']['foreign keys'] += array(
+          'node__revision_author' => array(
+            'table' => 'users',
+            'columns' => array('revision_uid' => 'uid'),
+          ),
+        );
+
+        $schema['node_field_data']['indexes'] += array(
+          'node__changed' => array('changed'),
+          'node__created' => array('created'),
+          'node__default_langcode' => array('default_langcode'),
+          'node__langcode' => array('langcode'),
+          'node__frontpage' => array('promote', 'status', 'sticky', 'created'),
+          'node__status_type' => array('status', 'type', 'nid'),
+          'node__title_type' => array('title', array('type', 4)),
+        );
+
+        $schema['node_field_revision']['indexes'] += array(
+          'node__default_langcode' => array('default_langcode'),
+          'node__langcode' => array('langcode'),
+        );
+        return $schema;
+      });
     }
     return $this->schemaHandler;
   }
reverted:
--- b/core/modules/taxonomy/src/TermSchemaHandler.php
+++ /dev/null
@@ -1,119 +0,0 @@
-<?php
-
-/**
- * @file
- * Contains \Drupal\taxonomy\TermSchemaHandler.
- */
-
-namespace Drupal\taxonomy;
-
-use Drupal\Core\Entity\ContentEntityTypeInterface;
-use Drupal\Core\Entity\Schema\ContentEntitySchemaHandler;
-
-/**
- * Defines the term schema handler.
- */
-class TermSchemaHandler extends ContentEntitySchemaHandler {
-
-  /**
-   * {@inheritdoc}
-   */
-  protected function getEntitySchema(ContentEntityTypeInterface $entity_type, $reset = FALSE) {
-    $schema = parent::getEntitySchema($entity_type, $reset = FALSE);
-
-    if (isset($schema['taxonomy_term_field_data'])) {
-      // Marking the respective fields as NOT NULL makes the indexes more
-      // performant.
-      $schema['taxonomy_term_field_data']['fields']['weight']['not null'] = TRUE;
-      $schema['taxonomy_term_field_data']['fields']['name']['not null'] = TRUE;
-
-      unset($schema['taxonomy_term_field_data']['indexes']['taxonomy_term_field__vid__target_id']);
-      unset($schema['taxonomy_term_field_data']['indexes']['taxonomy_term_field__description__format']);
-      $schema['taxonomy_term_field_data']['indexes'] += array(
-        'taxonomy_term__tree' => array('vid', 'weight', 'name'),
-        'taxonomy_term__vid_name' => array('vid', 'name'),
-        'taxonomy_term__name' => array('name'),
-      );
-    }
-
-    $schema['taxonomy_term_hierarchy'] = array(
-      'description' => 'Stores the hierarchical relationship between terms.',
-      'fields' => array(
-        'tid' => array(
-          'type' => 'int',
-          'unsigned' => TRUE,
-          'not null' => TRUE,
-          'default' => 0,
-          'description' => 'Primary Key: The {taxonomy_term_data}.tid of the term.',
-        ),
-        'parent' => array(
-          'type' => 'int',
-          'unsigned' => TRUE,
-          'not null' => TRUE,
-          'default' => 0,
-          'description' => "Primary Key: The {taxonomy_term_data}.tid of the term's parent. 0 indicates no parent.",
-        ),
-      ),
-      'indexes' => array(
-        'parent' => array('parent'),
-      ),
-      'foreign keys' => array(
-        'taxonomy_term_data' => array(
-          'table' => 'taxonomy_term_data',
-          'columns' => array('tid' => 'tid'),
-        ),
-      ),
-      'primary key' => array('tid', 'parent'),
-    );
-
-    $schema['taxonomy_index'] = array(
-      'description' => 'Maintains denormalized information about node/term relationships.',
-      'fields' => array(
-        'nid' => array(
-          'description' => 'The {node}.nid this record tracks.',
-          'type' => 'int',
-          'unsigned' => TRUE,
-          'not null' => TRUE,
-          'default' => 0,
-        ),
-        'tid' => array(
-          'description' => 'The term ID.',
-          'type' => 'int',
-          'unsigned' => TRUE,
-          'not null' => TRUE,
-          'default' => 0,
-        ),
-        'sticky' => array(
-          'description' => 'Boolean indicating whether the node is sticky.',
-          'type' => 'int',
-          'not null' => FALSE,
-          'default' => 0,
-          'size' => 'tiny',
-        ),
-        'created' => array(
-          'description' => 'The Unix timestamp when the node was created.',
-          'type' => 'int',
-          'not null' => TRUE,
-          'default'=> 0,
-        ),
-      ),
-      'primary key' => array('nid', 'tid'),
-      'indexes' => array(
-        'term_node' => array('tid', 'sticky', 'created'),
-      ),
-      'foreign keys' => array(
-        'tracked_node' => array(
-          'table' => 'node',
-          'columns' => array('nid' => 'nid'),
-        ),
-        'term' => array(
-          'table' => 'taxonomy_term_data',
-          'columns' => array('tid' => 'tid'),
-        ),
-      ),
-    );
-
-    return $schema;
-  }
-
-}
diff -u b/core/modules/taxonomy/src/TermStorage.php b/core/modules/taxonomy/src/TermStorage.php
--- b/core/modules/taxonomy/src/TermStorage.php
+++ b/core/modules/taxonomy/src/TermStorage.php
@@ -10,6 +10,7 @@
 use Drupal\Core\Entity\ContentEntityDatabaseStorage;
 use Drupal\Core\Entity\EntityInterface;
 use Drupal\Core\Entity\Query\QueryInterface;
+use Drupal\Core\Entity\Schema\ContentEntitySchemaHandler;
 
 /**
  * Defines a Controller class for taxonomy terms.
@@ -159,7 +160,98 @@
    */
   protected function schemaHandler() {
     if (!isset($this->schemaHandler)) {
-      $this->schemaHandler = new TermSchemaHandler($this->entityManager, $this->entityType, $this, $this->database);
+      $this->schemaHandler = new ContentEntitySchemaHandler($this->entityManager, $this->entityType, $this, $this->database, function ($schema) {
+        // Marking the respective fields as NOT NULL makes the indexes more
+        // performant.
+        $schema['taxonomy_term_field_data']['fields']['weight']['not null'] = TRUE;
+        $schema['taxonomy_term_field_data']['fields']['name']['not null'] = TRUE;
+
+        unset($schema['taxonomy_term_field_data']['indexes']['taxonomy_term_field__vid__target_id']);
+        unset($schema['taxonomy_term_field_data']['indexes']['taxonomy_term_field__description__format']);
+        $schema['taxonomy_term_field_data']['indexes'] += array(
+          'taxonomy_term__tree' => array('vid', 'weight', 'name'),
+          'taxonomy_term__vid_name' => array('vid', 'name'),
+          'taxonomy_term__name' => array('name'),
+        );
+
+        $schema['taxonomy_term_hierarchy'] = array(
+          'description' => 'Stores the hierarchical relationship between terms.',
+          'fields' => array(
+            'tid' => array(
+              'type' => 'int',
+              'unsigned' => TRUE,
+              'not null' => TRUE,
+              'default' => 0,
+              'description' => 'Primary Key: The {taxonomy_term_data}.tid of the term.',
+            ),
+            'parent' => array(
+              'type' => 'int',
+              'unsigned' => TRUE,
+              'not null' => TRUE,
+              'default' => 0,
+              'description' => "Primary Key: The {taxonomy_term_data}.tid of the term's parent. 0 indicates no parent.",
+            ),
+          ),
+          'indexes' => array(
+            'parent' => array('parent'),
+          ),
+          'foreign keys' => array(
+            'taxonomy_term_data' => array(
+              'table' => 'taxonomy_term_data',
+              'columns' => array('tid' => 'tid'),
+            ),
+          ),
+          'primary key' => array('tid', 'parent'),
+        );
+
+        $schema['taxonomy_index'] = array(
+          'description' => 'Maintains denormalized information about node/term relationships.',
+          'fields' => array(
+            'nid' => array(
+              'description' => 'The {node}.nid this record tracks.',
+              'type' => 'int',
+              'unsigned' => TRUE,
+              'not null' => TRUE,
+              'default' => 0,
+            ),
+            'tid' => array(
+              'description' => 'The term ID.',
+              'type' => 'int',
+              'unsigned' => TRUE,
+              'not null' => TRUE,
+              'default' => 0,
+            ),
+            'sticky' => array(
+              'description' => 'Boolean indicating whether the node is sticky.',
+              'type' => 'int',
+              'not null' => FALSE,
+              'default' => 0,
+              'size' => 'tiny',
+            ),
+            'created' => array(
+              'description' => 'The Unix timestamp when the node was created.',
+              'type' => 'int',
+              'not null' => TRUE,
+              'default'=> 0,
+            ),
+          ),
+          'primary key' => array('nid', 'tid'),
+          'indexes' => array(
+            'term_node' => array('tid', 'sticky', 'created'),
+          ),
+          'foreign keys' => array(
+            'tracked_node' => array(
+              'table' => 'node',
+              'columns' => array('nid' => 'nid'),
+            ),
+            'term' => array(
+              'table' => 'taxonomy_term_data',
+              'columns' => array('tid' => 'tid'),
+            ),
+          ),
+        );
+        return $schema;
+      });
     }
     return $this->schemaHandler;
   }
reverted:
--- b/core/modules/user/src/UserSchemaHandler.php
+++ /dev/null
@@ -1,74 +0,0 @@
-<?php
-
-/**
- * @file
- * Contains \Drupal\user\UserSchemaHandler.
- */
-
-namespace Drupal\user;
-
-use Drupal\Core\Entity\ContentEntityTypeInterface;
-use Drupal\Core\Entity\Schema\ContentEntitySchemaHandler;
-
-/**
- * Defines the user schema handler.
- */
-class UserSchemaHandler extends ContentEntitySchemaHandler {
-
-  /**
-   * {@inheritdoc}
-   */
-  protected function getEntitySchema(ContentEntityTypeInterface $entity_type, $reset = FALSE) {
-    $schema = parent::getEntitySchema($entity_type, $reset);
-
-    // The "users" table does not use serial identifiers.
-    $schema['users']['fields']['uid']['type'] = 'int';
-
-    // Marking the respective fields as NOT NULL makes the indexes more
-    // performant.
-    $schema['users_field_data']['fields']['access']['not null'] = TRUE;
-    $schema['users_field_data']['fields']['created']['not null'] = TRUE;
-    $schema['users_field_data']['fields']['name']['not null'] = TRUE;
-
-    $schema['users_field_data']['indexes'] += array(
-      'user__access' => array('access'),
-      'user__created' => array('created'),
-      'user__mail' => array('mail'),
-    );
-    $schema['users_field_data']['unique keys'] += array(
-      'user__name' => array('name', 'langcode'),
-    );
-
-    $schema['users_roles'] = array(
-      'description' => 'Maps users to roles.',
-      'fields' => array(
-        'uid' => array(
-          'type' => 'int',
-          'unsigned' => TRUE,
-          'not null' => TRUE,
-          'default' => 0,
-          'description' => 'Primary Key: {users}.uid for user.',
-        ),
-        'rid' => array(
-          'type' => 'varchar',
-          'length' => 64,
-          'not null' => TRUE,
-          'description' => 'Primary Key: ID for the role.',
-        ),
-      ),
-      'primary key' => array('uid', 'rid'),
-      'indexes' => array(
-        'rid' => array('rid'),
-      ),
-      'foreign keys' => array(
-        'user' => array(
-          'table' => 'users',
-          'columns' => array('uid' => 'uid'),
-        ),
-      ),
-    );
-
-    return $schema;
-  }
-
-}
diff -u b/core/modules/user/src/UserStorage.php b/core/modules/user/src/UserStorage.php
--- b/core/modules/user/src/UserStorage.php
+++ b/core/modules/user/src/UserStorage.php
@@ -13,6 +13,7 @@
 use Drupal\Core\Entity\EntityInterface;
 use Drupal\Core\Entity\EntityManagerInterface;
 use Drupal\Core\Entity\EntityTypeInterface;
+use Drupal\Core\Entity\Schema\ContentEntitySchemaHandler;
 use Drupal\Core\Password\PasswordInterface;
 use Drupal\Core\Session\AccountInterface;
 use Symfony\Component\DependencyInjection\ContainerInterface;
@@ -154,6 +155,9 @@
     $this->resetCache(array($account->id()));
   }
 
+  /**
+   * {@inheritdoc}
+   */
   public function updateLastAccessTimestamp(AccountInterface $account, $timestamp) {
     $this->database->update('users_field_data')
       ->fields(array(
@@ -170,7 +174,55 @@
    */
   protected function schemaHandler() {
     if (!isset($this->schemaHandler)) {
-      $this->schemaHandler = new UserSchemaHandler($this->entityManager, $this->entityType, $this, $this->database);
+      $this->schemaHandler = new ContentEntitySchemaHandler($this->entityManager, $this->entityType, $this, $this->database, function ($schema) {
+        // The "users" table does not use serial identifiers.
+        $schema['users']['fields']['uid']['type'] = 'int';
+
+        // Marking the respective fields as NOT NULL makes the indexes more
+        // performant.
+        $schema['users_field_data']['fields']['access']['not null'] = TRUE;
+        $schema['users_field_data']['fields']['created']['not null'] = TRUE;
+        $schema['users_field_data']['fields']['name']['not null'] = TRUE;
+
+        $schema['users_field_data']['indexes'] += array(
+          'user__access' => array('access'),
+          'user__created' => array('created'),
+          'user__mail' => array('mail'),
+        );
+        $schema['users_field_data']['unique keys'] += array(
+          'user__name' => array('name', 'langcode'),
+        );
+
+        $schema['users_roles'] = array(
+          'description' => 'Maps users to roles.',
+          'fields' => array(
+            'uid' => array(
+              'type' => 'int',
+              'unsigned' => TRUE,
+              'not null' => TRUE,
+              'default' => 0,
+              'description' => 'Primary Key: {users}.uid for user.',
+            ),
+            'rid' => array(
+              'type' => 'varchar',
+              'length' => 64,
+              'not null' => TRUE,
+              'description' => 'Primary Key: ID for the role.',
+            ),
+          ),
+          'primary key' => array('uid', 'rid'),
+          'indexes' => array(
+            'rid' => array('rid'),
+          ),
+          'foreign keys' => array(
+            'user' => array(
+              'table' => 'users',
+              'columns' => array('uid' => 'uid'),
+            ),
+          ),
+        );
+        return $schema;
+      });
     }
     return $this->schemaHandler;
   }
only in patch2:
unchanged:
--- a/core/lib/Drupal/Core/Entity/ContentEntityDatabaseStorage.php
+++ b/core/lib/Drupal/Core/Entity/ContentEntityDatabaseStorage.php
@@ -234,7 +234,7 @@ public function getSchema() {
    */
   protected function schemaHandler() {
     if (!isset($this->schemaHandler)) {
-      $this->schemaHandler = new ContentEntitySchemaHandler($this->entityManager, $this->entityType, $this);
+      $this->schemaHandler = new ContentEntitySchemaHandler($this->entityManager, $this->entityType, $this, $this->database);
     }
     return $this->schemaHandler;
   }