diff --git a/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/BooleanItem.php b/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/BooleanItem.php
index 2d242a4..1d9884f 100644
--- a/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/BooleanItem.php
+++ b/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/BooleanItem.php
@@ -52,6 +52,7 @@ public static function schema(FieldDefinitionInterface $field_definition) {
         'value' => array(
           'type' => 'int',
           'size' => 'tiny',
+          'not null' => TRUE,
         ),
       ),
     );
diff --git a/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/DateItem.php b/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/DateItem.php
index 1082af3..c1276dd 100644
--- a/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/DateItem.php
+++ b/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/DateItem.php
@@ -52,9 +52,9 @@ public static function schema(FieldDefinitionInterface $field_definition) {
     return array(
       'columns' => array(
         'value' => array(
-          'type' => 'int',
-          // @todo Needs a size. What kind of value do we store here anyway, a
-          // timestamp?
+          'type' => 'varchar',
+          'length' => 20,
+          'not null' => FALSE,
         ),
       ),
     );
diff --git a/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/EmailItem.php b/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/EmailItem.php
index b419507..aee1a4a 100644
--- a/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/EmailItem.php
+++ b/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/EmailItem.php
@@ -53,6 +53,7 @@ public static function schema(FieldDefinitionInterface $field_definition) {
         'value' => array(
           'type' => 'varchar',
           'length' => EMAIL_MAX_LENGTH,
+          'not null' => FALSE,
         ),
       ),
     );
diff --git a/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/FloatItem.php b/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/FloatItem.php
index 0ca6d0f..045af1c 100644
--- a/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/FloatItem.php
+++ b/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/FloatItem.php
@@ -52,6 +52,7 @@ public static function schema(FieldDefinitionInterface $field_definition) {
       'columns' => array(
         'value' => array(
           'type' => 'float',
+          'not null' => FALSE,
         ),
       ),
     );
diff --git a/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/IntegerItem.php b/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/IntegerItem.php
index 23bb1ad..ec49cdb 100644
--- a/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/IntegerItem.php
+++ b/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/IntegerItem.php
@@ -52,6 +52,7 @@ public static function schema(FieldDefinitionInterface $field_definition) {
       'columns' => array(
         'value' => array(
           'type' => 'int',
+          'not null' => TRUE,
         ),
       ),
     );
diff --git a/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/LanguageItem.php b/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/LanguageItem.php
index 1456b80..3bae65b 100644
--- a/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/LanguageItem.php
+++ b/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/LanguageItem.php
@@ -65,6 +65,7 @@ public static function schema(FieldDefinitionInterface $field_definition) {
         'value' => array(
           'type' => 'varchar',
           'length' => 12,
+          'not null' => FALSE,
         ),
       ),
     );
diff --git a/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/StringItem.php b/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/StringItem.php
index feb5bd7..ce78a40 100644
--- a/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/StringItem.php
+++ b/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/StringItem.php
@@ -55,7 +55,8 @@ public static function schema(FieldDefinitionInterface $field_definition) {
       'columns' => array(
         'value' => array(
           'type' => 'varchar',
-          'length' => $field_definition->getFieldSetting('max_length'),
+          'length' => $field_definition->getSetting('max_length'),
+          'not null' => FALSE,
         ),
       ),
     );
diff --git a/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/UriItem.php b/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/UriItem.php
index dc118a7..4cad163 100644
--- a/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/UriItem.php
+++ b/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/UriItem.php
@@ -51,6 +51,7 @@ public static function schema(FieldDefinitionInterface $field_definition) {
       'columns' => array(
         'value' => array(
           'type' => 'text',
+          'not null' => TRUE,
         ),
       ),
     );
diff --git a/core/modules/field/lib/Drupal/field/Entity/Field.php b/core/modules/field/lib/Drupal/field/Entity/Field.php
index c3fd8cd..e1f89e2 100644
--- a/core/modules/field/lib/Drupal/field/Entity/Field.php
+++ b/core/modules/field/lib/Drupal/field/Entity/Field.php
@@ -178,6 +178,13 @@ class Field extends ConfigEntityBase implements FieldInterface {
   public $deleted = FALSE;
 
   /**
+   * The field schema.
+   *
+   * @var array
+   */
+  protected $schema;
+
+  /**
    * The original field.
    *
    * @var \Drupal\field\Entity\Field
diff --git a/core/modules/system/system.module b/core/modules/system/system.module
index b6d4e2b..a9187b2 100644
--- a/core/modules/system/system.module
+++ b/core/modules/system/system.module
@@ -7,7 +7,6 @@
 
 use Drupal\Core\Cache\CacheBackendInterface;
 use Drupal\Core\Cache\Cache;
-use Drupal\Core\Field\Plugin\Field\FieldType\EmailItem;
 use Drupal\Core\Language\Language;
 use Drupal\Core\Utility\ModuleInfo;
 use Drupal\user\UserInterface;
diff --git a/core/modules/text/lib/Drupal/text/Plugin/Field/FieldType/TextItem.php b/core/modules/text/lib/Drupal/text/Plugin/Field/FieldType/TextItem.php
index 2fbec6c..bf415c5 100644
--- a/core/modules/text/lib/Drupal/text/Plugin/Field/FieldType/TextItem.php
+++ b/core/modules/text/lib/Drupal/text/Plugin/Field/FieldType/TextItem.php
@@ -36,7 +36,7 @@ public static function schema(FieldDefinitionInterface $field_definition) {
       'columns' => array(
         'value' => array(
           'type' => 'varchar',
-          'length' => $field_definition->settings['max_length'],
+          'length' => $field_definition->getSetting('max_length'),
           'not null' => FALSE,
         ),
         'format' => array(