diff --git a/core/lib/Drupal/Core/Entity/Sql/DefaultTableMapping.php b/core/lib/Drupal/Core/Entity/Sql/DefaultTableMapping.php
index 920adc1..8c9d9f4 100644
--- a/core/lib/Drupal/Core/Entity/Sql/DefaultTableMapping.php
+++ b/core/lib/Drupal/Core/Entity/Sql/DefaultTableMapping.php
@@ -620,11 +620,14 @@ protected function generateFieldTableName(FieldStorageDefinitionInterface $stora
 
       $table_name = $this->prefix . $entity_type_id . $separator . $field_hash;
 
-      // If the resulting table name is still longer than 48 characters, use a
-      // simple "prefix + field_hash" name instead.
+      // If the resulting table name is still longer than 48 characters, use the
+      // following pattern:
+      // - prefix: max 34 chars;
+      // - separator: max 4 chars;
+      // - field_hash: max 10 chars.
       if (strlen($table_name) > 48) {
-        $prefix = substr($this->prefix, 0, 38);
-        $table_name = $prefix . $field_hash;
+        $prefix = substr($this->prefix, 0, 34);
+        $table_name = $prefix . $separator . $field_hash;
       }
     }
     return $table_name;
diff --git a/core/lib/Drupal/Core/Entity/Sql/SqlContentEntityStorageSchemaConverter.php b/core/lib/Drupal/Core/Entity/Sql/SqlContentEntityStorageSchemaConverter.php
index fc1874c..7d8f53b 100644
--- a/core/lib/Drupal/Core/Entity/Sql/SqlContentEntityStorageSchemaConverter.php
+++ b/core/lib/Drupal/Core/Entity/Sql/SqlContentEntityStorageSchemaConverter.php
@@ -149,8 +149,8 @@ public function convertToRevisionable(array &$sandbox, array $fields_to_update =
 
       // Rename the original tables so we can put them back in place in case
       // anything goes wrong.
-      $backup_table_name_mapping = array_combine($sandbox['original_table_mapping']->getTableNames(), $sandbox['backup_table_mapping']->getTableNames());
-      foreach ($backup_table_name_mapping as $original_table_name => $backup_table_name) {
+      $backup_table_names = array_combine($sandbox['original_table_mapping']->getTableNames(), $sandbox['backup_table_mapping']->getTableNames());
+      foreach ($backup_table_names as $original_table_name => $backup_table_name) {
         $this->database->schema()->renameTable($original_table_name, $backup_table_name);
       }
 
@@ -197,7 +197,7 @@ public function convertToRevisionable(array &$sandbox, array $fields_to_update =
       }
       catch (\Exception $e) {
         // Something went wrong, bring back the original tables.
-        foreach ($backup_table_name_mapping as $original_table_name => $backup_table_name) {
+        foreach ($backup_table_names as $original_table_name => $backup_table_name) {
           // We are in the 'original data recovery' phase, so we need to be sure
           // that the initial tables can be properly restored.
           if ($this->database->schema()->tableExists($original_table_name)) {
@@ -214,7 +214,7 @@ public function convertToRevisionable(array &$sandbox, array $fields_to_update =
       // At this point the update process either finished successfully or any
       // error has been handled already, so we can drop the backup entity
       // tables.
-      foreach ($backup_table_name_mapping as $original_table_name => $backup_table_name) {
+      foreach ($backup_table_names as $original_table_name => $backup_table_name) {
         $this->database->schema()->dropTable($backup_table_name);
       }
     }
diff --git a/core/tests/Drupal/Tests/Core/Entity/Sql/DefaultTableMappingTest.php b/core/tests/Drupal/Tests/Core/Entity/Sql/DefaultTableMappingTest.php
index e9a306d..b3f317c 100644
--- a/core/tests/Drupal/Tests/Core/Entity/Sql/DefaultTableMappingTest.php
+++ b/core/tests/Drupal/Tests/Core/Entity/Sql/DefaultTableMappingTest.php
@@ -4,6 +4,7 @@
 
 use Drupal\Core\Entity\Sql\DefaultTableMapping;
 use Drupal\Core\Entity\Sql\SqlContentEntityStorageException;
+use Drupal\Core\Entity\Sql\TemporaryTableMapping;
 use Drupal\Tests\UnitTestCase;
 
 /**
@@ -445,6 +446,142 @@ public function testGetFieldTableNameInvalid() {
   }
 
   /**
+   * @covers ::getDedicatedDataTableName
+   * @covers ::getDedicatedRevisionTableName
+   *
+   * @dataProvider providerTestGetDedicatedTableName
+   */
+  public function testGetDedicatedTableName($info, $expected_data_table, $expected_revision_table) {
+    $entity_type_id = $info['entity_type_id'];
+    $field_name = $info['field_name'];
+
+    $definition = $this->setUpDefinition($field_name, []);
+    $definition->expects($this->any())
+      ->method('getTargetEntityTypeId')
+      ->will($this->returnValue($entity_type_id));
+    $definition->expects($this->any())
+      ->method('getUniqueStorageIdentifier')
+      ->will($this->returnValue($entity_type_id . '-' . $field_name));
+
+    $this->entityType
+      ->expects($this->any())
+      ->method('getBaseTable')
+      ->willReturn($info['entity_type_id']);
+    $this->entityType
+      ->expects($this->any())
+      ->method('isTranslatable')
+      ->willReturn(FALSE);
+    $this->entityType
+      ->expects($this->any())
+      ->method('isRevisionable')
+      ->willReturn(FALSE);
+
+    $table_mapping = new DefaultTableMapping($this->entityType, [], $info['prefix']);
+
+    $this->assertSame($expected_data_table, $table_mapping->getDedicatedDataTableName($definition));
+    $this->assertSame($expected_revision_table, $table_mapping->getDedicatedRevisionTableName($definition));
+  }
+
+  /**
+   * Provides test data for testGetDedicatedTableName().
+   *
+   * @return array[]
+   *   A nested array where each inner array has the following values: an array
+   *   consisting of the entity type ID, field name and a table prefix, followed
+   *   by the expected data table name and the revision table name.
+   */
+  public function providerTestGetDedicatedTableName() {
+    $data = [];
+
+    $data['short entity type; short field name; no prefix'] = [
+      [
+        'entity_type_id' => 'short_entity_type',
+        'field_name' => 'short_field_name',
+        'prefix' => '',
+      ],
+      'short_entity_type__short_field_name',
+      'short_entity_type_revision__short_field_name',
+    ];
+    $data['short entity type; long field name; no prefix'] = [
+      [
+        'entity_type_id' => 'short_entity_type',
+        'field_name' => 'long_field_name_abcdefghijklmnopqrstuvwxyz',
+        'prefix' => '',
+      ],
+      'short_entity_type__28a01c7777',
+      'short_entity_type_r__28a01c7777',
+    ];
+    $data['long entity type; short field name; no prefix'] = [
+      [
+        'entity_type_id' => 'long_entity_type_abcdefghijklmnopqrstuvwxyz',
+        'field_name' => 'short_field_name',
+        'prefix' => '',
+      ],
+      'long_entity_type_abcdefghijklmno__a526e4e042',
+      'long_entity_type_abcdefghijklmno_r__a526e4e042',
+    ];
+    $data['long entity type; long field name; no prefix'] = [
+      [
+        'entity_type_id' => 'long_entity_type_abcdefghijklmnopqrstuvwxyz',
+        'field_name' => 'long_field_name_abcdefghijklmnopqrstuvwxyz',
+        'prefix' => '',
+      ],
+      'long_entity_type_abcdefghijklmno__7705d52d75',
+      'long_entity_type_abcdefghijklmno_r__7705d52d75',
+    ];
+
+    $data['short entity type; short field name; with prefix'] = [
+      [
+        'entity_type_id' => 'short_entity_type',
+        'field_name' => 'short_field_name',
+        'prefix' => 'prefix_',
+      ],
+      'prefix_short_entity_type__short_field_name',
+      'prefix_short_entity_type_r__a133cc765a',
+    ];
+    $data['short entity type; long field name; with prefix'] = [
+      [
+        'entity_type_id' => 'short_entity_type',
+        'field_name' => 'long_field_name_abcdefghijklmnopqrstuvwxyz',
+        'prefix' => 'prefix_',
+      ],
+      'prefix_short_entity_type__28a01c7777',
+      'prefix_short_entity_type_r__28a01c7777',
+    ];
+    $data['long entity type; short field name; with prefix'] = [
+      [
+        'entity_type_id' => 'long_entity_type_abcdefghijklmnopqrstuvwxyz',
+        'field_name' => 'short_field_name',
+        'prefix' => 'prefix_',
+      ],
+      'prefix___a526e4e042',
+      'prefix__r__a526e4e042',
+    ];
+    $data['long entity type; long field name; with prefix'] = [
+      [
+        'entity_type_id' => 'long_entity_type_abcdefghijklmnopqrstuvwxyz',
+        'field_name' => 'long_field_name_abcdefghijklmnopqrstuvwxyz',
+        'prefix' => 'prefix_',
+      ],
+      'prefix___7705d52d75',
+      'prefix__r__7705d52d75',
+    ];
+
+    return $data;
+  }
+
+  /**
+   * @coversDefaultClass \Drupal\Core\Entity\Sql\TemporaryTableMapping
+   *
+   * @expectedDeprecation Drupal\Core\Entity\Sql\TemporaryTableMapping is deprecated in Drupal 8.6.x and will be removed before Drupal 9.0.0. Use the default table mapping with a prefix instead.
+   * @group legacy
+   */
+  public function testTemporaryTableMapping() {
+    $table_mapping = new TemporaryTableMapping($this->entityType, [], '');
+    $this->assertTrue($table_mapping instanceof DefaultTableMapping);
+  }
+
+  /**
    * Sets up a field storage definition for the test.
    *
    * @param string $name