diff -u b/core/lib/Drupal/Core/Cache/CachetagSchema.php b/core/lib/Drupal/Core/Cache/CachetagSchema.php
--- b/core/lib/Drupal/Core/Cache/CachetagSchema.php
+++ b/core/lib/Drupal/Core/Cache/CachetagSchema.php
@@ -9,6 +9,12 @@
 
 use Drupal\Core\Database\SchemaProviderInterface;
 
+/**
+ * Class providing schema for the {cachetags} table.
+ *
+ * One SchemaProviderInterface class can provide only one table but cache works
+ * with two.
+ */
 class CachetagSchema implements SchemaProviderInterface {
 
   /**
diff -u b/core/lib/Drupal/Core/Cache/DatabaseBackend.php b/core/lib/Drupal/Core/Cache/DatabaseBackend.php
--- b/core/lib/Drupal/Core/Cache/DatabaseBackend.php
+++ b/core/lib/Drupal/Core/Cache/DatabaseBackend.php
@@ -409,6 +409,7 @@
         if ($this->connection->schema()->tableExists('cachetags')) {
           throw $e;
         }
+        // The table does not exist yet so there are no db tags.
         $db_tags = array();
       }
       $tag_cache += $db_tags;
diff -u b/core/lib/Drupal/Core/Database/Query/Query.php b/core/lib/Drupal/Core/Database/Query/Query.php
--- b/core/lib/Drupal/Core/Database/Query/Query.php
+++ b/core/lib/Drupal/Core/Database/Query/Query.php
@@ -9,7 +9,6 @@
 
 use Drupal\Core\Database\Database;
 use Drupal\Core\Database\Connection;
-use Drupal\Core\Database\SchemaObjectExistsException;
 use Drupal\Core\Database\SchemaProviderInterface;
 
 /**
@@ -23,7 +22,9 @@
   /**
    * The base table.
    *
-   * @var string
+   * Can be a Query object for subqueries.
+   *
+   * @var string|static
    */
   protected $table;
 
@@ -137,13 +138,8 @@
       return $this->execute();
     }
     catch (\Exception $e) {
-      // Resolve count queries.
-      $table = $this->table;
-      while ($table instanceof Query) {
-        $table = $table->getTable();
-      }
       // If there was an exception, try to create the table.
-      if ($this->connection->schema()->ensureTableExists($table, $schema_provider)) {
+      if ($this->connection->schema()->ensureTableExists($this->getTable(), $schema_provider)) {
         return $this->execute();
       }
       // Some other failure that we can not recover from.
@@ -151,8 +147,19 @@
     }
   }
 
+  /**
+   * Returns the base table.
+   *
+   * @return string
+   *   The base table. If the base table is a subquery then the base table of
+   *   that query. This was even for count queries the base table is returned.
+   */
   public function getTable() {
-    return $this->table;
+    $table = $this->table;
+    while ($table instanceof Query) {
+      $table = $table->getTable();
+    }
+    return $table;
   }
 
   /**
diff -u b/core/lib/Drupal/Core/Database/SchemaProviderInterface.php b/core/lib/Drupal/Core/Database/SchemaProviderInterface.php
--- b/core/lib/Drupal/Core/Database/SchemaProviderInterface.php
+++ b/core/lib/Drupal/Core/Database/SchemaProviderInterface.php
@@ -22,6 +22,9 @@
    * A schema API array.
    *
    * @return array
+   *   A schema API array
+   *
+   * @see hook_schema()
    */
   public function getSchema();
 }
diff -u b/core/modules/system/src/Tests/Database/SelectTest.php b/core/modules/system/src/Tests/Database/SelectTest.php
--- b/core/modules/system/src/Tests/Database/SelectTest.php
+++ b/core/modules/system/src/Tests/Database/SelectTest.php
@@ -29,9 +29,9 @@
   }
 
   /**
-   * Tests rudimentary SELECT statements.
+   * Tests rudimentary SELECT statements with table dropping and recreation.
    */
-  function testSimpleSelectWithTableAssert() {
+  function testSimpleSelectWithEnsuringTable() {
     db_drop_table('test');
     $query = db_select('test');
     $query->addField('test', 'name');
only in patch2:
unchanged:
--- a/core/modules/system/src/Tests/Cache/DatabaseBackendTagTest.php
+++ b/core/modules/system/src/Tests/Cache/DatabaseBackendTagTest.php
@@ -8,6 +8,7 @@
 namespace Drupal\system\Tests\Cache;
 
 use Drupal\Core\Cache\Cache;
+use Drupal\Core\Database\Database;
 use Drupal\Core\DependencyInjection\ContainerBuilder;
 use Drupal\simpletest\DrupalUnitTestBase;
 use Symfony\Component\DependencyInjection\Reference;
@@ -48,7 +49,7 @@ public function testTagInvalidations() {
       $this->assertTrue($bin->get('test'), 'Cache item was set in bin.');
     }
 
-    $invalidations_before = intval(db_select('cachetags')->fields('cachetags', array('invalidations'))->condition('tag', 'test_tag:2')->execute()->fetchField());
+    $this->assertFalse(Database::getConnection()->schema()->tableExists('cachetags'));
     Cache::invalidateTags(array('test_tag:2'));
 
     // Test that cache entry has been invalidated in multiple bins.
@@ -59,7 +60,7 @@ public function testTagInvalidations() {
 
     // Test that only one tag invalidation has occurred.
     $invalidations_after = intval(db_select('cachetags')->fields('cachetags', array('invalidations'))->condition('tag', 'test_tag:2')->execute()->fetchField());
-    $this->assertEqual($invalidations_after, $invalidations_before + 1, 'Only one addition cache tag invalidation has occurred after invalidating a tag used in multiple bins.');
+    $this->assertEqual($invalidations_after, 1, 'Only one addition cache tag invalidation has occurred after invalidating a tag used in multiple bins.');
   }
 
   public function testTagDeletions() {
@@ -72,7 +73,7 @@ public function testTagDeletions() {
       $this->assertTrue($bin->get('test'), 'Cache item was set in bin.');
     }
 
-    $deletions_before = intval(db_select('cachetags')->fields('cachetags', array('deletions'))->condition('tag', 'test_tag:2')->execute()->fetchField());
+    $this->assertFalse(Database::getConnection()->schema()->tableExists('cachetags'));
     Cache::deleteTags(array('test_tag:2'));
 
     // Test that cache entry has been deleted in multiple bins.
@@ -83,7 +84,7 @@ public function testTagDeletions() {
 
     // Test that only one tag deletion has occurred.
     $deletions_after = intval(db_select('cachetags')->fields('cachetags', array('deletions'))->condition('tag', 'test_tag:2')->execute()->fetchField());
-    $this->assertEqual($deletions_after, $deletions_before + 1, 'Only one addition cache tag deletion has occurred after deleting a tag used in multiple bins.');
+    $this->assertEqual($deletions_after, 1, 'Only one addition cache tag deletion has occurred after deleting a tag used in multiple bins.');
   }
 
 }