diff --git a/core/includes/bootstrap.inc b/core/includes/bootstrap.inc
index 0b1f633..1d8a746 100644
--- a/core/includes/bootstrap.inc
+++ b/core/includes/bootstrap.inc
@@ -10,6 +10,7 @@
 use Drupal\Component\Utility\Html;
 use Drupal\Component\Utility\SafeMarkup;
 use Drupal\Component\Utility\Unicode;
+use Drupal\Core\Database\Database;
 use Drupal\Core\DrupalKernel;
 use Drupal\Core\Extension\ExtensionDiscovery;
 use Drupal\Core\Logger\RfcLogLevel;
@@ -758,6 +759,22 @@ function drupal_installation_attempted() {
 }
 
 /**
+ * Check whether Drupal is installed.
+ *
+ * @return bool
+ *   TRUE if Drupal is installed, FALSE otherwise.
+ */
+function drupal_is_installed() {
+  // Check that a default database connection has been defined.
+  if (!Database::getConnectionInfo()) {
+    return FALSE;
+  }
+
+  // Check whether the sessions table exists.
+  return Database::getConnection()->schema()->tableExists('sessions');
+}
+
+/**
  * Gets the name of the currently active installation profile.
  *
  * When this function is called during Drupal's initial installation process,
diff --git a/core/includes/install.core.inc b/core/includes/install.core.inc
index 890f7be..86130ba 100644
--- a/core/includes/install.core.inc
+++ b/core/includes/install.core.inc
@@ -1096,14 +1096,8 @@ function install_verify_database_settings($site_path) {
  * Verify that the database is ready (no existing Drupal installation).
  */
 function install_verify_database_ready() {
-  $system_schema = system_schema();
-  end($system_schema);
-  $table = key($system_schema);
-
-  if ($database = Database::getConnectionInfo()) {
-    if (Database::getConnection()->schema()->tableExists($table)) {
-      throw new AlreadyInstalledException(\Drupal::service('string_translation'));
-    }
+  if (drupal_is_installed()) {
+    throw new AlreadyInstalledException(\Drupal::service('string_translation'));
   }
 }
 
diff --git a/core/lib/Drupal/Core/DrupalKernel.php b/core/lib/Drupal/Core/DrupalKernel.php
index 2ddc3ee..8a9000d 100644
--- a/core/lib/Drupal/Core/DrupalKernel.php
+++ b/core/lib/Drupal/Core/DrupalKernel.php
@@ -13,7 +13,7 @@
 use Drupal\Component\Utility\UrlHelper;
 use Drupal\Core\Config\BootstrapConfigStorageFactory;
 use Drupal\Core\Config\NullStorage;
-use Drupal\Core\Database\Database;
+use Drupal\Core\Database\DatabaseException;
 use Drupal\Core\DependencyInjection\ContainerBuilder;
 use Drupal\Core\DependencyInjection\ServiceModifierInterface;
 use Drupal\Core\DependencyInjection\ServiceProviderInterface;
@@ -129,6 +129,13 @@ class DrupalKernel implements DrupalKernelInterface, TerminableInterface {
   protected $prepared = FALSE;
 
   /**
+   * Whether the user should be redirected to the installer.
+   *
+   * @var bool|null
+   */
+  protected $needInstallRedirect;
+
+  /**
    * Holds the list of enabled modules.
    *
    * @var array
@@ -628,10 +635,7 @@ public function handle(Request $request, $type = self::MASTER_REQUEST, $catch =
     try {
       $this->initializeSettings($request);
 
-      // Redirect the user to the installation script if Drupal has not been
-      // installed yet (i.e., if no $databases array has been defined in the
-      // settings.php file) and we are not already installing.
-      if (!Database::getConnectionInfo() && !drupal_installation_attempted() && PHP_SAPI !== 'cli') {
+      if ($this->needInstallRedirect()) {
         $response = new RedirectResponse($request->getBasePath() . '/core/install.php');
       }
       else {
@@ -654,6 +658,33 @@ public function handle(Request $request, $type = self::MASTER_REQUEST, $catch =
   }
 
   /**
+   * Check whether we should redirect to the installer (core/install.php).
+   *
+   * This would be the case if Drupal is not already installed, if we are not
+   * already in the process of installation, and this is not being called on the
+   * command line.
+   *
+   * @return bool
+   *   TRUE if the user should be redirected, FALSE otherwise.
+   */
+  protected function needInstallRedirect() {
+    if (!isset($this->needInstallRedirect)) {
+      try {
+        $this->needInstallRedirect = !drupal_installation_attempted()
+          && PHP_SAPI !== 'cli'
+          && !drupal_is_installed();
+      }
+      catch (DatabaseException $e) {
+        // Ignore database errors: they could have many causes, and would not
+        // indicate that Drupal is not installed.
+        $this->needInstallRedirect = FALSE;
+      }
+    }
+
+    return $this->needInstallRedirect;
+  }
+
+  /**
    * Converts an exception into a response.
    *
    * @param \Exception $e