Issue #911352 by Liam Morland, Sylvain Lecoy, Joe Murray, Crell: Document that foreign keys may not be used by all drivers

1 files changed, 5 insertions, 1 deletions

diff --git a/modules/system/system.api.php b/modules/system/system.api.php
index 3f61cc0e8..4576f8197 100644
--- a/modules/system/system.api.php
+++ b/modules/system/system.api.php
@@ -3175,7 +3175,9 @@ function hook_requirements($phase) {
  * creation and alteration of the supported database engines.
  *
  * See the Schema API Handbook at http://drupal.org/node/146843 for details on
- * schema definition structures.
+ * schema definition structures. Note that foreign key definitions are for
+ * documentation purposes only; foreign keys are not created in the database,
+ * nor are they enforced by Drupal.
  *
  * @return array
  *   A schema definition structure array. For each element of the
@@ -3227,6 +3229,8 @@ function hook_schema() {
       'nid_vid' => array('nid', 'vid'),
       'vid'     => array('vid'),
     ),
+    // For documentation purposes only; foreign keys are not created in the
+    // database.
     'foreign keys' => array(
       'node_revision' => array(
         'table' => 'node_revision',