From 634379299f7ab35bf64504718a77d00767fa2dfa Mon Sep 17 00:00:00 2001
From: Dries Buytaert <dries@buytaert.net>
Date: Sun, 4 Jan 2009 19:56:51 +0000
Subject: - Patch #320591 by Moshe, Crell et al: tag specific alter hook for
 database queries.

---
 modules/system/system.api.php | 62 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 62 insertions(+)

(limited to 'modules/system/system.api.php')

diff --git a/modules/system/system.api.php b/modules/system/system.api.php
index 3ac517fd4..e6d3b3038 100644
--- a/modules/system/system.api.php
+++ b/modules/system/system.api.php
@@ -1374,6 +1374,68 @@ function hook_schema_alter(&$schema) {
   );
 }
 
+/**
+ * Perform alterations to a structured query.
+ *
+ * Structured (aka dynamic) queries that have tags associated may be altered by any module
+ * before the query is executed.
+ *
+ * @see hook_query_TAG_alter()
+ * @see node_query_node_access_alter()
+ * 
+ * @param $query
+ *   A Query object describing the composite parts of a SQL query.
+ * @return
+ *   None.
+ */
+function hook_query_alter(QueryAlterableInterface $query) {
+  
+}
+
+/**
+ * Perform alterations to a structured query for a given tag.
+ *
+ * @see hook_query_alter()
+ * @see node_query_node_access_alter()
+ * 
+ * @param $query
+ *   An Query object describing the composite parts of a SQL query.
+ * @return
+ *   None.
+ */
+function hook_query_TAG_alter(QueryAlterableInterface $query) {
+  // Skip the extra expensive alterations if site has no node access control modules.
+  if (!node_access_view_all_nodes()) {
+    // Prevent duplicates records.
+    $query->distinct();
+    // The recognized operations are 'view', 'update', 'delete'.
+    if (!$op = $query->getMetaData('op')) {
+      $op = 'view';
+    }
+    // Skip the extra joins and conditions for node admins.
+    if (!user_access('bypass node access')) {
+      // The node_access table has the access grants for any given node.
+      $access_alias = $query->join('node_access', 'na', 'na.nid = n.nid');
+      $or = db_or();
+      // If any grant exists for the specified user, then user has access to the node for the specified operation.
+      foreach (node_access_grants($op, $query->getMetaData('account')) as $realm => $gids) {
+        foreach ($gids as $gid) {
+          $or->condition(db_and()
+            ->condition("{$access_alias}.gid", $gid)
+            ->condition("{$access_alias}.realm", $realm)
+          );
+        }
+      }
+
+      if (count($or->conditions())) {
+        $query->condition($or);
+      }
+      
+      $query->condition("{$access_alias}.grant_$op", 1, '>=');
+    }
+  }
+}
+
 /**
  * Install the current version of the database schema, and any other setup tasks.
  *
-- 
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