diff --git database/select.inc database/select.inc
index 67a5583..7b83c7a 100644
--- database/select.inc
+++ database/select.inc
@@ -1162,7 +1162,7 @@ class SelectQuery extends Query implements SelectQueryInterface {
       foreach ($this->alterTags as $tag => $value) {
         $hooks[] = 'query_' . $tag;
       }
-      drupal_alter($hooks, $query);
+      dbtng_drupal_alter($hooks, $query);
     }
 
     $this->prepared = TRUE;
diff --git dbtng.module dbtng.module
index a49d9ab..d8d91c4 100644
--- dbtng.module
+++ dbtng.module
@@ -831,4 +831,88 @@ function drupal_get_query_parameters(array $query = NULL, array $exclude = array
 
 /**
  * @} End of "defgroup dbtng".
- */
\ No newline at end of file
+ */
+
+/**
+ * Backport of D7's drupal_alter(), which allows hook_query_alter() and
+ * hook_query_TAG_alter() to work properly.
+ */
+function dbtng_drupal_alter($type, &$data, &$context1 = NULL, &$context2 = NULL) {
+  // Use the advanced drupal_static() pattern, since this is called very often.
+  static $drupal_static_fast;
+  if (!isset($drupal_static_fast)) {
+    $drupal_static_fast['functions'] = NULL;
+  }
+  $functions = &$drupal_static_fast['functions'];
+
+  // Most of the time, $type is passed as a string, so for performance,
+  // normalize it to that. When passed as an array, usually the first item in
+  // the array is a generic type, and additional items in the array are more
+  // specific variants of it, as in the case of array('form', 'form_FORM_ID').
+  if (is_array($type)) {
+    $cid = implode(',', $type);
+    $extra_types = $type;
+    $type = array_shift($extra_types);
+    // Allow if statements in this function to use the faster isset() rather
+    // than !empty() both when $type is passed as a string, or as an array with
+    // one item.
+    if (empty($extra_types)) {
+      unset($extra_types);
+    }
+  }
+  else {
+    $cid = $type;
+  }
+
+
+  // Some alter hooks are invoked many times per page request, so statically
+  // cache the list of functions to call, and on subsequent calls, iterate
+  // through them quickly.
+  if (!isset($functions[$cid])) {
+    $functions[$cid] = array();
+    $hook = $type . '_alter';
+    $modules = module_implements($hook);
+    if (!isset($extra_types)) {
+      // For the more common case of a single hook, we do not need to call
+      // function_exists(), since module_implements() returns only modules with
+      // implementations.
+      foreach ($modules as $module) {
+        $functions[$cid][] = $module . '_' . $hook;
+      }
+    }
+    else {
+      // For multiple hooks, we need $modules to contain every module that
+      // implements at least one of them.
+      $extra_modules = array();
+      foreach ($extra_types as $extra_type) {
+        $extra_modules = array_merge($extra_modules, module_implements($extra_type . '_alter'));
+      }
+      // If any modules implement one of the extra hooks that do not implement
+      // the primary hook, we need to add them to the $modules array in their
+      // appropriate order.
+      if (array_diff($extra_modules, $modules)) {
+        // Order the modules by the order returned by module_list().
+        $modules = array_intersect(module_list(), array_merge($modules, $extra_modules));
+      }
+      foreach ($modules as $module) {
+        // Since $modules is a merged array, for any given module, we do not
+        // know whether it has any particular implementation, so we need a
+        // function_exists().
+        $function = $module . '_' . $hook;
+        if (function_exists($function)) {
+          $functions[$cid][] = $function;
+        }
+        foreach ($extra_types as $extra_type) {
+          $function = $module . '_' . $extra_type . '_alter';
+          if (function_exists($function)) {
+            $functions[$cid][] = $function;
+          }
+        }
+      }
+    }
+  }
+
+  foreach ($functions[$cid] as $function) {
+    $function($data, $context1, $context2);
+  }
+}
\ No newline at end of file