From d20e4571215b379676bf95898232717b121ad95b Mon Sep 17 00:00:00 2001
From: Dries Buytaert <dries@buytaert.net>
Date: Mon, 19 Jan 2009 10:46:52 +0000
Subject: - Patch #201122 by c960657, Moshe Weitzman: never write anonymous
 sessions, unless something has been written to . This is an important
 performance improvements -- as long as you use modules that use  carefully.
 It might be good to report some analytics about this in the performance
 settings page so administrators can see if there is a 'broken' module.

---
 includes/session.inc | 78 ++++++++++++++++++++++++++++++++++++++++++++++++----
 1 file changed, 73 insertions(+), 5 deletions(-)

(limited to 'includes/session.inc')

diff --git a/includes/session.inc b/includes/session.inc
index aae3f29ff..aa06db4ca 100644
--- a/includes/session.inc
+++ b/includes/session.inc
@@ -124,11 +124,10 @@ function _sess_read($key) {
 function _sess_write($key, $value) {
   global $user;
 
-  // If saving of session data is disabled or if the client doesn't have a session,
-  // and one isn't being created ($value), do nothing. This keeps crawlers out of
-  // the session table. This reduces memory and server load, and gives more useful
-  // statistics. We can't eliminate anonymous session table rows without breaking
-  // the "Who's Online" block.
+  // If saving of session data is disabled, or if a new empty anonymous session
+  // has been started, do nothing. This keeps anonymous users, including
+  // crawlers, out of the session table, unless they actually have something
+  // stored in $_SESSION.
   if (!drupal_save_session() || ($user->uid == 0 && empty($_COOKIE[session_name()]) && empty($value))) {
     return TRUE;
   }
@@ -158,6 +157,72 @@ function _sess_write($key, $value) {
   return TRUE;
 }
 
+/**
+ * Propagate $_SESSION and set session cookie if not already set. This function
+ * should be called before writing to $_SESSION, usually via
+ * drupal_set_session().
+ *
+ * @param $start
+ *   If FALSE, the session is not actually started. This is only used by
+ *   drupal_session_is_started().
+ * @return
+ *   TRUE if session has already been started, or FALSE if it has not.
+ */
+function drupal_session_start($start = TRUE) {
+  static $started = FALSE;
+  if ($start && !$started) {
+    $started = TRUE;
+    session_start();
+  }
+  return $started;
+}
+
+/**
+ * Return whether a session has been started and the $_SESSION variable is
+ * available.
+ */
+function drupal_session_is_started() {
+  return drupal_session_start(FALSE);
+}
+
+/**
+ * Get a session variable.
+ *
+ * @param $name
+ *   The name of the variable to get. If not supplied, all variables are returned.
+ * @return
+ *   The value of the variable, or FALSE if the variable is not set.
+ */
+function drupal_get_session($name = NULL) {
+  if (is_null($name)) {
+    return $_SESSION;
+  }
+  elseif (isset($_SESSION[$name])) {
+    return $_SESSION[$name];
+  }
+  else {
+    return FALSE;
+  }
+}
+
+/**
+ * Set a session variable. The variable becomes accessible via $_SESSION[$name]
+ * in the current and later requests. If there is no active PHP session prior
+ * to the call, one is started automatically.
+ *
+ * Anonymous users generate less server load if their $_SESSION variable is
+ * empty, so unused entries should be unset using unset($_SESSION['foo']).
+ *
+ * @param $name
+ *   The name of the variable to set.
+ * @param $value
+ *   The value to set.
+ */
+function drupal_set_session($name, $value) {
+  drupal_session_start();
+  $_SESSION[$name] = $value;
+}
+
 /**
  * Called when an anonymous user becomes authenticated or vice-versa.
  */
@@ -211,6 +276,9 @@ function _sess_destroy_sid($sid) {
   db_delete('sessions')
     ->condition('sid', $sid)
     ->execute();
+  // Unset cookie.
+  extract(session_get_cookie_params());
+  setcookie(session_name(), '', time() - 3600, $path, $domain, $secure, $httponly);
 }
 
 /**
-- 
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