2 files changed, 44 insertions, 14 deletions

diff --git a/includes/database/database.inc b/includes/database/database.inc
index cae50fb87..26ce6fcf4 100644
--- a/includes/database/database.inc
+++ b/includes/database/database.inc
@@ -194,7 +194,7 @@ abstract class DatabaseConnection extends PDO {
 
   /**
    * The key representing this connection.
-   * 
+   *
    * The key is a unique string which identifies a database connection. A
    * connection can be a single server or a cluster of master and slaves (use
    * target to pick between master and slave).
@@ -303,13 +303,29 @@ abstract class DatabaseConnection extends PDO {
     // Call PDO::__construct and PDO::setAttribute.
     parent::__construct($dsn, $username, $password, $driver_options);
 
-    // Set a specific PDOStatement class if the driver requires that.
+    // Set a Statement class, unless the driver opted out.
     if (!empty($this->statementClass)) {
       $this->setAttribute(PDO::ATTR_STATEMENT_CLASS, array($this->statementClass, array($this)));
     }
   }
 
   /**
+   * Destroys this Connection object.
+   *
+   * PHP does not destruct an object if it is still referenced in other
+   * variables. In case of PDO database connection objects, PHP only closes the
+   * connection when the PDO object is destructed, so any references to this
+   * object may cause the number of maximum allowed connections to be exceeded.
+   */
+  public function destroy() {
+    // Destroy all references to this connection by setting them to NULL.
+    // The Statement class attribute only accepts a new value that presents a
+    // proper callable, so we reset it to PDOStatement.
+    $this->setAttribute(PDO::ATTR_STATEMENT_CLASS, array('PDOStatement', array()));
+    $this->schema = NULL;
+  }
+
+  /**
    * Returns the default query options for any given query.
    *
    * A given query can be customized with a number of option flags in an
@@ -1627,8 +1643,8 @@ abstract class Database {
    */
   final public static function removeConnection($key) {
     if (isset(self::$databaseInfo[$key])) {
+      self::closeConnection(NULL, $key);
       unset(self::$databaseInfo[$key]);
-      unset(self::$connections[$key]);
       return TRUE;
     }
     else {
@@ -1694,11 +1710,24 @@ abstract class Database {
     if (!isset($key)) {
       $key = self::$activeKey;
     }
-    // To close the connection, we need to unset the static variable.
+    // To close a connection, it needs to be set to NULL and removed from the
+    // static variable. In all cases, closeConnection() might be called for a
+    // connection that was not opened yet, in which case the key is not defined
+    // yet and we just ensure that the connection key is undefined.
     if (isset($target)) {
+      if (isset(self::$connections[$key][$target])) {
+        self::$connections[$key][$target]->destroy();
+        self::$connections[$key][$target] = NULL;
+      }
       unset(self::$connections[$key][$target]);
     }
     else {
+      if (isset(self::$connections[$key])) {
+        foreach (self::$connections[$key] as $target => $connection) {
+          self::$connections[$key][$target]->destroy();
+          self::$connections[$key][$target] = NULL;
+        }
+      }
       unset(self::$connections[$key]);
     }
   }
@@ -1852,8 +1881,8 @@ class DatabaseTransaction {
    */
   protected $name;
 
-  public function __construct(DatabaseConnection &$connection, $name = NULL) {
-    $this->connection = &$connection;
+  public function __construct(DatabaseConnection $connection, $name = NULL) {
+    $this->connection = $connection;
     // If there is no transaction depth, then no transaction has started. Name
     // the transaction 'drupal_transaction'.
     if (!$depth = $connection->transactionDepth()) {
diff --git a/includes/database/mysql/database.inc b/includes/database/mysql/database.inc
index 7ad019e58..00d81f473 100644
--- a/includes/database/mysql/database.inc
+++ b/includes/database/mysql/database.inc
@@ -13,11 +13,11 @@
 class DatabaseConnection_mysql extends DatabaseConnection {
 
   /**
-   * Flag to indicate if we have registered the nextID cleanup function.
+   * Flag to indicate if the cleanup function in __destruct() should run.
    *
    * @var boolean
    */
-  protected $shutdownRegistered = FALSE;
+  protected $needsCleanup = FALSE;
 
   public function __construct(array $connection_options = array()) {
     // This driver defaults to transaction support, except if explicitly passed FALSE.
@@ -78,6 +78,12 @@ class DatabaseConnection_mysql extends DatabaseConnection {
     $this->exec(implode('; ', $connection_options['init_commands']));
   }
 
+  public function __destruct() {
+    if ($this->needsCleanup) {
+      $this->nextIdDelete();
+    }
+  }
+
   public function queryRange($query, $from, $count, array $args = array(), array $options = array()) {
     return $this->query($query . ' LIMIT ' . (int) $from . ', ' . (int) $count, $args, $options);
   }
@@ -115,12 +121,7 @@ class DatabaseConnection_mysql extends DatabaseConnection {
       $this->query('INSERT INTO {sequences} (value) VALUES (:value) ON DUPLICATE KEY UPDATE value = value', array(':value' => $existing_id));
       $new_id = $this->query('INSERT INTO {sequences} () VALUES ()', array(), array('return' => Database::RETURN_INSERT_ID));
     }
-    if (!$this->shutdownRegistered) {
-      // Use register_shutdown_function() here to keep the database system
-      // independent of Drupal.
-      register_shutdown_function(array($this, 'nextIdDelete'));
-      $shutdownRegistered = TRUE;
-    }
+    $this->needsCleanup = TRUE;
     return $new_id;
   }