From 6872f646d735fd6aa1c87317ebeffbe3274c1e08 Mon Sep 17 00:00:00 2001
From: Jose Lorenzo Rodriguez <jose.zap@gmail.com>
Date: Tue, 3 Jul 2012 23:03:13 -0430
Subject: [PATCH] Initial imlpementation for transactions and nested
 transactions

---
 .../Model/Datasource/Database/Connection.php  | 63 ++++++++++++++++++-
 lib/Cake/Model/Datasource/Database/Driver.php | 25 ++++++++
 .../Datasource/Database/Driver/Mysql.php      | 18 +++---
 3 files changed, 96 insertions(+), 10 deletions(-)

diff --git a/lib/Cake/Model/Datasource/Database/Connection.php b/lib/Cake/Model/Datasource/Database/Connection.php
index 80134b1c4c3..f82efab4546 100644
--- a/lib/Cake/Model/Datasource/Database/Connection.php
+++ b/lib/Cake/Model/Datasource/Database/Connection.php
@@ -35,6 +35,21 @@ class Connection {
  **/
 	protected $_connected = false;
 
+/**
+ * Contains how many nested transactions have been started
+ *
+ * @var int
+ **/
+	protected $_transactionLevel = 0;
+
+/**
+ * Whether this connection can and should use savepoints for nested
+ * transactions
+ *
+ * @var boolean
+ **/
+	protected $_useSavePoints = false;
+
 /**
  * Constructor
  *
@@ -215,7 +230,14 @@ public function delete($table, $conditions = array(), $types = array()) {
  * @return void
  **/
 	public function begin() {
-
+		$this->connect();
+		if (!$this->_transactionLevel) {
+			$this->_driver->beginTransaction();
+		}
+		$this->_transactionLevel++;
+		if ($this->_transactionLevel > 1 && $this->useSavePoints()) {
+			$this->createSavePoint($this->_transactionLevel);
+		}
 	}
 
 /**
@@ -225,7 +247,7 @@ public function begin() {
  **/
 
 	public function commit() {
-
+		
 	}
 
 /**
@@ -237,6 +259,43 @@ public function rollback() {
 
 	}
 
+/**
+ * Returns whether this connection is using savepoints for nested transactions
+ * If a boolean is passed as argument it will enable/disable the usage of savepoints
+ * only if driver the allows it.
+ *
+ * If you are trying to enable this feature, make sure you check the return value of this
+ * function to verify it was enabled successfuly
+ *
+ * ## Example:
+ *
+ * `$connection->useSavePoints(true)` Returns true if drivers supports save points, false otherwise
+ * `$connection->useSavePoints(false)` Disables usage of savepoints and returns false
+ * `$connection->useSavePoints()` Returns current status
+ *
+ * @return boolean true if enabled, false otherwise
+ **/
+	public function useSavePoints($enable = null) {
+		if ($enable === null) {
+			return $this->_useSavePoints;
+		}
+		if ($enable === false) {
+			return $this->_useSavePoints = false;
+		}
+
+		return $this->_useSavePoints = $this->_driver->supportsSavePoints();
+	}
+
+/**
+ * Creates a new save point for nested transactions
+ *
+ * @return void
+ **/
+	public function createSavePoint($name) {
+		$this->connect();
+		$this->execute($this->_driver->savePointSQL($name));
+	}
+
 /**
  * Quotes value to be used safely in database query
  *
diff --git a/lib/Cake/Model/Datasource/Database/Driver.php b/lib/Cake/Model/Datasource/Database/Driver.php
index 6bd3fc66a7d..420fb5015e9 100644
--- a/lib/Cake/Model/Datasource/Database/Driver.php
+++ b/lib/Cake/Model/Datasource/Database/Driver.php
@@ -39,4 +39,29 @@ public abstract function enabled();
  **/
 	public abstract function prepare($sql);
 
+/**
+ * Starts a transaction
+ *
+ * @return boolean true on success, false otherwise
+ **/
+	public abstract function beginTransaction();
+
+/**
+ * Returns whether this driver supports save points for nested transactions
+ *
+ * @return boolean true if save points are supported, false otherwise
+ **/
+	public function supportsSavePoints() {
+		true;
+	}
+
+/**
+ * Returns whether this driver supports save points for nested transactions
+ *
+ * @return boolean true if save points are supported, false otherwise
+ **/
+	public function savePointSQL($name) {
+		return 'SAVEPOINT LEVEL ' . $name;
+	}
+
 }
diff --git a/lib/Cake/Model/Datasource/Database/Driver/Mysql.php b/lib/Cake/Model/Datasource/Database/Driver/Mysql.php
index 1bfd6c0a29a..baaae8c250c 100644
--- a/lib/Cake/Model/Datasource/Database/Driver/Mysql.php
+++ b/lib/Cake/Model/Datasource/Database/Driver/Mysql.php
@@ -24,14 +24,7 @@ class Mysql extends \Cake\Model\Datasource\Database\Driver {
 	);
 
 /**
- * PDO instance associated to this connection
- *
- * @var PDO
- **/
-	protected $_conenction;
-
-/**
- * Establishes a conenction to the databse server
+ * Establishes a connection to the databse server
  *
  * @param array $config configuretion to be used for creating connection
  * @return boolean true on success
@@ -91,4 +84,13 @@ public  function prepare($sql) {
 		return new Statement($statement, $this);
 	}
 
+/**
+ * Starts a transaction
+ *
+ * @return boolean true on success, false otherwise
+ **/
+	public function beginTransaction() {
+		return $this->_connection->beginTransaction();
+	}
+
 }