Changed to simple transaction support. Updated documentation to point to MySQL transaction documentation.

Author: jflitton

Readme.md

@@ -703,49 +703,42 @@ connection.query(options, function(err, results) {
 
 ## Transactions
 
-Transactions are useful when combined with pooling in cases where
-multiple dependent nested queries occur:
+Simple transaction support is available at the connection level:
 
 ```js
-var title = 'Hello MySQL';
-
-pool.getConnection(function(err, connection) {
-  connection.beginTransaction(function(err) {
-    if (err) {
-      connection.release();
-      throw err;
+connection.beginTransaction(function(err) {
+  if (err) { throw err; }
+  connection.query('INSERT INTO posts SET title=?', title, function(err, result) {
+    if (err) { 
+      connection.rollback(function() {
+        throw err;
+      });
     }
-    connection.query('INSERT INTO posts SET title=?', title, function(err, result) {
-      if (err) {
-        connection.release();
-	    throw err;
-	  }
-
-	  var log = 'Post ' + result.insertId + ' added';
-
-	  connection.query('INSERT INTO log SET data=?', log, function(err, result) {
-	    if (err) {
-	      connection.release();
-	      throw err;
-	    }
-	    connection.commit(function(err) {
-	      if (err) {
-	        connection.release();
-	        throw err;
-	      }
-	      console.log('success!');
-	    });
+
+	var log = 'Post ' + result.insertId + ' added';
+
+	connection.query('INSERT INTO log SET data=?', log, function(err, result) {
+	  if (err) { 
+        connection.rollback(function() {
+          throw err;
+        });
+      }  
+	  connection.commit(function(err) {
+	    if (err) { 
+          connection.rollback(function() {
+            throw err;
+          });
+        }
+	    console.log('success!');
 	  });
-	});
+    });
   });
 });
 ```
-
-Note that all transactions must be explicitly committed.
-```connection.release()``` will roll back any open
-transactions on the connection before releasing it.
-
-```connection.rollback(function(err))``` can also be used to manually roll back queries.
+Please note that beginTransaction(), commit() and rollback() are simply convenience
+functions that execute the START TRANSACTION, COMMIT, and ROLLBACK commands respectively.
+It is important to understand that many commands in MySQL can cause an implicit commit,
+as described [in the MySQL documentation]: http://dev.mysql.com/doc/refman/5.5/en/implicit-commit.html
 
 ## Error handling
 

lib/Connection.js

@@ -17,7 +17,6 @@ function Connection(options) {
   this._protocol      = new Protocol({config: this.config, connection: this});
   this._connectCalled = false;
   this.state          = "disconnected";
-  this.inTransaction = false;
 }
 
 Connection.createQuery = function(sql, values, cb) {
@@ -95,60 +94,33 @@ Connection.prototype.changeUser = function(options, cb){
     database      : options.database || this.config.database,
     charsetNumber : charsetNumber,
     currentConfig : this.config
-  }, function(err) {
-    self.inTransaction = false;
-    return cb(err);
-  });
+  }, cb);
 };
 
 Connection.prototype.beginTransaction = function(cb) {
-  if (this.inTransaction) {
-    return cb(new Error('Cannot begin transaction: A transaction is already open.'));
-  }
-
   this._implyConnect();
-
-  var self = this;
-  var query = Connection.createQuery('BEGIN', function(err) {
-    self.inTransaction = true;
-    return cb(err);
-  });
-
+  
+  var query = Connection.createQuery('START TRANSACTION', cb);
   query._connection = this;
+  
   return this._protocol._enqueue(query);
 };
 
 Connection.prototype.commit = function(cb) {
-  if (!this.inTransaction) {
-    return cb(new Error('Cannot commit: No transaction is currently open.'));
-  }
-
   this._implyConnect();
-
-  var self = this;
-  var query = Connection.createQuery('COMMIT', function(err) {
-    self.inTransaction = false;
-    return cb(err);
-  });
-
+  
+  var query = Connection.createQuery('COMMIT', cb);
   query._connection = this;
+  
   return this._protocol._enqueue(query);
 };
 
 Connection.prototype.rollback = function(cb) {
-  if (!this.inTransaction) {
-    return cb(new Error('Cannot roll back: No transaction is currently open.'));
-  }
-
   this._implyConnect();
-
-  var self = this;
-  var query = Connection.createQuery('ROLLBACK', function(err) {
-    self.inTransaction = false;
-    return cb(err);
-  });
-
+  
+  var query = Connection.createQuery('ROLLBACK', cb);
   query._connection = this;
+  
   return this._protocol._enqueue(query);
 };
 

lib/Pool.js

@@ -69,11 +69,6 @@ Pool.prototype.getConnection = function (cb) {
 Pool.prototype.releaseConnection = function (connection) {
   var cb;
 
-  if (connection.inTransaction) {
-    // We're in a transaction.  Roll it back before releasing
-    return process.nextTick(connection.rollback.bind(connection, this.releaseConnection.bind(this, connection)));
-  }
-
   if (!connection._pool) {
     // The connection has been removed from the pool and is no longer good.
     if (this._connectionQueue.length) {

test/integration/connection/test-transaction-begin-already-open.js

@@ -15,8 +15,7 @@ connection.query([
 
 connection.beginTransaction(function (err) {
   assert.ifError(err);
-  assert.strictEqual(connection.inTransaction, true);
-
+  
   var row = {
     id: 1,
     title: 'Test row'
@@ -30,7 +29,6 @@ connection.beginTransaction(function (err) {
 
       connection.query('SELECT * FROM ' + table, function(err, rows) {
         assert.ifError(err);
-        assert.strictEqual(connection.inTransaction, false);
         connection.end();
         assert.equal(rows.length, 1);
       });

test/integration/connection/test-transaction-commit-not-open.js

@@ -15,8 +15,7 @@ connection.query([
 
 connection.beginTransaction(function (err) {
   assert.ifError(err);
-  assert.strictEqual(connection.inTransaction, true);
-
+  
   var row = {
     id: 1,
     title: 'Test row'
@@ -30,7 +29,6 @@ connection.beginTransaction(function (err) {
 
       connection.query('SELECT * FROM ' + table, function(err, rows) {
         assert.ifError(err);
-        assert.strictEqual(connection.inTransaction, false);
         connection.end();
         assert.equal(rows.length, 0);
       });