PetaPoco - add support for transaction level

src/Umbraco.Core/Persistence/PetaPoco.cs

@@ -215,6 +215,10 @@ namespace Umbraco.Core.Persistence
 				_paramPrefix = "?";
 			if (_dbType == DBType.Oracle)
 				_paramPrefix = ":";
+
+            // by default use MSSQL default ReadCommitted level
+            //TODO change to RepeatableRead - but that is breaking
+		    _isolationLevel = IsolationLevel.ReadCommitted;
 		}
 
 		// Automatically close one open shared connection
@@ -237,7 +241,27 @@ namespace Umbraco.Core.Persistence
 				_sharedConnection.ConnectionString = _connectionString;
                 _sharedConnection.OpenWithRetry();//Changed .Open() => .OpenWithRetry() extension method
 
-				_sharedConnection = OnConnectionOpened(_sharedConnection);
+                // ensure we have the proper isolation level, as levels can leak in pools
+                // read http://stackoverflow.com/questions/9851415/sql-server-isolation-level-leaks-across-pooled-connections
+                // and http://stackoverflow.com/questions/641120/what-exec-sp-reset-connection-shown-in-sql-profiler-means
+                //
+                // NPoco has that code in OpenSharedConnectionImp (commented out?)
+                //using (var cmd = _sharedConnection.CreateCommand())
+                //{
+                //    cmd.CommandText = GetSqlForTransactionLevel(_isolationLevel);
+                //    cmd.CommandTimeout = CommandTimeout;
+                //    cmd.ExecuteNonQuery();
+                //}
+                //
+                // although MSDN documentation for SQL CE clearly states that the above method
+                // should work, it fails & reports an error parsing the query on 'TRANSACTION',
+                // and Google is no help (others have faced the same issue... no solution). So,
+                // switching to another method that does work on all databases.
+                var tr = _sharedConnection.BeginTransaction(_isolationLevel);
+                tr.Commit();
+                tr.Dispose();
+
+                _sharedConnection = OnConnectionOpened(_sharedConnection);
 
 				if (KeepConnectionAlive)
 					_sharedConnectionDepth++;		// Make sure you call Dispose
@@ -269,10 +293,20 @@ namespace Umbraco.Core.Persistence
 		// Helper to create a transaction scope
 		public Transaction GetTransaction()
 		{
-			return new Transaction(this);
-		}
+            return GetTransaction(_isolationLevel);
+        }
 
-		// Use by derived repo generated by T4 templates
+        public Transaction GetTransaction(IsolationLevel isolationLevel)
+        {
+            return new Transaction(this, isolationLevel);
+        }
+
+        public IsolationLevel CurrentTransactionIsolationLevel
+        {
+            get { return _transaction == null ? IsolationLevel.Unspecified : _transaction.IsolationLevel; }
+        }
+
+        // Use by derived repo generated by T4 templates
 		public virtual void OnBeginTransaction() { }
 		public virtual void OnEndTransaction() { }
 
@@ -281,17 +315,23 @@ namespace Umbraco.Core.Persistence
 		// Use `using (var scope=db.Transaction) { scope.Complete(); }` to ensure correct semantics
 		public void BeginTransaction()
 		{
-			_transactionDepth++;
+            BeginTransaction(_isolationLevel);
+        }
+
+        public void BeginTransaction(IsolationLevel isolationLevel)
+        {
+            _transactionDepth++;
 
 			if (_transactionDepth == 1)
 			{
 				OpenSharedConnection();
-				_transaction = _sharedConnection.BeginTransaction();
+				_transaction = _sharedConnection.BeginTransaction(isolationLevel);
 				_transactionCancelled = false;
 				OnBeginTransaction();
 			}
-
-		}
+            else if (isolationLevel > _transaction.IsolationLevel)
+                throw new Exception("Already in a transaction with a lower isolation level.");
+        }
 
 		// Internal helper to cleanup transaction stuff
 		void CleanupTransaction()
@@ -324,7 +364,27 @@ namespace Umbraco.Core.Persistence
 				CleanupTransaction();
 		}
 
-		// Helper to handle named parameters from object properties
+        // in NPoco this is in DatabaseType
+        private static string GetSqlForTransactionLevel(IsolationLevel isolationLevel)
+        {
+            switch (isolationLevel)
+            {
+                case IsolationLevel.ReadCommitted:
+                    return "SET TRANSACTION ISOLATION LEVEL READ COMMITTED";
+                case IsolationLevel.ReadUncommitted:
+                    return "SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED";
+                case IsolationLevel.RepeatableRead:
+                    return "SET TRANSACTION ISOLATION LEVEL REPEATABLE READ";
+                case IsolationLevel.Serializable:
+                    return "SET TRANSACTION ISOLATION LEVEL SERIALIZABLE";
+                case IsolationLevel.Snapshot:
+                    return "SET TRANSACTION ISOLATION LEVEL SNAPSHOT";
+                default:
+                    return "SET TRANSACTION ISOLATION LEVEL READ COMMITTED";
+            }
+        }
+        
+        // Helper to handle named parameters from object properties
 		static Regex rxParams = new Regex(@"(?<!@)@\w+", RegexOptions.Compiled);
 		public static string ProcessParams(string _sql, object[] args_src, List<object> args_dest)
 		{
@@ -2264,16 +2324,17 @@ namespace Umbraco.Core.Persistence
 		string _lastSql;
 		object[] _lastArgs;
 		string _paramPrefix = "@";
+	    IsolationLevel _isolationLevel;
 	}
 
 	// Transaction object helps maintain transaction depth counts
 	public class Transaction : IDisposable
 	{
-		public Transaction(Database db)
-		{
-			_db = db;
-			_db.BeginTransaction();
-		}
+        public Transaction(Database db, IsolationLevel isolationLevel)
+        {
+            _db = db;
+            _db.BeginTransaction(isolationLevel);
+        }
 
 		public virtual void Complete()
 		{