Merge pull request #245 from bgrainger/performance

Improve performance by reducing allocations. One benchmark scenario now allocates 1/10 as much, and runs almost 2x faster.

Author: bgrainger

src/MySqlConnector/ByteArrayReader.cs

@@ -2,7 +2,7 @@
 
 namespace MySql.Data
 {
-	internal sealed class ByteArrayReader
+	internal struct ByteArrayReader
 	{
 		public ByteArrayReader(byte[] buffer, int offset, int length)
 		{
@@ -118,6 +118,8 @@ public ulong ReadLengthEncodedInteger()
 			byte encodedLength = m_buffer[m_offset++];
 			switch (encodedLength)
 			{
+			case 0xFB:
+				throw new FormatException("Length-encoded integer cannot have 0xFB prefix byte.");
 			case 0xFC:
 				return ReadFixedLengthUInt32(2);
 			case 0xFD:
@@ -131,6 +133,17 @@ public ulong ReadLengthEncodedInteger()
 			}
 		}
 
+		public int ReadLengthEncodedIntegerOrNull()
+		{
+			if (m_buffer[m_offset] == 0xFB)
+			{
+				// "NULL is sent as 0xfb" (https://dev.mysql.com/doc/internals/en/com-query-response.html#packet-ProtocolText::ResultsetRow)
+				m_offset++;
+				return -1;
+			}
+			return checked((int) ReadLengthEncodedInteger());
+		}
+
 		public ArraySegment<byte> ReadLengthEncodedByteString()
 		{
 			var length = checked((int) ReadLengthEncodedInteger());

src/MySqlConnector/MySqlClient/CommandExecutors/TextCommandExecutor.cs

@@ -51,7 +51,7 @@ public virtual async Task<DbDataReader> ExecuteReaderAsync(string commandText, M
 			CommandBehavior behavior, IOBehavior ioBehavior, CancellationToken cancellationToken)
 		{
 			cancellationToken.ThrowIfCancellationRequested();
-			using (cancellationToken.Register(m_command.Cancel))
+			using (m_command.RegisterCancel(cancellationToken))
 			{
 				m_command.Connection.Session.StartQuerying(m_command);
 				m_command.LastInsertedId = -1;

src/MySqlConnector/MySqlClient/MySqlCommand.cs

@@ -114,30 +114,23 @@ protected override DbDataReader ExecuteDbDataReader(CommandBehavior behavior) =>
 		public override Task<int> ExecuteNonQueryAsync(CancellationToken cancellationToken) =>
 			ExecuteNonQueryAsync(Connection.AsyncIOBehavior, cancellationToken);
 
-		internal async Task<int> ExecuteNonQueryAsync(IOBehavior ioBehavior, CancellationToken cancellationToken)
-		{
-			VerifyValid();
-			return await m_commandExecutor.ExecuteNonQueryAsync(CommandText, m_parameterCollection, ioBehavior, cancellationToken).ConfigureAwait(false);
-		}
+		internal Task<int> ExecuteNonQueryAsync(IOBehavior ioBehavior, CancellationToken cancellationToken) =>
+			!IsValid(out var exception) ? Utility.TaskFromException<int>(exception) :
+				m_commandExecutor.ExecuteNonQueryAsync(CommandText, m_parameterCollection, ioBehavior, cancellationToken);
 
 		public override Task<object> ExecuteScalarAsync(CancellationToken cancellationToken) =>
 			ExecuteScalarAsync(Connection.AsyncIOBehavior, cancellationToken);
 
-		internal async Task<object> ExecuteScalarAsync(IOBehavior ioBehavior, CancellationToken cancellationToken)
-		{
-			VerifyValid();
-			return await m_commandExecutor.ExecuteScalarAsync(CommandText, m_parameterCollection, ioBehavior, cancellationToken).ConfigureAwait(false);
-		}
+		internal Task<object> ExecuteScalarAsync(IOBehavior ioBehavior, CancellationToken cancellationToken) =>
+			!IsValid(out var exception) ? Utility.TaskFromException<object>(exception) :
+				m_commandExecutor.ExecuteScalarAsync(CommandText, m_parameterCollection, ioBehavior, cancellationToken);
 
 		protected override Task<DbDataReader> ExecuteDbDataReaderAsync(CommandBehavior behavior, CancellationToken cancellationToken) =>
 			ExecuteReaderAsync(behavior, Connection.AsyncIOBehavior, cancellationToken);
 
-		internal async Task<DbDataReader> ExecuteReaderAsync(CommandBehavior behavior, IOBehavior ioBehavior,
-			CancellationToken cancellationToken)
-		{
-			VerifyValid();
-			return await m_commandExecutor.ExecuteReaderAsync(CommandText, m_parameterCollection, behavior, ioBehavior, cancellationToken).ConfigureAwait(false);
-		}
+		internal Task<DbDataReader> ExecuteReaderAsync(CommandBehavior behavior, IOBehavior ioBehavior, CancellationToken cancellationToken) =>
+			!IsValid(out var exception) ? Utility.TaskFromException<DbDataReader>(exception) :
+				m_commandExecutor.ExecuteReaderAsync(CommandText, m_parameterCollection, behavior, ioBehavior, cancellationToken);
 
 		protected override void Dispose(bool disposing)
 		{
@@ -156,6 +149,23 @@ protected override void Dispose(bool disposing)
 
 		internal new MySqlConnection Connection => (MySqlConnection) DbConnection;
 
+		/// <summary>
+		/// Registers <see cref="Cancel"/> as a callback with <paramref name="token"/> if cancellation is supported.
+		/// </summary>
+		/// <param name="token">The <see cref="CancellationToken"/>.</param>
+		/// <returns>An object that must be disposed to revoke the cancellation registration.</returns>
+		/// <remarks>This method is more efficient than calling <code>token.Register(Command.Cancel)</code> because it avoids
+		/// unnecessary allocations.</remarks>
+		internal IDisposable RegisterCancel(CancellationToken token)
+		{
+			if (!token.CanBeCanceled)
+				return null;
+
+			if (m_cancelAction == null)
+				m_cancelAction = Cancel;
+			return token.Register(m_cancelAction);
+		}
+
 		private void VerifyNotDisposed()
 		{
 			if (m_parameterCollection == null)
@@ -164,21 +174,32 @@ private void VerifyNotDisposed()
 
 		private void VerifyValid()
 		{
-			VerifyNotDisposed();
-			if (DbConnection == null)
-				throw new InvalidOperationException("Connection property must be non-null.");
-			if (DbConnection.State != ConnectionState.Open && DbConnection.State != ConnectionState.Connecting)
-				throw new InvalidOperationException("Connection must be Open; current state is {0}".FormatInvariant(DbConnection.State));
-			if (DbTransaction != Connection.CurrentTransaction)
-				throw new InvalidOperationException("The transaction associated with this command is not the connection's active transaction.");
-			if (string.IsNullOrWhiteSpace(CommandText))
-				throw new InvalidOperationException("CommandText must be specified");
+			Exception exception;
+			if (!IsValid(out exception))
+				throw exception;
+		}
+
+		private bool IsValid(out Exception exception)
+		{
+			exception = null;
+			if (m_parameterCollection == null)
+				exception = new ObjectDisposedException(GetType().Name);
+			else if (DbConnection == null)
+				exception = new InvalidOperationException("Connection property must be non-null.");
+			else if (DbConnection.State != ConnectionState.Open && DbConnection.State != ConnectionState.Connecting)
+				exception = new InvalidOperationException("Connection must be Open; current state is {0}".FormatInvariant(DbConnection.State));
+			else if (DbTransaction != Connection.CurrentTransaction)
+				exception = new InvalidOperationException("The transaction associated with this command is not the connection's active transaction.");
+			else if (string.IsNullOrWhiteSpace(CommandText))
+				exception = new InvalidOperationException("CommandText must be specified");
+			return exception == null;
 		}
 
 		internal void ReaderClosed() => (m_commandExecutor as StoredProcedureCommandExecutor)?.SetParams();
 
 		MySqlParameterCollection m_parameterCollection;
 		CommandType m_commandType;
 		ICommandExecutor m_commandExecutor;
+		Action m_cancelAction;
 	}
 }

src/MySqlConnector/MySqlClient/MySqlDataReader.cs

@@ -108,7 +108,7 @@ private ValueTask<ResultSet> ScanResultSetAsync(IOBehavior ioBehavior, ResultSet
 
 		private async Task<ResultSet> ScanResultSetAsyncAwaited(IOBehavior ioBehavior, ResultSet resultSet, CancellationToken cancellationToken)
 		{
-			using (cancellationToken.Register(Command.Cancel))
+			using (Command.RegisterCancel(cancellationToken))
 			{
 				try
 				{

src/MySqlConnector/MySqlClient/MySqlStatementPreparer.cs

@@ -17,7 +17,7 @@ public MySqlStatementPreparer(string commandText, MySqlParameterCollection param
 
 		public ArraySegment<byte> ParseAndBindParameters()
 		{
-			using (var stream = new MemoryStream(m_commandText.Length))
+			using (var stream = new MemoryStream(m_commandText.Length + 1))
 			using (var writer = new BinaryWriter(stream, Encoding.UTF8))
 			{
 				writer.Write((byte) CommandKind.Query);

src/MySqlConnector/MySqlClient/Results/ResultSet.cs

@@ -162,7 +162,7 @@ private ValueTask<Row> ScanRowAsync(IOBehavior ioBehavior, Row row, Cancellation
 			if (BufferState == ResultSetState.HasMoreData || BufferState == ResultSetState.NoMoreData || BufferState == ResultSetState.None)
 				return new ValueTask<Row>((Row)null);
 
-			using (cancellationToken.Register(Command.Cancel))
+			using (Command.RegisterCancel(cancellationToken))
 			{
 				var payloadValueTask = Session.ReceiveReplyAsync(ioBehavior, CancellationToken.None);
 				return payloadValueTask.IsCompletedSuccessfully
@@ -197,7 +197,7 @@ Row ScanRowAsyncRemainder(PayloadData payload)
 				var reader = new ByteArrayReader(payload.ArraySegment);
 				for (var column = 0; column < m_dataOffsets.Length; column++)
 				{
-					var length = checked((int) ReadFieldLength(reader));
+					var length = reader.ReadLengthEncodedIntegerOrNull();
 					m_dataLengths[column] = length == -1 ? 0 : length;
 					m_dataOffsets[column] = length == -1 ? -1 : reader.Offset;
 					reader.Offset += m_dataLengths[column];
@@ -211,24 +211,6 @@ Row ScanRowAsyncRemainder(PayloadData payload)
 			}
 		}
 
-		private static long ReadFieldLength(ByteArrayReader reader)
-		{
-			var leadByte = reader.ReadByte();
-			switch (leadByte)
-			{
-				case 0xFB:
-					return -1;
-				case 0xFC:
-					return reader.ReadFixedLengthUInt32(2);
-				case 0xFD:
-					return reader.ReadFixedLengthUInt32(3);
-				case 0xFE:
-					return checked((long) reader.ReadFixedLengthUInt64(8));
-				default:
-					return leadByte;
-			}
-		}
-
 		public string GetName(int ordinal)
 		{
 			if (ColumnDefinitions == null)

src/MySqlConnector/Protocol/Serialization/CompressedPayloadHandler.cs

@@ -31,7 +31,7 @@ public IByteHandler ByteHandler
 		}
 
 		public ValueTask<ArraySegment<byte>> ReadPayloadAsync(ProtocolErrorBehavior protocolErrorBehavior, IOBehavior ioBehavior) =>
-			ProtocolUtility.ReadPayloadAsync(m_bufferedByteReader, new CompressedByteHandler(this, protocolErrorBehavior), () => default(int?), default(ArraySegment<byte>), protocolErrorBehavior, ioBehavior);
+			ProtocolUtility.ReadPayloadAsync(m_bufferedByteReader, new CompressedByteHandler(this, protocolErrorBehavior), () => -1, default(ArraySegment<byte>), protocolErrorBehavior, ioBehavior);
 
 		public ValueTask<int> WritePayloadAsync(ArraySegment<byte> payload, IOBehavior ioBehavior)
 		{