Eliminate temporary single-element IMySqlCommand array allocation.

Use CommandListPosition directly to store the potential list of commands. This optimizes the common case of executing a single MySqlCommand.

src/MySqlConnector/Core/CommandExecutor.cs

@@ -8,22 +8,22 @@ namespace MySqlConnector.Core;
 
 internal static class CommandExecutor
 {
-	public static async ValueTask<MySqlDataReader> ExecuteReaderAsync(IReadOnlyList<IMySqlCommand> commands, ICommandPayloadCreator payloadCreator, CommandBehavior behavior, Activity? activity, IOBehavior ioBehavior, CancellationToken cancellationToken)
+	public static async ValueTask<MySqlDataReader> ExecuteReaderAsync(CommandListPosition commandListPosition, ICommandPayloadCreator payloadCreator, CommandBehavior behavior, Activity? activity, IOBehavior ioBehavior, CancellationToken cancellationToken)
 	{
 		try
 		{
 			cancellationToken.ThrowIfCancellationRequested();
-			var commandListPosition = new CommandListPosition(commands);
-			var command = commands[0];
+			var command = commandListPosition.CommandAt(0);
 
 			// pre-requisite: Connection is non-null must be checked before calling this method
 			var connection = command.Connection!;
 
-			Log.CommandExecutorExecuteReader(command.Logger, connection.Session.Id, ioBehavior, commands.Count);
+			Log.CommandExecutorExecuteReader(command.Logger, connection.Session.Id, ioBehavior, commandListPosition.CommandCount);
 
 			Dictionary<string, CachedProcedure?>? cachedProcedures = null;
-			foreach (var command2 in commands)
+			for (var commandIndex = 0; commandIndex < commandListPosition.CommandCount; commandIndex++)
 			{
+				var command2 = commandListPosition.CommandAt(commandIndex);
 				if (command2.CommandType == CommandType.StoredProcedure)
 				{
 					cachedProcedures ??= new();

src/MySqlConnector/Core/CommandListPosition.cs

@@ -5,18 +5,37 @@ namespace MySqlConnector.Core;
 /// </summary>
 internal struct CommandListPosition
 {
-	public CommandListPosition(IReadOnlyList<IMySqlCommand> commands)
+	public CommandListPosition(object commands)
 	{
-		Commands = commands;
+		m_commands = commands;
+		CommandCount = commands switch
+		{
+			MySqlCommand _ => 1,
+			IReadOnlyList<MySqlBatchCommand> list => list.Count,
+			_ => 0,
+		};
 		PreparedStatements = null;
 		CommandIndex = 0;
 		PreparedStatementIndex = 0;
 	}
 
+	public readonly IMySqlCommand CommandAt(int index) =>
+		m_commands switch
+		{
+			MySqlCommand command when index is 0 => command,
+			IReadOnlyList<MySqlBatchCommand> list => list[index],
+			_ => throw new ArgumentOutOfRangeException(nameof(index)),
+		};
+
+	/// <summary>
+	/// The commands in this list; either a singular <see cref="MySqlCommand"/> or a <see cref="IReadOnlyList{MySqlBatchCommand}"/>.
+	/// </summary>
+	private readonly object m_commands;
+
 	/// <summary>
-	/// The commands in the list.
+	/// The number of commands in the list.
 	/// </summary>
-	public IReadOnlyList<IMySqlCommand> Commands { get; }
+	public readonly int CommandCount;
 
 	/// <summary>
 	/// Associated prepared statements of commands

src/MySqlConnector/Core/ConcatenatedCommandPayloadCreator.cs

@@ -10,14 +10,14 @@ internal sealed class ConcatenatedCommandPayloadCreator : ICommandPayloadCreator
 
 	public bool WriteQueryCommand(ref CommandListPosition commandListPosition, IDictionary<string, CachedProcedure?> cachedProcedures, ByteBufferWriter writer, bool appendSemicolon)
 	{
-		if (commandListPosition.CommandIndex == commandListPosition.Commands.Count)
+		if (commandListPosition.CommandIndex == commandListPosition.CommandCount)
 			return false;
 
 		writer.Write((byte) CommandKind.Query);
 
 		// ConcatenatedCommandPayloadCreator is only used by MySqlBatch, and MySqlBatchCommand doesn't expose attributes,
 		// so just write an empty attribute set if the server needs it.
-		if (commandListPosition.Commands[commandListPosition.CommandIndex].Connection!.Session.SupportsQueryAttributes)
+		if (commandListPosition.CommandAt(commandListPosition.CommandIndex).Connection!.Session.SupportsQueryAttributes)
 		{
 			// attribute count
 			writer.WriteLengthEncodedInteger(0);
@@ -29,15 +29,15 @@ public bool WriteQueryCommand(ref CommandListPosition commandListPosition, IDict
 		bool isComplete;
 		do
 		{
-			var command = commandListPosition.Commands[commandListPosition.CommandIndex];
+			var command = commandListPosition.CommandAt(commandListPosition.CommandIndex);
 			Log.PreparingCommandPayload(command.Logger, command.Connection!.Session.Id, command.CommandText!);
 
 			isComplete = SingleCommandPayloadCreator.WriteQueryPayload(command, cachedProcedures, writer,
-				commandListPosition.CommandIndex < commandListPosition.Commands.Count - 1 || appendSemicolon,
+				commandListPosition.CommandIndex < commandListPosition.CommandCount - 1 || appendSemicolon,
 				commandListPosition.CommandIndex == 0,
-				commandListPosition.CommandIndex == commandListPosition.Commands.Count - 1);
+				commandListPosition.CommandIndex == commandListPosition.CommandCount - 1);
 			commandListPosition.CommandIndex++;
-		} while (commandListPosition.CommandIndex < commandListPosition.Commands.Count && isComplete);
+		} while (commandListPosition.CommandIndex < commandListPosition.CommandCount && isComplete);
 
 		return true;
 	}

src/MySqlConnector/Core/SingleCommandPayloadCreator.cs

@@ -14,10 +14,10 @@ internal sealed class SingleCommandPayloadCreator : ICommandPayloadCreator
 
 	public bool WriteQueryCommand(ref CommandListPosition commandListPosition, IDictionary<string, CachedProcedure?> cachedProcedures, ByteBufferWriter writer, bool appendSemicolon)
 	{
-		if (commandListPosition.CommandIndex == commandListPosition.Commands.Count)
+		if (commandListPosition.CommandIndex == commandListPosition.CommandCount)
 			return false;
 
-		var command = commandListPosition.Commands[commandListPosition.CommandIndex];
+		var command = commandListPosition.CommandAt(commandListPosition.CommandIndex);
 		commandListPosition.PreparedStatements = command.TryGetPreparedStatements();
 		if (commandListPosition.PreparedStatements is null)
 		{

src/MySqlConnector/MySqlBatch.cs

@@ -162,7 +162,7 @@ private ValueTask<MySqlDataReader> ExecuteReaderAsync(CommandBehavior behavior,
 		var payloadCreator = Connection!.Session.SupportsComMulti ? BatchedCommandPayloadCreator.Instance :
 			IsPrepared ? SingleCommandPayloadCreator.Instance :
 			ConcatenatedCommandPayloadCreator.Instance;
-		return CommandExecutor.ExecuteReaderAsync(BatchCommands!.Commands, payloadCreator, behavior, default, ioBehavior, cancellationToken);
+		return CommandExecutor.ExecuteReaderAsync(new(BatchCommands!.Commands), payloadCreator, behavior, default, ioBehavior, cancellationToken);
 	}
 
 #if NET6_0_OR_GREATER

src/MySqlConnector/MySqlCommand.cs

@@ -359,7 +359,7 @@ internal ValueTask<MySqlDataReader> ExecuteReaderNoResetTimeoutAsync(CommandBeha
 		var activity = NoActivity ? null : Connection!.Session.StartActivity(ActivitySourceHelper.ExecuteActivityName,
 			ActivitySourceHelper.DatabaseStatementTagName, CommandText);
 		m_commandBehavior = behavior;
-		return CommandExecutor.ExecuteReaderAsync(new IMySqlCommand[] { this }, SingleCommandPayloadCreator.Instance, behavior, activity, ioBehavior, cancellationToken);
+		return CommandExecutor.ExecuteReaderAsync(new(this), SingleCommandPayloadCreator.Instance, behavior, activity, ioBehavior, cancellationToken);
 	}
 
 	public MySqlCommand Clone() => new(this);

src/MySqlConnector/MySqlDataReader.cs

@@ -68,9 +68,9 @@ internal async Task<bool> NextResultAsync(IOBehavior ioBehavior, CancellationTok
 
 				if (!m_hasMoreResults)
 				{
-					if (m_commandListPosition.CommandIndex < m_commandListPosition.Commands.Count)
+					if (m_commandListPosition.CommandIndex < m_commandListPosition.CommandCount)
 					{
-						Command = m_commandListPosition.Commands[m_commandListPosition.CommandIndex];
+						Command = m_commandListPosition.CommandAt(m_commandListPosition.CommandIndex);
 						using (Command.CancellableCommand.RegisterCancel(cancellationToken))
 						{
 							var writer = new ByteBufferWriter();
@@ -485,7 +485,7 @@ internal async Task InitAsync(CommandListPosition commandListPosition, ICommandP
 				await ReadOutParametersAsync(command, m_resultSet, ioBehavior, cancellationToken).ConfigureAwait(false);
 
 			// if the command list has multiple commands, keep reading until a result set is found
-			while (m_resultSet.State == ResultSetState.NoMoreData && commandListPosition.CommandIndex < commandListPosition.Commands.Count)
+			while (m_resultSet.State == ResultSetState.NoMoreData && commandListPosition.CommandIndex < commandListPosition.CommandCount)
 			{
 				await NextResultAsync(ioBehavior, cancellationToken).ConfigureAwait(false);
 			}