Merge pull request #1497 from mysql-net/avoid-set-names

Avoid SET NAMES commands if not needed. For MariaDB >= 11.5, session variables are sent in the initial OK Packet, permitting MySqlConnector to avoid initial SET NAMES query, since charset is already known.

src/MySqlConnector/Core/IServerCapabilities.cs

@@ -0,0 +1,7 @@
+namespace MySqlConnector.Core;
+
+internal interface IServerCapabilities
+{
+	bool SupportsDeprecateEof { get; }
+	bool SupportsSessionTrack { get; }
+}

src/MySqlConnector/Core/ResultSet.cs

@@ -38,7 +38,7 @@ public async Task ReadResultSetHeaderAsync(IOBehavior ioBehavior)
 				var firstByte = payload.HeaderByte;
 				if (firstByte == OkPayload.Signature)
 				{
-					var ok = OkPayload.Create(payload.Span, Session.SupportsDeprecateEof, Session.SupportsSessionTrack);
+					var ok = OkPayload.Create(payload.Span, Session);
 
 					// if we've read a result set header then this is a SELECT statement, so we shouldn't overwrite RecordsAffected
 					// (which should be -1 for SELECT) unless the server reports a non-zero count
@@ -252,9 +252,9 @@ public async Task<bool> ReadAsync(IOBehavior ioBehavior, CancellationToken cance
 
 		if (payload.HeaderByte == EofPayload.Signature)
 		{
-			if (Session.SupportsDeprecateEof && OkPayload.IsOk(payload.Span, Session.SupportsDeprecateEof))
+			if (Session.SupportsDeprecateEof && OkPayload.IsOk(payload.Span, Session))
 			{
-				var ok = OkPayload.Create(payload.Span, Session.SupportsDeprecateEof, Session.SupportsSessionTrack);
+				var ok = OkPayload.Create(payload.Span, Session);
 				BufferState = (ok.ServerStatus & ServerStatus.MoreResultsExist) == 0 ? ResultSetState.NoMoreData : ResultSetState.HasMoreData;
 				return null;
 			}

src/MySqlConnector/Core/ServerSession.cs

@@ -23,7 +23,7 @@ namespace MySqlConnector.Core;
 
 #pragma warning disable CA1001 // Types that own disposable fields should be disposable
 
-internal sealed partial class ServerSession
+internal sealed partial class ServerSession : IServerCapabilities
 {
 	public ServerSession(ILogger logger)
 		: this(logger, null, 0, Interlocked.Increment(ref s_lastId))
@@ -320,7 +320,7 @@ public void FinishQuerying()
 			SendAsync(payload, IOBehavior.Synchronous, CancellationToken.None).GetAwaiter().GetResult();
 			payload = ReceiveReplyAsync(IOBehavior.Synchronous, CancellationToken.None).GetAwaiter().GetResult();
 #pragma warning restore CA2012
-			OkPayload.Verify(payload.Span, SupportsDeprecateEof, SupportsSessionTrack);
+			OkPayload.Verify(payload.Span, this);
 		}
 
 		lock (m_lock)
@@ -532,19 +532,30 @@ public async Task DisposeAsync(IOBehavior ioBehavior, CancellationToken cancella
 				payload = await SwitchAuthenticationAsync(cs, password, payload, ioBehavior, cancellationToken).ConfigureAwait(false);
 			}
 
-			var ok = OkPayload.Create(payload.Span, SupportsDeprecateEof, SupportsSessionTrack);
+			var ok = OkPayload.Create(payload.Span, this);
 			var statusInfo = ok.StatusInfo;
 
 			if (m_useCompression)
 				m_payloadHandler = new CompressedPayloadHandler(m_payloadHandler.ByteHandler);
 
-			// set 'collation_connection' to the server default
-			await SendAsync(m_setNamesPayload, ioBehavior, cancellationToken).ConfigureAwait(false);
-			payload = await ReceiveReplyAsync(ioBehavior, cancellationToken).ConfigureAwait(false);
-			OkPayload.Verify(payload.Span, SupportsDeprecateEof, SupportsSessionTrack);
+			// send 'SET NAMES' to set the character set and collation unless the server reports that it's already using the desired character set (e.g., MariaDB >= 11.5)
+			if (ok.NewCharacterSet != (ServerVersion.Version >= ServerVersions.SupportsUtf8Mb4 ? CharacterSet.Utf8Mb4Binary : CharacterSet.Utf8Mb3Binary))
+			{
+				// set 'collation_connection' to the server default
+				await SendAsync(m_setNamesPayload, ioBehavior, cancellationToken).ConfigureAwait(false);
+				payload = await ReceiveReplyAsync(ioBehavior, cancellationToken).ConfigureAwait(false);
+				OkPayload.Verify(payload.Span, this);
+			}
 
 			if (ShouldGetRealServerDetails(cs))
+			{
 				await GetRealServerDetailsAsync(ioBehavior, CancellationToken.None).ConfigureAwait(false);
+			}
+			else if (ok.NewConnectionId is int newConnectionId && newConnectionId != ConnectionId)
+			{
+				Log.ChangingConnectionId(m_logger, Id, ConnectionId, newConnectionId, ServerVersion.OriginalString, ServerVersion.OriginalString);
+				ConnectionId = newConnectionId;
+			}
 
 			m_payloadHandler.ByteHandler.RemainingTimeout = Constants.InfiniteTimeout;
 			return statusInfo;
@@ -584,18 +595,18 @@ public async Task<bool> TryResetConnectionAsync(ConnectionSettings cs, MySqlConn
 
 					// read two OK replies
 					payload = await ReceiveReplyAsync(1, ioBehavior, cancellationToken).ConfigureAwait(false);
-					OkPayload.Verify(payload.Span, SupportsDeprecateEof, SupportsSessionTrack);
+					OkPayload.Verify(payload.Span, this);
 
 					payload = await ReceiveReplyAsync(1, ioBehavior, cancellationToken).ConfigureAwait(false);
-					OkPayload.Verify(payload.Span, SupportsDeprecateEof, SupportsSessionTrack);
+					OkPayload.Verify(payload.Span, this);
 
 					return true;
 				}
 
 				Log.SendingResetConnectionRequest(m_logger, Id, ServerVersion.OriginalString);
 				await SendAsync(ResetConnectionPayload.Instance, ioBehavior, cancellationToken).ConfigureAwait(false);
 				payload = await ReceiveReplyAsync(ioBehavior, cancellationToken).ConfigureAwait(false);
-				OkPayload.Verify(payload.Span, SupportsDeprecateEof, SupportsSessionTrack);
+				OkPayload.Verify(payload.Span, this);
 			}
 			else
 			{
@@ -619,13 +630,13 @@ public async Task<bool> TryResetConnectionAsync(ConnectionSettings cs, MySqlConn
 					Log.OptimisticReauthenticationFailed(m_logger, Id);
 					payload = await SwitchAuthenticationAsync(cs, password, payload, ioBehavior, cancellationToken).ConfigureAwait(false);
 				}
-				OkPayload.Verify(payload.Span, SupportsDeprecateEof, SupportsSessionTrack);
+				OkPayload.Verify(payload.Span, this);
 			}
 
 			// set 'collation_connection' to the server default
 			await SendAsync(m_setNamesPayload, ioBehavior, cancellationToken).ConfigureAwait(false);
 			payload = await ReceiveReplyAsync(ioBehavior, cancellationToken).ConfigureAwait(false);
-			OkPayload.Verify(payload.Span, SupportsDeprecateEof, SupportsSessionTrack);
+			OkPayload.Verify(payload.Span, this);
 
 			return true;
 		}
@@ -684,7 +695,7 @@ private async Task<PayloadData> SwitchAuthenticationAsync(ConnectionSettings cs,
 				payload = await ReceiveReplyAsync(ioBehavior, cancellationToken).ConfigureAwait(false);
 
 				// OK payload can be sent immediately (e.g., if password is empty) bypassing even the fast authentication path
-				if (OkPayload.IsOk(payload.Span, SupportsDeprecateEof))
+				if (OkPayload.IsOk(payload.Span, this))
 					return payload;
 
 				var cachingSha2ServerResponsePayload = CachingSha2ServerResponsePayload.Create(payload.Span);
@@ -824,7 +835,7 @@ public async ValueTask<bool> TryPingAsync(bool logInfo, IOBehavior ioBehavior, C
 			Log.PingingServer(m_logger, Id);
 			await SendAsync(PingPayload.Instance, ioBehavior, cancellationToken).ConfigureAwait(false);
 			var payload = await ReceiveReplyAsync(ioBehavior, cancellationToken).ConfigureAwait(false);
-			OkPayload.Verify(payload.Span, SupportsDeprecateEof, SupportsSessionTrack);
+			OkPayload.Verify(payload.Span, this);
 			Log.SuccessfullyPingedServer(m_logger, logInfo ? LogLevel.Information : LogLevel.Trace, Id);
 			return true;
 		}
@@ -1662,8 +1673,8 @@ static void ReadRow(ReadOnlySpan<byte> span, out int? connectionId, out ServerVe
 
 			// OK/EOF payload
 			payload = await ReceiveReplyAsync(ioBehavior, CancellationToken.None).ConfigureAwait(false);
-			if (OkPayload.IsOk(payload.Span, SupportsDeprecateEof))
-				OkPayload.Verify(payload.Span, SupportsDeprecateEof, SupportsSessionTrack);
+			if (OkPayload.IsOk(payload.Span, this))
+				OkPayload.Verify(payload.Span, this);
 			else
 				EofPayload.Create(payload.Span);
 

src/MySqlConnector/MySqlConnection.cs

@@ -161,23 +161,23 @@ private async ValueTask<MySqlTransaction> BeginTransactionAsync(IsolationLevel i
 
 			// read the two OK replies
 			var payload = await m_session.ReceiveReplyAsync(1, ioBehavior, cancellationToken).ConfigureAwait(false);
-			OkPayload.Verify(payload.Span, m_session.SupportsDeprecateEof, m_session.SupportsSessionTrack);
+			OkPayload.Verify(payload.Span, m_session);
 
 			payload = await m_session.ReceiveReplyAsync(1, ioBehavior, cancellationToken).ConfigureAwait(false);
-			OkPayload.Verify(payload.Span, m_session.SupportsDeprecateEof, m_session.SupportsSessionTrack);
+			OkPayload.Verify(payload.Span, m_session);
 		}
 		else
 		{
 			// send the two packets separately
 			await m_session.SendAsync(new Protocol.PayloadData(startTransactionPayload.Slice(4, startTransactionPayload.Span[0])), ioBehavior, cancellationToken).ConfigureAwait(false);
 
 			var payload = await m_session.ReceiveReplyAsync(ioBehavior, cancellationToken).ConfigureAwait(false);
-			OkPayload.Verify(payload.Span, m_session.SupportsDeprecateEof, m_session.SupportsSessionTrack);
+			OkPayload.Verify(payload.Span, m_session);
 
 			await m_session.SendAsync(new Protocol.PayloadData(startTransactionPayload.Slice(8 + startTransactionPayload.Span[0], startTransactionPayload.Span[startTransactionPayload.Span[0] + 4])), ioBehavior, cancellationToken).ConfigureAwait(false);
 
 			payload = await m_session.ReceiveReplyAsync(ioBehavior, cancellationToken).ConfigureAwait(false);
-			OkPayload.Verify(payload.Span, m_session.SupportsDeprecateEof, m_session.SupportsSessionTrack);
+			OkPayload.Verify(payload.Span, m_session);
 		}
 
 		var transaction = new MySqlTransaction(this, isolationLevel, m_transactionLogger);
@@ -487,7 +487,9 @@ private async Task ChangeDatabaseAsync(IOBehavior ioBehavior, string databaseNam
 		using (var initDatabasePayload = InitDatabasePayload.Create(databaseName))
 			await m_session!.SendAsync(initDatabasePayload, ioBehavior, cancellationToken).ConfigureAwait(false);
 		var payload = await m_session.ReceiveReplyAsync(ioBehavior, cancellationToken).ConfigureAwait(false);
-		OkPayload.Verify(payload.Span, m_session.SupportsDeprecateEof, m_session.SupportsSessionTrack);
+		OkPayload.Verify(payload.Span, m_session);
+
+		// for non session tracking servers
 		m_session.DatabaseOverride = databaseName;
 	}
 
@@ -603,7 +605,7 @@ public async ValueTask ResetConnectionAsync(CancellationToken cancellationToken
 		Log.ResettingConnection(m_logger, session.Id);
 		await session.SendAsync(ResetConnectionPayload.Instance, AsyncIOBehavior, cancellationToken).ConfigureAwait(false);
 		var payload = await session.ReceiveReplyAsync(AsyncIOBehavior, cancellationToken).ConfigureAwait(false);
-		OkPayload.Verify(payload.Span, session.SupportsDeprecateEof, session.SupportsSessionTrack);
+		OkPayload.Verify(payload.Span, session);
 	}
 
 	[AllowNull]