Use server default collation. Fixes #626

Author: bgrainger

src/MySqlConnector/Core/ServerSession.cs

@@ -314,6 +314,7 @@ public async Task ConnectAsync(ConnectionSettings cs, ILoadBalancer loadBalancer
 					m_supportsSessionTrack = (initialHandshake.ProtocolCapabilities & ProtocolCapabilities.SessionTrack) != 0;
 					var serverSupportsSsl = (initialHandshake.ProtocolCapabilities & ProtocolCapabilities.Ssl) != 0;
 					m_characterSet = ServerVersion.Version >= ServerVersions.SupportsUtf8Mb4 ? CharacterSet.Utf8Mb4GeneralCaseInsensitive : CharacterSet.Utf8GeneralCaseInsensitive;
+					m_setNamesPayload = ServerVersion.Version >= ServerVersions.SupportsUtf8Mb4 ? s_setNamesUtf8mb4Payload : s_setNamesUtf8Payload;
 
 					Log.Info("Session{0} made connection; ServerVersion={1}; ConnectionId={2}; Compression={3}; Attributes={4}; DeprecateEof={5}; Ssl={6}; SessionTrack={7}",
 						m_logArguments[0], ServerVersion.OriginalString, ConnectionId,
@@ -370,6 +371,11 @@ public async Task ConnectAsync(ConnectionSettings cs, ILoadBalancer loadBalancer
 				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.Create(payload.AsSpan(), SupportsDeprecateEof, SupportsSessionTrack);
+
 				if (ShouldGetRealServerDetails())
 					await GetRealServerDetailsAsync(ioBehavior, CancellationToken.None).ConfigureAwait(false);
 			}
@@ -394,16 +400,12 @@ public async Task<bool> TryResetConnectionAsync(ConnectionSettings cs, IOBehavio
 				// clear all prepared statements; resetting the connection will clear them on the server
 				ClearPreparedStatements();
 
+				PayloadData payload;
 				if (DatabaseOverride is null && (ServerVersion.Version.CompareTo(ServerVersions.SupportsResetConnection) >= 0 || ServerVersion.MariaDbVersion?.CompareTo(ServerVersions.MariaDbSupportsResetConnection) >= 0))
 				{
 					m_logArguments[1] = ServerVersion.OriginalString;
 					Log.Debug("Session{0} ServerVersion={1} supports reset connection; sending reset connection request", m_logArguments);
 					await SendAsync(ResetConnectionPayload.Instance, ioBehavior, cancellationToken).ConfigureAwait(false);
-					var payload = await ReceiveReplyAsync(ioBehavior, cancellationToken).ConfigureAwait(false);
-					OkPayload.Create(payload.AsSpan(), SupportsDeprecateEof, SupportsSessionTrack);
-
-					// the "reset connection" packet also resets the connection charset, so we need to change that back to our default
-					await SendAsync(s_setNamesUtf8mb4Payload, ioBehavior, cancellationToken).ConfigureAwait(false);
 					payload = await ReceiveReplyAsync(ioBehavior, cancellationToken).ConfigureAwait(false);
 					OkPayload.Create(payload.AsSpan(), SupportsDeprecateEof, SupportsSessionTrack);
 				}
@@ -424,7 +426,7 @@ public async Task<bool> TryResetConnectionAsync(ConnectionSettings cs, IOBehavio
 					var hashedPassword = AuthenticationUtility.CreateAuthenticationResponse(AuthPluginData, 0, cs.Password);
 					using (var changeUserPayload = ChangeUserPayload.Create(cs.UserID, hashedPassword, cs.Database, m_characterSet, m_supportsConnectionAttributes ? cs.ConnectionAttributes : null))
 						await SendAsync(changeUserPayload, ioBehavior, cancellationToken).ConfigureAwait(false);
-					var payload = await ReceiveReplyAsync(ioBehavior, cancellationToken).ConfigureAwait(false);
+					payload = await ReceiveReplyAsync(ioBehavior, cancellationToken).ConfigureAwait(false);
 					if (payload.HeaderByte == AuthenticationMethodSwitchRequestPayload.Signature)
 					{
 						Log.Debug("Session{0} optimistic reauthentication failed; logging in again", m_logArguments);
@@ -433,6 +435,11 @@ public async Task<bool> TryResetConnectionAsync(ConnectionSettings cs, IOBehavio
 					OkPayload.Create(payload.AsSpan(), SupportsDeprecateEof, SupportsSessionTrack);
 				}
 
+				// set 'collation_connection' to the server default
+				await SendAsync(m_setNamesPayload, ioBehavior, cancellationToken).ConfigureAwait(false);
+				payload = await ReceiveReplyAsync(ioBehavior, cancellationToken).ConfigureAwait(false);
+				OkPayload.Create(payload.AsSpan(), SupportsDeprecateEof, SupportsSessionTrack);
+
 				return true;
 			}
 			catch (IOException ex)
@@ -1393,7 +1400,8 @@ private enum State
 		static ReadOnlySpan<byte> BeginCertificateBytes => new byte[] { 45, 45, 45, 45, 45, 66, 69, 71, 73, 78, 32, 67, 69, 82, 84, 73, 70, 73, 67, 65, 84, 69, 45, 45, 45, 45, 45 }; // -----BEGIN CERTIFICATE-----
 		static int s_lastId;
 		static readonly IMySqlConnectorLogger Log = MySqlConnectorLogManager.CreateLogger(nameof(ServerSession));
-		static readonly PayloadData s_setNamesUtf8mb4Payload = QueryPayload.Create("SET NAMES utf8mb4 COLLATE utf8mb4_general_ci;");
+		static readonly PayloadData s_setNamesUtf8Payload = QueryPayload.Create("SET NAMES utf8;");
+		static readonly PayloadData s_setNamesUtf8mb4Payload = QueryPayload.Create("SET NAMES utf8mb4;");
 
 		readonly object m_lock;
 		readonly object[] m_logArguments;
@@ -1412,6 +1420,7 @@ private enum State
 		bool m_supportsDeprecateEof;
 		bool m_supportsSessionTrack;
 		CharacterSet m_characterSet;
+		PayloadData m_setNamesPayload;
 		Dictionary<string, PreparedStatements> m_preparedStatements;
 	}
 }

tests/MySqlConnector.Tests/FakeMySqlServerConnection.cs

@@ -65,7 +65,7 @@ public async Task RunAsync(TcpClient client, CancellationToken token)
 						case CommandKind.Query:
 							var query = Encoding.UTF8.GetString(bytes, 1, bytes.Length - 1);
 							Match match;
-							if (query == "SET NAMES utf8mb4 COLLATE utf8mb4_general_ci;")
+							if (query == "SET NAMES utf8mb4;")
 							{
 								await SendAsync(stream, 1, WriteOk);
 							}

tests/SideBySide/CharacterSetTests.cs

@@ -1,4 +1,6 @@
+using System.Linq;
 using Dapper;
+using MySql.Data.MySqlClient;
 #if !BASELINE
 using MySqlConnector.Protocol;
 using MySqlConnector.Protocol.Serialization;
@@ -31,6 +33,67 @@ public void MaxLength()
 		}
 #endif
 
+		[Theory]
+		[InlineData(false)]
+		[InlineData(true)]
+		public void IllegalMixOfCollations(bool reopenConnection)
+		{
+			var csb = AppConfig.CreateConnectionStringBuilder();
+			csb.AllowUserVariables = true;
+			using (var connection = new MySqlConnection(csb.ConnectionString))
+			{
+				connection.Open();
+				connection.Execute(@"
+DROP TABLE IF EXISTS mix_collations;
+CREATE TABLE mix_collations (
+  id int(11) NOT NULL AUTO_INCREMENT,
+  test_col varchar(10) DEFAULT NULL,
+  PRIMARY KEY (id),
+  KEY ix_test (test_col)
+);
+INSERT INTO mix_collations (test_col)
+VALUES ('a'), ('b'), ('c'), ('d'), ('e'), ('f'), ('g'), ('h'), ('i'), ('j');");
+
+				if (reopenConnection)
+				{
+					connection.Close();
+					connection.Open();
+				}
+
+				using (var reader = connection.ExecuteReader(@"
+				SET @param = 'B';
+				SELECT * FROM mix_collations a WHERE a.test_col = @param"))
+				{
+					Assert.True(reader.Read());
+				}
+			}
+		}
+
+		[Theory]
+		[InlineData(false)]
+		[InlineData(true)]
+		public void CollationConnection(bool reopenConnection)
+		{
+			var csb = AppConfig.CreateConnectionStringBuilder();
+#if BASELINE
+			csb.CharacterSet = "utf8mb4";
+#endif
+			using (var connection = new MySqlConnection(csb.ConnectionString))
+			{
+				connection.Open();
+
+				if (reopenConnection)
+				{
+					connection.Close();
+					connection.Open();
+				}
+
+				var collation = connection.Query<string>(@"select @@collation_connection;").Single();
+				var expected = connection.ServerVersion.StartsWith("8.0") ? "utf8mb4_0900_ai_ci" : "utf8mb4_general_ci";
+				Assert.Equal(expected, collation);
+			}
+		}
+
 		readonly DatabaseFixture m_database;
 	}
 }