ClickHouse · scanhex12 · Jul 24, 2025 · Jul 24, 2025
diff --git a/ci/defs/defs.py b/ci/defs/defs.py
@@ -256,6 +256,12 @@ class CIFiles:
         platforms=Docker.Platforms.arm_amd,
         depends_on=[],
     ),
+    Docker.Config(
+        name="clickhouse/mysql-dotnet-client",
+        path="./docker/test/integration/mysql_dotnet_client",
+        platforms=Docker.Platforms.arm_amd,
+        depends_on=[],
+    ),
 ]
 
 

diff --git a/ci/docker/integration/mysql_dotnet_client/Dockerfile b/ci/docker/integration/mysql_dotnet_client/Dockerfile
@@ -0,0 +1,12 @@
+FROM ubuntu:18.04
+
+RUN apt-get update \
+    && apt-get install -y software-properties-common build-essential dotnet-sdk-8.0 curl
+
+ARG ver=42.2.12
+COPY Program.cs Program.cs
+COPY testapp.csproj testapp.csproj
+RUN dotnet add package MySql.Data
+RUN dotnet add package CommandLineParser    
+
+WORKDIR /testapp
diff --git a/ci/docker/integration/mysql_dotnet_client/Program.cs b/ci/docker/integration/mysql_dotnet_client/Program.cs
@@ -0,0 +1,90 @@
+using System;
+using MySql.Data.MySqlClient;
+
+class Program
+{
+    [Option('h', "host", HelpText = "Host of ClickHouse server")]
+    public string Host { get; set; }
+
+    [Option('p', "port", HelpText = "Port of ClickHouse server")]
+    public string Port { get; set; }
+
+    [Option('u', "username", HelpText = "Username")]
+    public string Username { get; set; }
+
+    [Option('p', "password", HelpText = "Password")]
+    public string Password { get; set; }
+    static void Main()
+    {
+        var parsed = Parser.Default.ParseArguments<Program>(args);
+        var options = parsed.Value;
+        var connectionString = $"Host={options.Host};Port={options.Port};Username={options.Username};Password={options.Password};Database=default;";
+
+        try
+        {
+            using (var connection = new MySqlConnection(connectionString))
+            {
+                Console.WriteLine("Openning connection...");
+                connection.Open();
+                Console.WriteLine("Connection openned!");
+
+                using (var cmd = new MySqlCommand("SELECT 1 as a;", connection))
+                using (var reader = cmd.ExecuteReader())
+                {
+                    while (reader.Read())
+                    {
+                        Console.WriteLine(reader.GetValue(0));
+                    }
+                }
+
+                string createTableSql = @"
+                    CREATE TABLE IF NOT EXISTS test_table (
+                        id UInt32,
+                        name String
+                    ) ENGINE = Memory";
+
+                using (var cmd = new MySqlCommand(createTableSql, connection))
+                {
+                    cmd.ExecuteNonQuery();
+                    Console.WriteLine("Table created or exists");
+                }
+
+                string insertSql = "INSERT INTO test_table (id, name) VALUES (1, 'Alice'), (2, 'Bob')";
+
+                using (var cmd = new MySqlCommand(insertSql, connection))
+                {
+                    int rows = cmd.ExecuteNonQuery();
+                    Console.WriteLine($"{rows} rows inserted");
+                }
+
+                string selectSql = "SELECT id, name FROM test_table";
+
+                using (var cmd = new MySqlCommand(selectSql, connection))
+                using (var reader = cmd.ExecuteReader())
+                {
+                    while (reader.Read())
+                    {
+                        uint id = (uint)reader.GetInt32(0);
+                        string name = reader.GetString(1);
+                        Console.WriteLine($"id={id}, name={name}");
+                    }
+                }
+            }
+        }
+        catch (Exception ex)
+        {
+            Console.WriteLine("=== Exception ===");
+            Console.WriteLine($"Type: {ex.GetType()}");
+            Console.WriteLine($"Message: {ex.Message}");
+            Console.WriteLine($"StackTrace: {ex.StackTrace}");
+
+            if (ex.InnerException != null)
+            {
+                Console.WriteLine("--- Inner Exception ---");
+                Console.WriteLine($"Type: {ex.InnerException.GetType()}");
+                Console.WriteLine($"Message: {ex.InnerException.Message}");
+                Console.WriteLine($"StackTrace: {ex.InnerException.StackTrace}");
+            }
+        }
+    }
+}
diff --git a/ci/docker/integration/mysql_dotnet_client/testapp.csproj b/ci/docker/integration/mysql_dotnet_client/testapp.csproj
@@ -0,0 +1,15 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net8.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="CommandLineParser" Version="2.9.1" />
+    <PackageReference Include="MySql.Data" Version="9.4.0" />
+  </ItemGroup>
+
+</Project>
diff --git a/ci/docker/integration/runner/dockerd-entrypoint.sh b/ci/docker/integration/runner/dockerd-entrypoint.sh
@@ -74,6 +74,7 @@ export DOCKER_MYSQL_JS_CLIENT_TAG=${DOCKER_MYSQL_JS_CLIENT_TAG:=latest}
 export DOCKER_MYSQL_PHP_CLIENT_TAG=${DOCKER_MYSQL_PHP_CLIENT_TAG:=latest}
 export DOCKER_NGINX_DAV_TAG=${DOCKER_NGINX_DAV_TAG:=latest}
 export DOCKER_POSTGRESQL_JAVA_CLIENT_TAG=${DOCKER_POSTGRESQL_JAVA_CLIENT_TAG:=latest}
+export DOCKER_MYSQL_DOTNET_CLIENT_TAG=${DOCKER_MYSQL_DOTNET_CLIENT_TAG:=latest}
 
 cd /ClickHouse/tests/integration
 exec "$@"
diff --git a/src/Server/MySQLHandler.cpp b/src/Server/MySQLHandler.cpp
@@ -29,6 +29,7 @@
 #include <Common/logger_useful.h>
 #include <Common/re2.h>
 #include <Common/setThreadName.h>
+#include "IO/WriteBufferFromString.h"
 
 #if USE_SSL
 #    include <Poco/Net/SSLManager.h>
@@ -169,6 +170,12 @@ static String killConnectionIdReplacementQuery(const String & query)
     return query;
 }
 
+/// Replace "SHOW COLLATIONS" into creating temporary system mysql table.
+static String showCollationsReplacementQuery(const String & /*query*/)
+{
+    return "SELECT * FROM emulated_collations";
+}
+
 
 /** MySQL returns this error code, HY000, so should we.
   *
@@ -218,11 +225,59 @@ MySQLHandler::MySQLHandler(
     queries_replacements.emplace("KILL QUERY", killConnectionIdReplacementQuery);
     queries_replacements.emplace("SHOW TABLE STATUS LIKE", showTableStatusReplacementQuery);
     queries_replacements.emplace("SHOW VARIABLES", selectEmptyReplacementQuery);
+    queries_replacements.emplace("SHOW COLLATION", showCollationsReplacementQuery);
     settings_replacements.emplace("SQL_SELECT_LIMIT", "limit");
     settings_replacements.emplace("NET_WRITE_TIMEOUT", "send_timeout");
     settings_replacements.emplace("NET_READ_TIMEOUT", "receive_timeout");
 }
 
+void MySQLHandler::setupSystemTables()
+{
+    auto execute_clickhouse_query = [&] (const String & query)
+    {
+        auto query_context = session->makeQueryContext();
+        query_context->setCurrentQueryId(fmt::format("mysql:{}:{}", connection_id, toString(UUIDHelpers::generateV4())));
+        CurrentThread::QueryScope query_scope{query_context};
+
+        auto buf = ReadBufferFromString(query);
+
+        String output;
+        auto out_buf = WriteBufferFromString(output);
+        executeQuery(buf, out_buf, false, query_context, {}, QueryFlags{}, {});
+    };
+
+    {
+        String create_query = R"(
+    CREATE TEMPORARY TABLE emulated_collations
+    (
+        Collation String,
+        Charset String,
+        Id UInt64,
+        Default String,
+        Compiled String,
+        Sortlen UInt32,
+        Pad_attribute Enum('PAD SPACE' = 1, 'NO PAD' = 2)
+    ) ENGINE = Memory;
+    )";
+
+        execute_clickhouse_query(create_query);
+    }
+
+    {
+        String insert_query = R"(
+    INSERT INTO emulated_collations VALUES
+    ('armscii8_bin',        'armscii8', 64, 'No',  'Yes', 1, 'PAD SPACE'),
+    ('armscii8_general_ci', 'armscii8', 32, 'Yes', 'Yes', 1, 'PAD SPACE'),
+    ('ascii_bin',           'ascii',    65, 'No',  'Yes', 1, 'PAD SPACE'),
+    ('ascii_general_ci',    'ascii',    11, 'Yes', 'Yes', 1, 'PAD SPACE'),
+    ('big5_bin',            'big5',     84, 'No',  'Yes', 1, 'PAD SPACE'),
+    ('big5_chinese_ci',     'big5',      1, 'Yes', 'Yes', 1, 'PAD SPACE'),
+    ('binary',              'binary',   63, 'Yes', 'Yes', 1, 'NO PAD');
+    )";
+        execute_clickhouse_query(insert_query);
+    }
+}
+
 MySQLHandler::~MySQLHandler() = default;
 
 void MySQLHandler::run()
@@ -286,6 +341,8 @@ void MySQLHandler::run()
         OKPacket ok_packet(0, handshake_response.capability_flags, 0, 0, 0);
         packet_endpoint->sendPacket(ok_packet);
 
+        setupSystemTables();
+
         while (tcp_server.isOpen())
         {
             packet_endpoint->resetSequenceId();
@@ -305,6 +362,7 @@ void MySQLHandler::run()
 
             if (!tcp_server.isOpen())
                 return;
+
             try
             {
                 switch (command)

diff --git a/src/Server/MySQLHandler.h b/src/Server/MySQLHandler.h
@@ -115,6 +115,9 @@ class MySQLHandler : public Poco::Net::TCPServerConnection
 
     ProfileEvents::Event read_event;
     ProfileEvents::Event write_event;
+
+    void setupSystemTables();
+    bool initialized_system_tables = false;
 };
 
 #if USE_SSL

diff --git a/tests/ci/integration_test_images.py b/tests/ci/integration_test_images.py
@@ -15,6 +15,7 @@
     "clickhouse/python-bottle": "DOCKER_PYTHON_BOTTLE_TAG",
     "clickhouse/integration-test-with-unity-catalog": "DOCKER_BASE_WITH_UNITY_CATALOG_TAG",
     "clickhouse/integration-test-with-hms": "DOCKER_BASE_WITH_HMS_TAG",
+    "clickhouse/mysql-dotnet-client": "DOCKER_MYSQL_DOTNET_CLIENT_TAG",
 }
 
 IMAGES = list(IMAGES_ENV.keys())

diff --git a/tests/integration/compose/docker_compose_mysql_dotnet_client.yml b/tests/integration/compose/docker_compose_mysql_dotnet_client.yml
@@ -0,0 +1,5 @@
+services:
+  dotnet:
+    image: clickhouse/mysql-dotnet-client:${mysql:-latest}
+    # to keep container running
+    command: sleep infinity
diff --git a/tests/integration/helpers/cluster.py b/tests/integration/helpers/cluster.py
@@ -519,6 +519,7 @@ def __init__(
         self.with_postgres = False
         self.with_postgres_cluster = False
         self.with_postgresql_java_client = False
+        self.with_mysql_dotnet_client = False
         self.with_kafka = False
         self.with_kafka_sasl = False
         self.with_kerberized_kafka = False
@@ -1235,6 +1236,25 @@ def setup_postgresql_java_client_cmd(
             p.join(docker_compose_yml_dir, "docker_compose_postgresql_java_client.yml"),
         )
 
+    def setup_mysql_dotnet_client_cmd(
+        self, instance, env_variables, docker_compose_yml_dir
+    ):
+        self.with_mysql_dotnet_client = True
+        self.base_cmd.extend(
+            [
+                "--file",
+                p.join(
+                    docker_compose_yml_dir, "docker_compose_mysql_dotnet_client.yml"
+                ),
+            ]
+        )
+        self.base_mysql_dotnet_client_cmd = self.compose_cmd(
+            "--env-file",
+            instance.env_file,
+            "--file",
+            p.join(docker_compose_yml_dir, "docker_compose_mysql_dotnet_client.yml"),
+        )
+
     def setup_kafka_cmd(self, instance, env_variables, docker_compose_yml_dir):
         self.with_kafka = True
         env_variables["KAFKA_HOST"] = self.kafka_host
@@ -1636,6 +1656,7 @@ def add_instance(
         with_postgres=False,
         with_postgres_cluster=False,
         with_postgresql_java_client=False,
+        with_mysql_dotnet_client=False,
         clickhouse_log_file=CLICKHOUSE_LOG_FILE,
         clickhouse_error_log_file=CLICKHOUSE_ERROR_LOG_FILE,
         with_mongo=False,
@@ -1800,6 +1821,7 @@ def add_instance(
             with_postgres=with_postgres,
             with_postgres_cluster=with_postgres_cluster,
             with_postgresql_java_client=with_postgresql_java_client,
+            with_mysql_dotnet_client=with_mysql_dotnet_client,
             clickhouse_start_command=clickhouse_start_command,
             clickhouse_start_extra_args=extra_args,
             main_config_name=main_config_name,
@@ -1901,6 +1923,13 @@ def add_instance(
                     instance, env_variables, docker_compose_yml_dir
                 )
             )
+
+        if with_mysql_dotnet_client and not self.with_mysql_dotnet_client:
+            cmds.append(
+                self.setup_mysql_dotnet_client_cmd(
+                    instance, env_variables, docker_compose_yml_dir
+                )
+            )
 
         if with_odbc_drivers and not self.with_odbc_drivers:
             self.with_odbc_drivers = True
@@ -3131,6 +3160,17 @@ def get_feature_flag_value(feature_flag):
                 self.up_called = True
                 self.wait_postgresql_java_client()
 
+            if (
+                self.with_mysql_dotnet_client
+                and self.base_mysql_dotnet_client_cmd
+            ):
+                logging.debug("Setup MySQL C# Client")
+                subprocess_check_call(
+                    self.base_mysql_dotnet_client_cmd + common_opts
+                )
+                self.up_called = True
+                self.wait_mysql_dotnet_client()
+
             if self.with_kafka and self.base_kafka_cmd:
                 logging.debug("Setup Kafka")
                 os.mkdir(self.kafka_dir)
@@ -3690,6 +3730,7 @@ def __init__(
         with_postgres,
         with_postgres_cluster,
         with_postgresql_java_client,
+        with_mysql_java_client,
         clickhouse_start_command=CLICKHOUSE_START_COMMAND,
         clickhouse_start_extra_args="",
         main_config_name="config.xml",
@@ -3764,6 +3805,7 @@ def __init__(
         self.with_postgres = with_postgres
         self.with_postgres_cluster = with_postgres_cluster
         self.with_postgresql_java_client = with_postgresql_java_client
+        self.with_mysql_dotnet_client = with_mysql_dotnet_client
         self.with_kafka = with_kafka
         self.with_kafka_sasl = with_kafka_sasl
         self.with_kerberized_kafka = with_kerberized_kafka

diff --git a/tests/integration/test_mysql_protocol/dotnet.reference b/tests/integration/test_mysql_protocol/dotnet.reference
@@ -0,0 +1,7 @@
+Openning connection...
+Connection openned!
+1
+Table created or exists
+2 rows inserted
+id=1, name=Alice
+id=2, name=Bob
diff --git a/tests/integration/test_mysql_protocol/test.py b/tests/integration/test_mysql_protocol/test.py
@@ -31,6 +31,7 @@
     user_configs=["configs/users.xml"],
     env_variables={"UBSAN_OPTIONS": "print_stacktrace=1"},
     with_mysql_client=True,
+    with_mysql_dotnet_client=True
 )
 
 server_port = 9001
@@ -899,3 +900,20 @@ def setup_java_client(started_cluster, binary: Literal["true", "false"]):
     ).format(
         host=started_cluster.get_instance_ip("node"), port=server_port, binary=binary
     )
+
+
+def test_mysql_dotnet_client(started_cluster):
+    node = cluster.instances["node"]
+
+    with open(os.path.join(SCRIPT_DIR, "dotnet.reference")) as fp:
+        reference = fp.read()
+
+    res = started_cluster.exec_in_container(
+        started_cluster.mysql_dotnet_client_docker_id,
+        [
+            "bash",
+            "-c",
+            f"dotnet run -- --host {node.hostname} --port {server_port} --username default --password 123",
+        ],
+    )
+    assert res == reference