When I used ClickHouse's MaterializeMySQL feature to synchronize data from MySQL to ClickHouse, I had some problems. The Click House version I'm using is 20.10.3.30, and the MySQL version I'm using is 5.7.28-log.

The SQL statement I executed is as follows:
> SET allow_experimental_database_materialize_mysql = 1;
drop database if exists ck_test;
CREATE DATABASE if not exists ck_test ENGINE = MaterializeMySQL('x.x.x.x:3306', 'test', 'user', 'test');


After I executed the SQL statement, I saw the following information from the error log /var/log/clickhouse-server/clickhouse-server.err. Log:

> 2020.11.10 20:27:39.611578 [ 33057 ] {} <Error> MaterializeMySQLSyncThread: Code: 20, e.displayText() = DB::Exception: mysqlxx::UseQueryResult contains 4 columns while 2 expected, Stack trace (when copying this message, always include the lines below):

> 0. DB::MySQLBlockInputStream::MySQLBlockInputStream(mysqlxx::Pool::Entry const&, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&, DB::Block const&, unsigned long, bool) @ 0xe587457 in /usr/bin/clickhouse

> 1. DB::MaterializeMetadata::MaterializeMetadata(mysqlxx::Pool::Entry&, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&, bool&, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&) @ 0xdb1cbf3 in /usr/bin/clickhouse

> 2. DB::MaterializeMySQLSyncThread::prepareSynchronized(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&) @ 0xdaf8bf1 in /usr/bin/clickhouse

> 3. DB::MaterializeMySQLSyncThread::synchronization(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&) @ 0xdaf836a in /usr/bin/clickhouse

> 4. ? @ 0xdb1480d in /usr/bin/clickhouse

> 5. ThreadPoolImpl<std::__1::thread>::worker(std::__1::__list_iterator<std::__1::thread, void*>) @ 0x7b8963d in /usr/bin/clickhouse

> 6. ? @ 0x7b8d153 in /usr/bin/clickhouse

> 7. start_thread @ 0x7dd5 in /usr/lib64/libpthread-2.17.so

> 8. __clone @ 0xfdead in /usr/lib64/libc-2.17.so

>  (version 20.10.3.30 (official build))


Does anybody have a problem like this?
{
    Block header{
        {std::make_shared<DataTypeString>(), "File"},
        {std::make_shared<DataTypeUInt64>(), "Position"},
        {std::make_shared<DataTypeString>(), "Binlog_Do_DB"},
        {std::make_shared<DataTypeString>(), "Binlog_Ignore_DB"},
        {std::make_shared<DataTypeString>(), "Executed_Gtid_Set"},
    };
    MySQLBlockInputStream input(connection, "SHOW MASTER STATUS;", header, DEFAULT_BLOCK_SIZE);
    Block master_status = input.read();
    if (!master_status || master_status.rows() != 1)
        throw Exception("Unable to get master status from MySQL.", ErrorCodes::LOGICAL_ERROR);
    data_version = 1;
    binlog_file = (*master_status.getByPosition(0).column)[0].safeGet<String>();
    binlog_position = (*master_status.getByPosition(1).column)[0].safeGet<UInt64>();
    binlog_do_db = (*master_status.getByPosition(2).column)[0].safeGet<String>();
    binlog_ignore_db = (*master_status.getByPosition(3).column)[0].safeGet<String>();
    executed_gtid_set = (*master_status.getByPosition(4).column)[0].safeGet<String>();
}
void MaterializeMetadata::fetchMasterVariablesValue(const mysqlxx::PoolWithFailover::Entry & connection)