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?
write_data_to_column(casted_decimal_64_column, Decimal64(), Decimal64());
        else if (ColumnDecimal<Decimal128> * casted_decimal_128_column = typeid_cast<ColumnDecimal<Decimal128> *>(&column_to))
            write_data_to_column(casted_decimal_128_column, Decimal128(), Decimal128());
        else if (ColumnDecimal<Decimal256> * casted_decimal_256_column = typeid_cast<ColumnDecimal<Decimal256> *>(&column_to))
            write_data_to_column(casted_decimal_256_column, Decimal256(), Decimal256());
        else if (ColumnDecimal<DateTime64> * casted_datetime_64_column = typeid_cast<ColumnDecimal<DateTime64> *>(&column_to))
            write_data_to_column(casted_datetime_64_column, DateTime64(), DateTime64());
        else if (ColumnInt32 * casted_int32_column = typeid_cast<ColumnInt32 *>(&column_to))
        {
            for (size_t index = 0; index < rows_data.size(); ++index)
            {
                const Tuple & row_data = DB::get<const Tuple &>(rows_data[index]);
                const Field & value = row_data[column_index];
                if (write_data_to_null_map(value, index))
                {
                    if (value.getType() == Field::Types::UInt64)
                        casted_int32_column->insertValue(value.get<Int32>());
                    else if (value.getType() == Field::Types::Int64)
                    {
                        
                        const Int32 & num = value.get<Int32>();
                        casted_int32_column->insertValue(num & 0x800000 ? num | 0xFF000000 : num);
                    }
                    else
                        throw Exception("LOGICAL ERROR: it is a bug.", ErrorCodes::LOGICAL_ERROR);
                }
            }
        }
        else if (ColumnString * casted_string_column = typeid_cast<ColumnString *>(&column_to))
        {