**Describe the situation**

```
SELECT * FROM test.hits INTO OUTFILE 'dump.csv' FORMAT CSV

8873898 rows in set. Elapsed: 32.487 sec. Processed 8.87 million rows, 8.46 GB (273.15 thousand rows/s., 260.42 MB/s.)
```

is bounded by single CPU core. Too slow :(
&& (0 == strcmp(arg, "--file") || 0 == strcmp(arg, "--name") || 0 == strcmp(arg, "--format")
                || 0 == strcmp(arg, "--structure") || 0 == strcmp(arg, "--types")))
        {
            if (arg_num + 1 < argc)
            {
                external_tables_arguments.back().emplace_back(arg
                ++a
                arg = argv[arg_num];
                external_tables_arguments.back().emplace_back(arg
            }
            else
                break;
        }
        else
        {
            in_external_group = false;
            /// Parameter arg after underline.
            )
            {
                const char * param_continuation = arg + strlen("--param_"
                const char * equal_pos = strchr(param_continuation, '='
                if (equal_pos == param_continuation)
                    throw Exception("Parameter name cannot be empty", ErrorCodes::BAD_ARGUMENTS
                if (equal_pos)
                {
                    /// param_name=value
                    quee(String(param_continuation, equal_pos), String(equal_pos + 1)
                }
                else
                {