May be useful to interface with some external program, e.g. I want to use `clickhouse-format` to beautify the queries for performance test reports.

For now, DDL dictionaries don't work for `clickhouse-local` at all (https://github.com/ClickHouse/ClickHouse/issues/22354)

We should do it through DDL, because the xml config route looks hopeless. `clickhouse-local` can't even load server's `config.xml` properly.
{
            return stream->getHeader();
        }
    private:
        Block readImpl() override
        {
            rethrowExceptionDuringReadIfNeeded();
            if (current_read_rows == rows_to_read)
                return Block();
            Block block;
            try
            {
                block = stream->read();
                current_read_rows += block.rows();
            }
            catch (...)
            {
                tryLogCurrentException(log);
                command = nullptr;
                throw;
            }
            return block;
        }
        void readPrefix() override