Method initOutputFormat

src/Client/ClientBase.cpp:690–906

void ClientBase::initOutputFormat(const Block & block, ASTPtr parsed_query)
try
{
    if (!output_format)
    {
        /// Ignore all results when fuzzing as they can be huge.
        if (query_fuzzer_runs)
        {
            output_format = std::make_shared<NullOutputFormat>(std::make_shared<const Block>(block));
            return;
        }

        WriteBuffer * underlying_buf = nullptr;
        if (!pager.empty() && !isEmbeeddedClient())
        {
            if (SIG_ERR == signal(SIGPIPE, SIG_IGN))
                throw ErrnoException(ErrorCodes::CANNOT_SET_SIGNAL_HANDLER, "Cannot set signal handler for SIGPIPE");
            if (SIG_ERR == signal(SIGQUIT, SIG_IGN))
                throw ErrnoException(ErrorCodes::CANNOT_SET_SIGNAL_HANDLER, "Cannot set signal handler for SIGQUIT");

            ShellCommand::Config config(pager);
            config.pipe_stdin_only = true;
            config.terminate_in_destructor_strategy.terminate_in_destructor = true;
            config.terminate_in_destructor_strategy.termination_signal = SIGTERM;
            pager_cmd = ShellCommand::execute(config);
            underlying_buf = &pager_cmd->in;
        }
        else
        {
            underlying_buf = std_out.get();
        }

        /// Use the flush callback wrapper to prevent progress flickering
        std_out_wrapper = std::make_unique<FlushCallbackWriteBuffer>(
            underlying_buf,
            [this]()
            {
                /// If results are written INTO OUTFILE, we can avoid clearing progress to avoid flicker.
                if (need_render_progress && tty_buf && (!select_into_file || select_into_file_and_stdout))
                {
                    std::unique_lock lock(tty_mutex);
                    progress_indication.clearProgressOutput(*tty_buf, lock);
                }
                if (need_render_progress_table && tty_buf && (!select_into_file || select_into_file_and_stdout))
                {
                    std::unique_lock lock(tty_mutex);
                    progress_table.clearTableOutput(*tty_buf, lock);
                }
            }
        );

        WriteBuffer * out_buf = std_out_wrapper.get();

        select_into_file = false;
        select_into_file_and_stdout = false;
        String current_format = default_output_format;
        /// The query can specify output format or output file.
        if (const auto * query_with_output = dynamic_cast<const ASTQueryWithOutput *>(parsed_query.get()))