Method initialize

src/Storages/StorageFile.cpp:2118–2145

    }

    void initialize()
    {
        std::unique_ptr<WriteBufferFromFileDescriptor> naked_buffer;
        if (use_table_fd)
        {
            naked_buffer = std::make_unique<WriteBufferFromFileDescriptor>(table_fd, DBMS_DEFAULT_BUFFER_SIZE);
        }
        else
        {
            flags |= O_WRONLY | O_APPEND | O_CREAT;
            naked_buffer = std::make_unique<WriteBufferFromFile>(path, DBMS_DEFAULT_BUFFER_SIZE, flags);
        }

        /// In case of formats with prefixes if file is not empty we have already written prefix.
        bool do_not_write_prefix = naked_buffer->size();
        const auto & settings = getContext()->getSettingsRef();
        write_buf = wrapWriteBufferWithCompressionMethod(
            std::move(naked_buffer),
            compression_method,
            static_cast<int>(settings[Setting::output_format_compression_level]),
            static_cast<int>(settings[Setting::output_format_compression_zstd_window_log]));

        writer = FormatFactory::instance().getOutputFormatParallelIfPossible(format_name,
                                                                             *write_buf, metadata_snapshot->getSampleBlock(), getContext(), format_settings);

        if (do_not_write_prefix)
            writer->doNotWritePrefix();
    }

    String getName() const override { return "StorageFileSink"; }