Method handlePart

src/Core/ExternalTable.cpp:167–236

void ExternalTablesHandler::handlePart(const Poco::Net::MessageHeader & header, ReadBuffer & stream)
{
    /// After finishing this function we will be ready to receive the next file, for this we clear all the information received.
    /// We should use SCOPE_EXIT because read_buffer should be reset correctly if there will be an exception.
    SCOPE_EXIT(clear());

    const Settings & settings = getContext()->getSettingsRef();

    if (settings[Setting::http_max_multipart_form_data_size])
        read_buffer = std::make_unique<LimitReadBuffer>(
            stream,
            LimitReadBuffer::Settings{
                .read_no_more = settings[Setting::http_max_multipart_form_data_size],
                .expect_eof = true,
                .excetion_hint = "the maximum size of multipart/form-data. This limit can be tuned by 'http_max_multipart_form_data_size' setting",
            });
    else
        read_buffer = wrapReadBufferReference(stream);

    /// Retrieve a collection of parameters from MessageHeader
    Poco::Net::NameValueCollection content;
    std::string label;
    Poco::Net::MessageHeader::splitParameters(header.get("Content-Disposition"), label, content);

    /// Get parameters
    name = content.get("name", "_data");
    format = params.get(name + "_format", "TabSeparated");

    if (params.has(name + "_structure"))
        parseStructureFromStructureField(params.get(name + "_structure"));
    else if (params.has(name + "_types"))
        parseStructureFromTypesField(params.get(name + "_types"));
    else
        throw Exception(ErrorCodes::BAD_ARGUMENTS,
                        "Neither structure nor types have not been provided for external table {}. "
                        "Use fields {}_structure or {}_types to do so.", name, name, name);

    ExternalTableDataPtr data = getData(getContext());

    auto temporary_id = StorageID::createEmpty();
    temporary_id.table_name = data->table_name;

    auto resolved = getContext()->tryResolveStorageID(temporary_id, Context::ResolveExternal);

    StoragePtr storage;
    if (resolved)
    {
        LOG_TEST(getLogger("ExternalTablesHandler"), "Using existing table {} for external data", temporary_id.getNameForLogs());
        storage = DatabaseCatalog::instance().getTable(resolved, getContext());
    }
    else
    {
        LOG_TEST(getLogger("ExternalTablesHandler"), "Creating temporary table {} for external data", temporary_id.getNameForLogs());
        NamesAndTypesList columns = sample_block.getNamesAndTypesList();
        auto temporary_table = TemporaryTableHolder(getContext(), ColumnsDescription{columns}, {});
        storage = temporary_table.getTable();
        getContext()->addExternalTable(temporary_id.table_name, std::move(temporary_table));
    }