Method readImpl

src/DataStreams/NativeBlockInputStream.cpp:100–216

Block NativeBlockInputStream::readImpl()
{
    Block res;

    const DataTypeFactory & data_type_factory = DataTypeFactory::instance();

    if (use_index && index_block_it == index_block_end)
        return res;

    if (istr.eof())
    {
        if (use_index)
            throw ParsingException("Input doesn't contain all data for index.", ErrorCodes::CANNOT_READ_ALL_DATA);

        return res;
    }

    /// Additional information about the block.
    if (server_revision > 0)
        res.info.read(istr);

    /// Dimensions
    size_t columns = 0;
    size_t rows = 0;

    if (!use_index)
    {
        readVarUInt(columns, istr);
        readVarUInt(rows, istr);
    }
    else
    {
        columns = index_block_it->num_columns;
        rows = index_block_it->num_rows;
    }

    for (size_t i = 0; i < columns; ++i)
    {
        if (use_index)
        {
            /// If the current position is what is required, the real seek does not occur.
            istr_concrete->seek(index_column_it->location.offset_in_compressed_file, index_column_it->location.offset_in_decompressed_block);
        }

        ColumnWithTypeAndName column;

        /// Name
        readBinary(column.name, istr);

        /// Type
        String type_name;
        readBinary(type_name, istr);
        column.type = data_type_factory.get(type_name);

        if (use_index)
        {
            /// Index allows to do more checks.
            if (index_column_it->name != column.name)