Method read

src/DataStreams/NativeBlockInputStream.cpp:233–266

}

void IndexForNativeFormat::read(ReadBuffer & istr, const NameSet & required_columns)
{
    while (!istr.eof())
    {
        blocks.emplace_back();
        IndexOfBlockForNativeFormat & block = blocks.back();

        readVarUInt(block.num_columns, istr);
        readVarUInt(block.num_rows, istr);

        if (block.num_columns < required_columns.size())
            throw Exception("Index contain less than required columns", ErrorCodes::INCORRECT_INDEX);

        for (size_t i = 0; i < block.num_columns; ++i)
        {
            IndexOfOneColumnForNativeFormat column_index;

            readBinary(column_index.name, istr);
            readBinary(column_index.type, istr);
            readBinary(column_index.location.offset_in_compressed_file, istr);
            readBinary(column_index.location.offset_in_decompressed_block, istr);

            if (required_columns.count(column_index.name))
                block.columns.push_back(std::move(column_index));
        }

        if (block.columns.size() < required_columns.size())
            throw Exception("Index contain less than required columns", ErrorCodes::INCORRECT_INDEX);
        if (block.columns.size() > required_columns.size())
            throw Exception("Index contain duplicate columns", ErrorCodes::INCORRECT_INDEX);

        block.num_columns = block.columns.size();
    }
}

}