Method Index

cactus/engine/engine_index.cpp:34–126

    }

    Index::Index(const std::string& index_path, const std::string& data_path, size_t embedding_dim):
        index_path_(index_path), data_path_(data_path), embedding_dim_(embedding_dim),
        index_entry_size_(IndexEntry::size(embedding_dim)), num_documents_(0),
        index_fd_(-1), data_fd_(-1),
        mapped_index_(nullptr), mapped_data_(nullptr) {

        bool index_exists = (access(index_path.c_str(), F_OK) == 0);
        bool data_exists = (access(data_path.c_str(), F_OK) == 0);

        if (index_exists != data_exists) {
            throw std::runtime_error("Index and data files must both exist or both not exist");
        }

        index_fd_ = open(index_path.c_str(), O_RDWR | O_CREAT, 0644);
        if (index_fd_ < 0) {
            throw std::runtime_error("Cannot open index file: " + index_path);
        }

        data_fd_ = open(data_path.c_str(), O_RDWR | O_CREAT, 0644);
        if (data_fd_ < 0) {
            close(index_fd_);
            throw std::runtime_error("Cannot open data file: " + data_path);
        }

        auto cleanup_and_throw = [this](const std::string& msg) {
            close(index_fd_);
            close(data_fd_);
            throw std::runtime_error(msg);
        };

        struct stat index_st, data_st;
        if (fstat(index_fd_, &index_st)) {
            cleanup_and_throw("Cannot get index file size: " + index_path);
        }
        index_file_size_ = index_st.st_size;

        if (fstat(data_fd_, &data_st)) {
            cleanup_and_throw("Cannot get data file size: " + data_path);
        }
        data_file_size_ = data_st.st_size;

        if (!index_exists) {
            index_file_size_ = sizeof(IndexHeader);
            data_file_size_ = sizeof(DataHeader);

            if (ftruncate(index_fd_, index_file_size_) != 0) {
                cleanup_and_throw("Failed to resize index file");
            }

            if (ftruncate(data_fd_, data_file_size_) != 0) {
                cleanup_and_throw("Failed to resize data file");
            }
        }

        mapped_index_ = mmap(nullptr, index_file_size_, PROT_READ | PROT_WRITE, MAP_SHARED, index_fd_, 0);
        if (mapped_index_ == MAP_FAILED) {
            cleanup_and_throw("Cannot map file: " + index_path);
        }