Fix: use std::visit to replace std::get_if

[Light-City]

The destructor of dataset is not well written to release memory. We can use visit to simplify the code.

before:

{
                auto ptr = std::get_if<0>(&x.second);
                if (ptr != nullptr) {
                    delete[] * ptr;
                }
            }
            {
                auto ptr = std::get_if<1>(&x.second);
                if (ptr != nullptr) {
                    delete[] * ptr;
                }
            }
            {
                auto ptr = std::get_if<2>(&x.second);
                if (ptr != nullptr) {
                    delete[] * ptr;
                }
            }
            {
                auto ptr = std::get_if<3>(&x.second);
                if (ptr != nullptr) {
                    if (is_sparse) {
                        delete[](sparse::SparseRow<float>*)(*ptr);
                    } else {
                        delete[](char*)(*ptr);
                    }
                }
            }

after:

for (auto&& x : this->data_) {
            std::visit(
                [](auto&& arg) {
                    using T = std::decay_t<decltype(arg)>;
                    if constexpr (std::is_same_v<T, const float*> || std::is_same_v<T, const size_t*> ||
                                  std::is_same_v<T, const int64_t*>) {
                        delete[] arg;
                    } else if constexpr (std::is_same_v<T, const void*>) {
                        delete[] (char*)(arg);
                    }
                },
                x.second);

[github-actions[bot]]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions. Rotten issues close after 30d of inactivity. Reopen the issue with /reopen.

[Light-City]

/reopen

[github-actions[bot]]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions. Rotten issues close after 30d of inactivity. Reopen the issue with /reopen.

[github-actions[bot]]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions. Rotten issues close after 30d of inactivity. Reopen the issue with /reopen.

[github-actions[bot]]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions. Rotten issues close after 30d of inactivity. Reopen the issue with /reopen.