Method pin

src/storage/buffer_manager/buffer_manager.cpp:124–163

Important Note: Pin returns a raw pointer to the frame. This is potentially very dangerous and trusts the caller is going to protect this memory space. Important responsibilities for the caller are: (1) The caller should know the page size and not read/write beyond these boundaries. (2) If the given FileHandle is not a (temporary) in-memory file and the caller writes to the frame, caller should ma

// (3) If multiple threads are writing to the page, they should coordinate separately because they
// both get access to the same piece of memory.
uint8_t* BufferManager::pin(FileHandle& fileHandle, page_idx_t pageIdx,
    PageReadPolicy pageReadPolicy) {
    auto pageState = fileHandle.getPageState(pageIdx);
    while (true) {
        auto currStateAndVersion = pageState->getStateAndVersion();
        switch (PageState::getState(currStateAndVersion)) {
        case PageState::EVICTED: {
            if (pageState->tryLock(currStateAndVersion)) {
                if (!claimAFrame(fileHandle, pageIdx, pageReadPolicy)) {
                    pageState->resetToEvicted();
                    throw BufferManagerException("Unable to allocate memory! The buffer pool is "
                                                 "full and no memory could be freed!");
                }
                if (!evictionQueue.insert(fileHandle.getFileIndex(), pageIdx)) {
                    throw BufferManagerException(
                        "Eviction queue is full! This should be impossible.");
                }
#if BM_MALLOC
                DASSERT(pageState->getPage());
                return pageState->getPage();
#else
                return getFrame(fileHandle, pageIdx);
#endif
            }
        } break;
        case PageState::UNLOCKED:
        case PageState::MARKED: {
            if (pageState->tryLock(currStateAndVersion)) {
                return getFrame(fileHandle, pageIdx);
            }
        } break;
        case PageState::LOCKED: {
            continue;
        }
        default: {
            UNREACHABLE_CODE;
        }
        }
    }
}

#if defined(WIN32)
class AccessViolation : public std::exception {