Remove data from cache

To remove data from cache, call these methods declared in allocator/CacheAllocator.h:

template <typename CacheTrait>
class CacheAllocator : public CacheBase {
  public:
    // Remove the item with the specified key.
    RemoveRes remove(Key key);

    // Remove the item pointed to by the specified handle.
    RemoveRes remove(const ReadHandle& handle);

    // Remove the first chained item pointed to by the parent handle.
    WriteHandle popChainedItem(WriteHandle& parent)
  ...
};

where RemoveRes is an enum class defined in allocator/CacheAllocator.h:

enum class RemoveRes : uint8_t {
  kSuccess,
  kNotFoundInRam,
};

For example, the following code removes an item with key "key1":

auto rr = cache->remove("key1");
if (rr == RemoveRes::kSuccess) {
  std::cout << "Removed the item with key \"key1\"" << '\n';
}

You can also remove the item as follows:

auto handle = cache->find("key1");
if (handle) {
  auto rr = cache->remove(handle);
  if (rr == RemoveRes::kSuccess) {
    std::cout << "Removed the item with key \"key1\"" << '\n';
  }
}

If you write the following three items to cache:

std::map<std::string, std::string> dict = {
  { "key1", "item 1" },
  { "key2", "item 2" },
  { "key3", "item 3" },
};
for (auto& itr : dict) {
  auto handle = cache->allocate(poolId, itr.first, itr.second.size());
  std::memcpy(handle->getMemory(), itr.first.data(), itr.second.size());
  cache->insertOrReplace(handle);
}

you can iterate and remove the three items:

For example:

for (auto itr = cache->begin(); itr != cache->end(); ++itr) {
  auto rr = cache->remove(itr.asHandle());
  if (rr == RemoveRes::kSuccess) {
    cout << "Removed the item" << '\n';
  }
}

Note that it.asHandle() returns the item handle for the iterator

Consider the following chained items:

To remove the first chained item (item 1), call the popChainedItem() method:

auto handle = cache->popChainedItem(parentItemHandle);
if (handle) {
  cout << "Removed the first chained item" << '\n';
}

If you remove the parent item, all its chained items are also removed:

rr = cache->remove(parentItemHandle);
if (rr == RemoveRes::kSuccess) {
  parentItemHandle->reset();
}