The exists() method is not an abstract method and so doesn't have to be implemented. The original SharedMemoryDataset was wrapped around MemoryDataset directly so I guess that's why the warning wasn't triggered before https://github.com/kedro-org/kedro/pull/3332/files#diff-cc4e916905ba553d257700ff851973772c0d77018d7673a2c4b22f309d8c3e46. IMO we can just ignore this.

@merelcht Haven't look into this in details, would the alternative be changing that WARNING message to INFO instead?

Reported again recently: #4060

Updated the scope to double check where exists is called and if it makes sense to implement this method on SharedMemoryDataset.

Also related: #4078

Hi, I investigated this for a bit and I believe the issue is that SharedMemoryDataset delegates most methods to the underlying MemoryDataset via __getattr__.

However, __getattr__ is only called for attributes that do not exist on the object and since SharedMemoryDataset inherits AbstractDataset._exists __getattr__ is never called.

We could implement _exists on SharedMemoryDataset, we would have to handle the case where self.shared_memory_dataset is None (return False in this case?):

class SharedMemoryDataset(AbstractDataset):
    ...
    def _exists(self) -> bool:
        if not self.shared_memory_dataset:
            return False
        return self.shared_memory_dataset.exists()

I'm happy to submit a PR implementing this:)