Add run_async method to SentenceWindowRetriever

[fkdosilovic]

Is your feature request related to a problem? Please describe.
I'm trying to minimize the number of components in my RAG retrieval pipeline that rely on running in the threadpool to be async compatible. It looks like that the SentenceWindowRetriever could easily (maybe I'm missing something) support run_async method by relying on the document_store.filter_documents_async method.

Describe the solution you'd like
Add the run_async to SentenceWindowRetriever that relies on document_store.filter_documents_async method.

Describe alternatives you've considered
The most general solution is already implemented in the library itself - run the component in a threadpool. I don't know any other good solutions.

Additional context

1. I saw the internal implementation of SentenceWindowRetriever.run method and I realize that most processing/work is being done inside the component itself, but that doesn't mean that the component should not be fully async friendly.
2. I did not find any discussion in the previous PRs related to SentenceWindowRetriever that comment/discuss why the run_async is not implemented.
3. I can work on the PR.

[julian-risch]

Hi @fkdosilovic Thank you for your feature suggestion! I agree that there is no good reason why the run_async is not implemented.
We would appreciate your help! I recommend to have a look at our contributing guidelines: https://github.com/deepset-ai/haystack/blob/main/CONTRIBUTING.md
Relying on document_store.filter_documents_async sounds good to me. For reference, run_async in InMemoryEmbeddingRetriever is a minimal example: https://github.com/deepset-ai/haystack/blob/main/haystack/components/retrievers/in_memory/embedding_retriever.py#L197
Looking forward to your pull request!

By the way, FilterRetriever and AutoMergingRetriever don't have a run_async implementation either. If anyone sees demand for that, feel free to open a similar GitHub issue.

[cmnemoi]

Hello @julian-risch, I opened a PR for this issue : #9895