Zoltan Fedor 408d8e6ff5
Enable the JoinDocuments node to work with documents with score=None (#2984)
* Enable the `JoinDocuments` node to work with documents with `score=None`

This fixes #2983

As of now, the `JoinDocuments` node will error out if any of the documents has `score=None` - which is possible, as some retriever are not able to provide a score, like the `TfidfRetriever` on Elasticsearch or the `BM25Retriever` on Weaviate.
THe reason for the error is that the `JoinDocuments` always sorts the documents by score and cannot sort when `score=None`.

There was a very similar issue for `JoinAnswers` too, which was addressed by this PR: https://github.com/deepset-ai/haystack/pull/2436
This solution applies the same solution to `JoinDocuments` - so both the `JoinAnswers` and `JoinDocuments` now will have the same additional argument to disable sorting when that is requried.

The solution is to add an argument to `JoinDocuments` called `sort_by_score: bool`, which allows the user to turn off the sorting of documents by score, but keeps the current functionality of sorting being performed as the default.

* Fixing test bug

* Addressing PR review comments

- Extending unit tests
- Simplifying logic

* Making the sorting work even with no scores

By making the no score being sorted as -Inf

* Forgot to commit the change in `join_docs.py`

* [EMPTY] Re-trigger CI

* Added am INFO log if the `JoinDocuments` is sorting while some of the docs have `score=None`

* Adjusting the arguments of `any()`

* [EMPTY] Re-trigger CI
2022-08-11 10:43:25 +02:00
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