Add sort arg to JoinAnswers (#2436)

* Add sort arg to JoinAnswers

* Update Documentation & Code Style

* Change naming and docstring

* Update Documentation & Code Style

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>

docs/_src/api/api/other.md

@@ -70,7 +70,7 @@ A node to join `Answer`s produced by multiple `Reader` nodes.
 #### JoinAnswers.\_\_init\_\_
 
 ```python
-def __init__(join_mode: str = "concatenate", weights: Optional[List[float]] = None, top_k_join: Optional[int] = None)
+def __init__(join_mode: str = "concatenate", weights: Optional[List[float]] = None, top_k_join: Optional[int] = None, sort_by_score: bool = True)
 ```
 
 **Arguments**:
@@ -81,6 +81,9 @@ of individual `Answer`s.
 adjusting `Answer` scores when using the `"merge"` join_mode. By default, equal weight is assigned to each
 `Reader` score. This parameter is not compatible with the `"concatenate"` join_mode.
 - `top_k_join`: Limit `Answer`s to top_k based on the resulting scored of the join.
+- `sort_by_score`: Whether to sort the incoming answers by their score. Set this to True if your Answers
+are coming from a Reader or TableReader. Set to False if any Answers come from a Generator since this assigns
+None as a score to each.
 
 <a id="route_documents"></a>
 

haystack/json-schemas/haystack-pipeline-master.schema.json

@@ -2742,6 +2742,11 @@
             "top_k_join": {
               "title": "Top K Join",
               "type": "integer"
+            },
+            "sort_by_score": {
+              "title": "Sort By Score",
+              "default": true,
+              "type": "boolean"
             }
           },
           "additionalProperties": false,

haystack/nodes/other/join_answers.py

@@ -10,7 +10,11 @@ class JoinAnswers(BaseComponent):
     """
 
     def __init__(
-        self, join_mode: str = "concatenate", weights: Optional[List[float]] = None, top_k_join: Optional[int] = None
+        self,
+        join_mode: str = "concatenate",
+        weights: Optional[List[float]] = None,
+        top_k_join: Optional[int] = None,
+        sort_by_score: bool = True,
     ):
         """
         :param join_mode: `"concatenate"` to combine documents from multiple `Reader`s. `"merge"` to aggregate scores
@@ -19,6 +23,9 @@ class JoinAnswers(BaseComponent):
             adjusting `Answer` scores when using the `"merge"` join_mode. By default, equal weight is assigned to each
             `Reader` score. This parameter is not compatible with the `"concatenate"` join_mode.
         :param top_k_join: Limit `Answer`s to top_k based on the resulting scored of the join.
+        :param sort_by_score: Whether to sort the incoming answers by their score. Set this to True if your Answers
+            are coming from a Reader or TableReader. Set to False if any Answers come from a Generator since this assigns
+            None as a score to each.
         """
 
         assert join_mode in ["concatenate", "merge"], f"JoinAnswers node does not support '{join_mode}' join_mode."
@@ -31,6 +38,7 @@ class JoinAnswers(BaseComponent):
         self.join_mode = join_mode
         self.weights = [float(i) / sum(weights) for i in weights] if weights else None
         self.top_k_join = top_k_join
+        self.sort_by_score = sort_by_score
 
     def run(self, inputs: List[Dict], top_k_join: Optional[int] = None) -> Tuple[Dict, str]:  # type: ignore
         reader_results = [inp["answers"] for inp in inputs]
@@ -40,12 +48,13 @@ class JoinAnswers(BaseComponent):
 
         if self.join_mode == "concatenate":
             concatenated_answers = [answer for cur_reader_result in reader_results for answer in cur_reader_result]
-            concatenated_answers = sorted(concatenated_answers, reverse=True)[:top_k_join]
+            if self.sort_by_score:
+                concatenated_answers = sorted(concatenated_answers, reverse=True)
+            concatenated_answers = concatenated_answers[:top_k_join]
             return {"answers": concatenated_answers, "labels": inputs[0].get("labels", None)}, "output_1"
 
         elif self.join_mode == "merge":
             merged_answers = self._merge_answers(reader_results)
-
             merged_answers = merged_answers[:top_k_join]
             return {"answers": merged_answers, "labels": inputs[0].get("labels", None)}, "output_1"
 
@@ -59,5 +68,8 @@ class JoinAnswers(BaseComponent):
             for answer in result:
                 if isinstance(answer.score, float):
                     answer.score *= weight
+        merged_answers = [answer for cur_reader_result in reader_results for answer in cur_reader_result]
+        if self.sort_by_score:
+            merged_answers = sorted(merged_answers, reverse=True)
 
         return sorted([answer for cur_reader_result in reader_results for answer in cur_reader_result], reverse=True)